.I.G.C®S.E h i Prof. Dr. Fathy Abdel Galil - : ·. Chemistry IGCSE (Dr.rathyADC\el uatuJ Contents Ef'~ Topic L Topic 2. . To.pic 3. Topic 4. Topic 5. Topic 6 The particulate nature of matter .........•.....................................•. States of matter·.......... : ............................................................. . . partie . 1e theory ................................................................ . K.metJc Diffusion ............................................... , ............................... . Experimental technique ..•......................................................... Laboratory apparatus ................................................................. . Safety in laboratory .................................................................. .. Methods of purification ............................................................. .. Separation of mixtures ............................................................... ·. Chromatography ~ .................................................................... .. Atoms, elements and compounds .............................................•.. Atomic structure ..................................................................... . .Radioactive isotopes ................................................................ .. . Electron distribution ............................................. :.. ................. . lons and ionic bonds ................................................................. . Molecules and covalent bonds ..................................................... . Macromolecular (giant) structure .................................................. . Stiochiometry ........................................................... .'.......... .. Chemical formula .................................................................. ·.. . Chemical equations· .................................................................. . Chemical calculations .............................................................. .. The mole .............................................................................. .. Empirical formula and molecular formula ........................................ . 1 1 2 6 8 8 10 12 12 14 16 17 19 20 22 25 28 30 30 33 35 37 ·44 46 The periodic table ................................................................. .. Trends in group I [The alkali metals] ............................................. . Transitions elements ................................................................. . Trends in group VII [The halogens] ................. ·.............................. . Nobel gases .......................................................................... .. Test and collection of gases ......................................................... . Oxidation and reduction ............................................................. . 48 51 52 55 56 58 Electricity and chemistry [Electrochemistry] ................................. . Electrolysis ............................................................................ . Applications of electrolysis ........................................................ .. 6D 62 67 Chemistry IGCSE Topic 7. Topic 8. Topic9. (Dr.FathyAbdel Galil) Acids, bases and salts .-............................................................. . Acids ............................................................ , ...................... . Bases ................................................................................... . The pH scale .......................................................................... . 1vfaking salts ........................................................................... . Types of oxides ...................................................................... :. Identification of ions ................................................................. . 69 69 71 72 73 77 79 Metals and reactivity series ..................................................... ... Alloys .............. c •. : •.. ; •..••...•••..•.•..•••.•..•.•••.•••••••••..•..•..••.••••.••.•. R.eacfIVI"ty senes . ....................................................................... . Extraction of iron ................................................... ·.................. . Steel making .......................................................................... . Extraction of zinc ..................................................................... . Rusting ................................................................................. . 90 91 Chemical changes Production of energy ................................................................ . Electricity from chemical reactions .............................................. . 95 97 Topic 10. Chemical reactions ····································'····························· Speed of reactions ...................................................... . :........... . Reversible reactions ................................................................. . Chemical equilibrium ............................................................... . 81 81 83 88 89 99 99 106 106 Topic 11. Air and water •••........••..•..••.••.•.•..••..•••••..••••.•.•••..•••.•••••..•••..•••• Purification of water supply ...................................................... .. .. f. ·. ComposttiOn o atr ................................................................. .. Manufacture of ammonia .......................................................... . Fertilisers ................................................ : ............................ . Air pollution .......................................................................... . 108 108 109 Topic 12. Sulphur ............................................................................. . Making sulphuric acid ............................................................. . 116 Topic 13. Carbonates ........................................................ ,.................. 118 Topic 14. Organic chemistry ................................ ••.•...•.•••••• .•••..••••. .• ..... .. 120 111 ll2 113 117 - -·· ttg c.r )- f"i y w bo-U-Wg 0 0 .JS''fK. Iodine. Unlike solids ang liq~ids. but their volume is fixed.1- Chemistry IGCSE .Wg me.JDI 0 0 0 LIQUID u 0. on cool test~tube Sublimation This is the change of state from solid to vapour and back from vapour to solid without passing through the liquid state.i.. liquid or gas. GAS iodina cry<tal$ reform . mole_cules or ions. These may be atoms.Topic 1: [Dr. States of-Matter All matter can exist in three ·states. 6Jt. gases are easy to compress into · smaller size.I gentle heat heat solid iodine [dark grey solid] allow to cool iodine gas ------+solid iodine [purple vapour] Solid carbon dioxide behaves similarly.onde.. we can explain the way matter behaves. behaves like this purple Iodine vapour. Liquids have no fixed shape.solid.Wng so LID f W. for instance. They spread out (diffuse) to fill all the available space.up of tiny particles.eez. . Fathy Abdel Galil] .Jt6. Gases have no fixed shape or volume. lodine cry•tal• ---. THEPARTICULATENATUREOFMATIER All matter is made . Using the idea of parti?les. Solids have a fixed shape. The state of a substance can be changed by heating or cooling. . . ions or molecules)..·.:=: >--(-' :>--< --'. X !()"( .e. .J 4..': Arrangement and Movement Particles SOLIDS - LIQUIDS GASES ·')( )()J )( T)ll 'l... All matter is made up of very small invisible particles (atoms.olume]. The higher the temperature. .' Arrangement of Particles close together in a regular arrangement still close tog ether in an irregular arrangement particles far apart Movement of Particles only vibrate in their places can move around slowly free moving rapidly Kinetic Particle Theory 1... Fathy Abdel Galil) -2- Chemistry IGCSE :.-.r"[ ( )[ " J: "'[_ J: J[ 0 0 0 0 0 0 0· . 2. Using the idea of particles and kinetic theory. . the faster they move. 3. a gas can fill any v. there is relatively large distance between the particles. ..(Dr. we can explain the changes of states of matter and diffusion . . In a gas. The particles move all the time. They are free to move anywhere [i. Lighter particles move faster than heavier ones . .<..~~T~ a liquid is formed Mel. nrraan·a· o·' " . At the melt~g po~nt the part~cles v~brate so much that they oreak-aYay from the~r pos~t~ons.:thtg Po. hold~ng and form a heat boilino point slow-moving particles in liquid the particles move faster the particles get enough energy to escape Bo.g... i..the part~cles Th~s is heated.. They break away from the liqu~d po~nt...e. :a. 'offifi8§. .zn.... Pure substances have fixed and definite melting points and boiling points.Ung When a liqu~d move faster. ~ !he partici!"S vibcate.ln.. its particles get more energy and makes the liqu~d expand. Bo.Ung Po. melting point ·- . At the boiling get enough energy to overcome the forces them together. e. pure water boils at 100°C and freezes at 0°C... changes l~quid.3 - (Dr. ~ts part~cles ge~more ene..· changes into a gas.. The sol~d becomes a liquid. ".....e.:thtg When a sol~d ~s heated..<. heat heat at O:ffil. Fa thy Abdel Cali!) Chemistry IGCSE Changes of State Mel..t ~s ~nto a the temperature at wh~ch the sol~d melts.gy and v~brate more.. ~. Th~s makes the sol~d expand.DOG DQO: · "0'0' .t is the temperature at which the l~uids bo~l...: 'G ' . U_c..e . :.emembVt ~ .omplr. Fathy Abdel Cali!) Evaporation When left open to the atmosphere.. ..into a_ <. even b~W when a ~quid ~ Well the boLt£ng poLnt.i:.t to Jr.6 pa_c.tlw. ·If enough force is applied to the plunger.. But liquids and solids can not be compressed.u.t boiling oc.6 <. -This is called evaporation. the boiling poht.:ta_neou&.c.t{_cl. You c./'.Jti.a.:tuAe wfti__cJt . some particles of a liquid escape into the gas state.ung Vt. the particles get so close together that the gas turns into a liquid.ume. <..queezed oJr. The gM g ei:.:tuAe-.t.the pa_ll.a-Ut tempeJr. .maUVt vo.U..t evapo~on oc.u bt a_ gil<.4 - Chemistry l GCSE (Dr. gas compressed 0 0 0 0 0 0 0 0 inlo a smaller I'Oiume bq ptUhlng bt the p..a_n 6oJr.. c.. c.elr..empeJr. bu.e between the p/Vr.. Compressing a Gas plunoer pushed in 0 oas particles 0 0 0 0 0 lL_ 0 0 0 o o ThVte ~ a !_at a 6 . because their particles ara already close together.pon.tu elM Vt ••• 0 0 0 0 of-.. A poht./'.q a_t anq i:.a.cJLM lli:.e<./'.c.6ed . The rate of evaporation increases vith o c increasing temperature increasing surface area. ...e.. "3• -...........[1] ....temperature.. i!'(tJ ..............................6....... :... :............5 - Chemistry I GCSE (Dr...........?.: ... ~................................. Fa thy Abdel Gali!) Temperature changes when a solid is heated I I I I I I t 'Temperature boiling _ point }i____________ }! ~ boiling melting point T I...............lE.. substance state at room .. choose: (i} one substance which can be easily ccmpressed at room.ater liquid From the table.?........ (iii)' one substance which has a fixed shape at room temperature ...............•••1:"€\:....- '------y----' melting I I ' Time~ Qu. temperature carbon dioxide gas iron solid w.............Y.................... [1 J (ii) one substance which consists of particles which are far apart at room temperature.. .. ~---··············· .ction Look at the table..... \ \\• q(' •...... . c...tong .tube.l wheJLe they meet.U. The smaller the molecular mass the faster the rate of diffusion.t .t .5 Ammonia deffuses faster than hydrogen chloride.t. 2.) The g. c. seen mainly in gases and liquids.ked .· 4olu.n.60a. Why? . The red-brown bromine vapour spreads out to fill the gas jar. bromine vapour .luztion.oa. ' .e. e a.A .{. WoJtciJ. Whi.6 - (Dr.theJL end hydlt. nJLOm JtegioM o6 /U. Fathy Abdel Galil) Diffusion This is J. pu..6tju.ed bt hyd!toeh.to one end o6 b) A. In otheJt.oncen:tJtatiort . .Lxhtg pMeeM.a.onc. The bromine diffusion experiment: Bromine is a red-brown liquid which vaporises easily at room· bromine temperature... Some of the liquid is liquid '\ placed at the bottom of a sealed gas ~ jar.. 06 the . The particles in gases are moving faster than in liquids..n.<.the . I.. The rate of diffusion· depends on the molecular mass.{.ve.' . pu..<.<.<.n. .hlo!Ude ga.the o.to!Uc.ofton woo...to .t exactly .t g.de..a. The particles of one substance mix with and move through the particles of another. I. Diffusion goes until the mixture is· uniform..tube..n.oM On loWelL c..<.. i.n ammon.te 0 66 solid o6 ammonium chlo!Ude 6ai!Jn.(.piteac:Ung oat and m.. o66 ammon.t!-on a .gheJt..tong . c.to Jteg. ga.tUne. Diffusion of ammonia and hydrogen chloride a) Co.ton wool . calion wool soaked In · glass tubing eolian wool soaked In ammonia hydrochloric solution acid + Mr white solid forms here 17 HCI(g) -> NH CI (s) 4 36. Diffusion is fastest in gases.k. I.t i.t . :~'. · e6 d..ve.': '.ogen c.the movemen..tube.u.t g.{.t an pcvd-{.t. aud .Chemistry IGCSE .the <lame ..{. ..L~D..:-----~ i!t l •· o -. ' .. / .!~:r ··.".Ji!• 0 '<--..e..... ..'• • • • • • ""oro o '' bOtJhl ll /.. . r ...7 - 3UOI V1HJ3......li 9 o o • • "" o • • • • • • .\!Lt'JJ.•...1-t u.c-~r-- /- 4.· (l'lJJd i .:<·~t:. ..f ::.!fei:oloration will be eq#tlly distribute~ throughout the solution. "~t.1 \.(1..·~~ (j .:. ct~s i:of f!"" r:><h"">i <i..A f 1 •• The dia~ilaiiV':T'hows the diffusion of the exhau~ .SaJiv... when they meet the ~I. ·uhvc! riJiw biup-:1 '-!iizn!}b . ~~ U ~....{'par~ · i.__ _ _ _ _ _•.~ ~ iQ! 1\ 1'~ri:f.l •l ... . •Jo 4 ".t gases from a car~ol!~•. .! ... ../.:~J:q .-:---.(Y....~-!:l..·-' l'-------~--) "-----'· ...T .Th i·\) ~ .._~ • •. . ....--~./ - • • • • • • • .~!. . ' 0 q:n:.. .....~~. !! k. ··-~... \=· / '' . !.. '.'/ ..___./ ..'!I...i . H i.~~~"f""'t ..:. .f ' . :.~>-':..j\>J Q.....urple) are carefully ~ded to a beaker cdfit!Jifu'W~Ate~. ..-•..'If 'I ...:.·-~.. ~he observa#:ns _give a~ r/..:..1-~!--!!~~J. ··._ .l \1 -----· . up:0rr\8is'2or#s'ih 'air /~.39X3 li I! 3.!.V * • "• * * • t\ • "•j-*<'• ...JA T~~3Mi9.• • 1_. ~ H lI t\O/ 1 It is difficult?p explain t4~ above aiasetvations with. o o • ..-~--...•.ftli>~&pl. .a. h). ..:q) solutio).:.. ... . r~. ~ ( \---Ll \ 1.· G]/.i.. 1{:-.. '.ouf using the t'"'tes.t >:"' ._.B~!:> . -----· -~ _) = ··--" 1-<" ··-.~~.:: .•.tOO:) )/a!LL1 ·.a~!ll "'-":"''·1 .Nidence~or {he movem(:nt oj:farticles 1 m gases andHzquzds..!.srlairi .. t..\ I t : r .l'.... 1 -ll ! ·1-.. ~ t 1 ! '··-~--. Iffew dro~s of potassium manganat!:_. .:·•• 0 • • • o o • '-.-----. • • //...i .. -%:l[e __ some other_ examples of diffusion.. 1liiW blc•pil--V!ii!neb..•./ ~ · .:<..'... ""'lUI!!O?.OJfo~o ·.' z·dea o1..(p.:. .~. J.o o6·Uo.· u tap beaker conicnl flask measuring cylinder pipet to ~rette 6oiL a.8 - Chemistry fGCSE EXPERIMENTAL TECHNIQUE Laboratory apparatus ·:.Topic 2.u.lume. Fathy Abdel Galil) . (Dr.cClll<iLte mvw wUn9 o 6 vo.n burner thermometer --li<luld with Iowa: density liquid with . hlohor density {Oi!QS balance .bunae.d& mo~Lta.~L ~ watch glass evaporating baa in ~'"'"" funnei 6 6 crucibla and lid . A saturated A $Oiution is fonned when a rolute is dissolved by a solvent.: ---:....(0'\J v f. goo<(SO"lve!}Dror many solids. y ~ - . This is called a: solub!Iity curve. Most cqmpounds dissolve inore in hot water than in cold...gine stirring spatulas full of copper sulphate crystals into water. A saturated solution is one in which no more solute can dissolve at that temperature.. : .--e / / •<. Im3.. :rolution "is one that will dissolvt no more wlutc at that temperature. with increasing temperature. much inore solid could be dissolved in it. ~~-p""!v:" . 20 40 60 Temperature/"C 80 100 ...- c.... Solubility curves for various compounds D1 ~/. as more crystals are stirred in to the solution.-\ L) - ....cf_ .: 0> 8 / .te is dissolved in a saturated solution.h?::-4 I' /1 D~~<"t:>I~~..: . Fathy Abdel Galill Dissolving solids in water ~a. •ulphate cry :.. will dissolve in 100 g of water.. If the saturated copper sulphate solution were heated. This is called the solubility...tal._. At first it is easy to dissolve the solid in the water to make a solution...... Their solubility increases wjth increasing temperature. The solution·is saturated..... Making a solution saturated copper sulphate ro!ution water Is a more copper. .!'V~' l:l m ::. 150 c " !) ll · ·trate ~\UI1'\~ 100 r. 0 50 '- )f:-'' ' 0 4 - .. ~ copper sulphate Is a solute solvent + A solvent is the solute saturated solution solution liquid that docs A solute IS the substance that the dissolving.1 -Jute '. A graph can be plotted to show how the solubility of a compound changes . is dissolved. \\\ ?'<$9\1}~.( 25 0 / / .).g' 200 / 2m . Eventually.. Chemists often need to know exactly how much solu.Chemist•·y IGCSE (Dr.L L.. . The solubility of a solid in water is the number of grams of that solid that....'--'.. no more will dissolve. es include boiling. . r. • • • ~ • v •••••••••••• 0 •• 0 ••••••••••••••••••••••••••• 0 •• 0 •••• 0 . hydrogen ..16: d.. petrol .rtl c. ~. '. . evaporation.......ammable ethanol... If the ·solvent is water.ng agent potassium dichromate~ potassium manganate..£.. the·solution is called aqueous solution (aq)........... A concentrated solution is one which contains a high proportion of solute. bromine.... Other physical chan:.10 - (Dr..·?!: ~· .... A dilute solution is one which contains only a small proportion of solute.. . chlorine.i..Chemistry IGCSE .c.... Fathy Abdel Galil) Dissolving is an example of a phy¢..o..'~\ ..i.. {a) :tauc..... melting... How would you make a sample of sea water more concentrated 7 .'?f: .!:ange..f. 0 •• ·safety in the Laboratory Some chemicals are ~articularly hazardous..: {d) ......i'. These are pointed out by standard tiazard labels.....V e concentrated solutions of acids ~nd alkalis such as concentrated sulphuric acid {c) oucU.OIVW¢. carbon monoxide {b) C..... .. .................. electrical switches or chemicals look down a test tube that is being heated..Carrying out the experiments which involve toxic gases and strong smelling gases in fume cupboard or' in we'fl-ve'rlfilated laboratory.......~...............' 0 I -" l \ ?... .?~ 1• u· ~ ! I !· .....:................. This diagram shows a student working in a laboratory................Chemistry I GCSE (Dr.::.....·· ... I .............................. Fa thy Abdel Galil) ....................................................................................................... . ........................... ~-............... a 2- Wear gloves when doing experiments with corrosive substances 3- For heating a flammable liquid use a hot water bath......11 - Laboratory Rules for Working in a Laboratory DON'T DO e run in the laboratory o eat or drink in the lzbt:re...... .... I S arety pro bl em 1 ......................:::...........V\_ ...................... \....... .. Identify two safety problems In this scene..... ....R:?............................................................ or point it at anyone e keep bags and coat safely out of the way e tie up long hair and tuck in ties and loose clothing e wear goggles or safety glasses when doing experiments o keep your place tidy and wipe up spills of chemicals o ask if you are unsure about anything ..::o:........ [ 1] ............... •·•·.......l......::ory ill> piay with fire..................................:............................. §~~~-~~i~El_EE~~~~E~~~~-~ 1. :::-~...:::::..................'k\0 ..... I"~ l_ \_ ··~ ·urr>..... ·'C'.. ......·'I!...................~'......... ·.....!L"f. [1 1 ' Safety problem z ....... lZ - Chemistry IGCSE (Dr.n.Ud Mild (J.e.... the point at which crystals of solute will form on cooling the solution to room temperature and can then be f"iltered out. Fathy Abdel Galli) Methods of Purification 17'--filter paper · fimnel residue.f1__/ / .. ..J-salt solution A solution consists of a solut..c.e dissolved in a solvent..eifc!c"( I I ~ I __.te) Filtration The solid is left on the filter paper as the residue while the liquid passes through.te a. 6Mm a.tub. water evaporates and solid ·salt ·is left. and dried.) v •· · ••••••••'-r•:f·••••••••••·•••••••••••••••••••••••••••••••••••••••••••••••• v •••••••••••••••••••••••••••••••••••••••••••••••••••••••• ' .... . Uqr... i.Ud 6Aom a..utLon t:===::J-. ! ----- c .5o. ba.. a) To .. -~_.•.5epaJta....~'~ I · tripou· . t •••• ..6 o.) ~. - '%?~~~- :C..t I_ ' -::.f. By heating the solution.. b) To ob~ substance a. Just by pouring the liquid insoluble off from the solid._i \ ..s: 1n / gauze· --- of salt (sodium chloride) in K~~r water.::-.. u The solution is evaporated to the crystallization point. What method could be used to show the crystallising point had been reached • 'I' '""' -'r .5o... Sea water is a solution solution~-_____ evop oratlng :. ng.i.to acfU.Jolest paQ:· of column·--- mixture of ethanol and water.ttcr in pun distilled HEAt :iJJJo .e6 [alL bMk. e. m!. volatile).i.eta.g.e. is more lower temperatures.en polLc.e. Ant£-bump. The liquid with the lOI<er boiling point (ethanol) and distils over and is collected z ~8 ethanol vapour and water vapour reaches the top of the column 1 broka_n Porcelain HEAT first. added . Fathy Abdel Gal!!) a 4otution Distillation ------------ _ tharmometor When the solution ia boiled. sea water d} To 6 epaAaXe cold W.the.13 - Chemistry IGCSE c) To a 6olvent 4epaAaXe 6~om (Dr.teady bo-UJ. ones that mix together completely) may be separated by fractional distil~ thermometer lation provided that their boiling points are different.to .:a·tions of fractional distillation : a) The separation of liquid air into oxygen and nitrogen b) The separation of crude oil [petroleum] into useful fractions. the vapour passes down· a condenser where it is converted back to liquid and is collected as the distillate.Uqu)... 3 .eve 6.xJwc. The mixture in the flask is heated so that it boils.ng gMnui.. Both cold water In fractionating ---W~ column filled with tilc:ss rods go up the fractionating column. Ethanol has a lower boiling point Frt~ctlons collected at (78°C) than water (i.n} alLe. Important appli<. Cr.e.cL6 water Fractional distillation ----------------------Miscible liquids (i. . the solvent changes to vapour. .Filter paper 0 r 0 small .the .~.om~og~... water.--.. E..14 - {Dr.nt) so that the position....t Jt... iLn.spot of the solution containing the mixture The.... . Fathy .. ..o ub.d .o..cM:.-a public movement of solvent 1---------------f analyst can firid out whether a dy_e used iri . known dyes.food is a permitted one f or an 'illegal' one. •e.. colouring.. substance will produce.---"----. .the.the .ma. ...W .t nuu.o.{.opa.Abdel Galil) Chemistry lGCSE e. .ove ..n.. C.g U!.t. dlurWn....atilig ILge.. but . and pure chemicals B. <> otve.g..o po. A ...i...the.l. 0. a 6 LL!.the bofvent - is placed near the end of the filter Solvcnl paper...... it can be used to_separate the dyes in ink..Uh ink ? ····~--~·-·······················································-···· ..Miubie. and it contains dyes 1 C1 and 1 A D'·. 8 c 0 ED samples -of dye A. ~ . Example. Chromatography can also be used to separate calaunle46 substances.. of the s.. .w pe........ The end of the paper is dipped into a solvent (e.ILM ~ ...n...) Clvr.pots.n. added along !his line as shown I 6 a.t Why mU!.ta.togJutphy 3 A dye used in food colouring f--. spots of various consti. .... A single p~e..taJLt..the...ng -Une.o.. ab...--------f can be ide:ntified by chromategraphing it alongside some pure.Wg clvr..... ..M on. ..tevel o 6 ...ama...tuents of the mixture will be collected at di{ferent distances above the original spot. In this way.g.in this case the paper must be sprayed with another chemical [tac.l e._.. e. 6po.d nat w.t ..{... As the solvent rises up. . be.. The finished paper is called clvr..ta.e.. .U me.Jt. It can also be used to identify additives in foods such as flavouring and. V<-" .l. ethanol)... can be seen. The figure shows that dye: 'A' is a mixture.nce.t be.only one.n.ti...omCLtogJutphq Paper chromatozraphy is used to separate a ' mixture of similar solids dissolved in a 0 : solvent.. . Impurities make melting points lower and boiling points higher.c.ta....ng po~. The WCLte1t .Utg po. A substance is not pure when it has other things mixed with it.L c.6ea.LUng po-Ln:t w.. 6Meze<> at a.'\" ? '.... .e -L....Ung po..>.. . . ...\. f I ' I 9 ' 1 fruit drink f 2 3 4 colourings 5 Which two colourings are in the fruit drink? A 1 and4 8 1 andS 2 and3 C @ 2and5 Testing the purity of a substance A puJLe substance has nothing else mixed with it...6!Lb. m me. For example..n.U. drugs must be tested for purity before they are sold.LU. these are called irup~e6. ~ •• ~--u··························::.. ..e' ...... ...··t···I <2Y'- \\..nc...6ee 8'--~> \:... I. I o a...6 no:t puJte. az ~o\__ eo'" -to a..6.. .ng puJLUy i....y o 6 :te<>:ti..omatog1taphy c..bou:t -2'C a.... ...6 me-tUng po-i..the .ta.en 6Jtom ..6 U pWLe ? No 1 .nd boili at 70 1"C.6 puJte..an be Ul>ed :to .nc... ··································~··········--··~ ..~ 0"-·fl"'--' • • • 'l.~ s"""'"\..- 15 - (Dr..6:ta.11-t. 2.......nc.t be d.::: ·. ~ v. PuJLe .....>ub.i.:the1t wa...ta.. Ano.6:ta.. .>ub... Why ? Gu:. < \_ o·~\.. Impurities might harm the patient.ill:t otr_ bo. ... . Chemists often need to know if a substance is pure....U.6ub. 7. ".R....u_\::\::::"<>" J. <:>'0...j'""""'"" .) ". :to meMuJte :the .nd bo.."-'-'S': -.n:t otr_ ba. Chlr. Fathy Abdel Galil) Chemistry IGCSE The diagram shows a chromatogram used to find out which colourings are in a fruit drink.o \'__ ~'y.e -i.i.i..e<> have de6-Lnile me.o oe1len:t 6Jtam :the known. How \\c-..Uhtg po~ a...... \... ..1\ : ~f'~::·ze :C.. . air or sea water. A mixture has the properties of the substances in it and can be separated by the methods described in Topic 2. A comparison of the properties of metals and non-metals Property Metal Non-metal state at room temperature solid except mercury (liqu1. There are over 100 elements which are grouped into two main classes metals and n'on-me tals. e. e.ifficult to classify Because they have some metallic and some non-metallic pro- perties. except graphite is a substance made up· of two or more elements chemically combined together. water or carbon dioxide.break into pieces poor or none. Fathy Abdel Cali!) ATOMS. Compounds and Mixtures Element : is a substance which cannot be split up. aluminium or sulphur. Mixture consists of two or more elements or compounds which have not been chemically combined. There are a few elements which are d. gases and one liquid (bromine) melting point high except alkali metals low except carbon and silicon appearance shiny dull .g. A compound has properties different from those of its elements. Compound effect of hamme ring easily shaped electrical and heat conductivity good brittle .g.16 .. (D1·.g. e..d) solids. ELEMENTS AND COMPOUNDS Elements. Chemist1·y I GCSE Topic 3. There are only 22 non-metals. Most of elemen t·s are metals. It contains atoms of only one type. .. • • ••••••• .on is a negatively charged particle.. (p + n) Atomic No.. An elec.li.... . Cha... (p) X (symbol of the element) Ato~e nu. ..tono MM<l numbe... o6 o6 neu. · · 12c 6 .. • . The nucleus is made up of two types of particles p. Ma... (IU... surrounded by electrons...on is a neutral..i.. +1 1 1 PILO..v e......tort Neu.particle (uncharged)..6c. Ato~e (p.~t : (A) is the total number of protons and neutrons in ari atom. where all·the positive charge and most of the mass of the atom is concentrated..... . Fathy Abdel Galil) Atomic Structure Atoms consist of a minute nucleus..Jr.tono and neubr..~t = nu... Work out the numbers of sub-atomic particles [protons.mbe.....= nu.tono + nu. n = " .. Question . e = . • .....li... Mas~ No.....tic. A.tJton (Z) is the number of protons in the nucleus......ono No... with mass equal to that of a proton.Jt..ono.. the mass of the electron is so small that it can often be ignored...M Pa..li. ..mbeJt p!W....Lcteon) nu. neutrons and electron J of the atoms of the following element..li.. of neutrons = Mass no.te.~t .ton is a positively charged particle.t...g e...17 - Chemistry IGCSE (Dr.ti.bwn 0 -1 1/1810 Etec......ton) nu.Atomic no.~to. Atoms are electrically neutral because: number of +ve protons = number of -Ne electrons.. Rela. A pJto.o....mbe.. • •• • •• • ..t...mbe.mbeJt : auiL-a:LomLc.... p c 56 26Fe.mbeJt on pM.....neut..li. Ma.. . . .the <..... ... . ...do i.....o IU .......e... ~H..Jtbon Carbon has 3 isotopes f.... = Nwnbvr.. " .... . . ... .. bu....... ... neu:tJr..... with two neutrons... ....ent 0 {.. . nutM numb Vt6 • I<>o:topeo o6 hydJwgen Hydrogen has 3 isotopes () Most hydrogen atoms are like this. .. . ..... .....tc. o6 dec...X. ...............a. 0 And some are like this... . It is called deuterium....... .. .. _ ....66 nwnbvr...... ..tom<> o6 the <1 am.thvr....!a... .. cU66vr.aue ..18 - Chemistry !GCSE (Dr. . . .. ... ...... ........ [2D] 1 ......... .bta JU = Nwnbvr..oo:topu h. It has one neutron.... " [C] ... .. .o JU [AJ is called = [A] ( B] ... . ................. .. . .. ..... ....... el-ement. .. IM:topu o6 c... carbon~l2.. ULU:h the <....... What do you think [BJ· and [CJ are called ? . ... ..toJU = Nwnbvr.........tom... . ...... cU£ {. It is an orcl......... Vtent numb eM 0 6........ ............ ..c... o6 plto.......... .ame a............in o.. wo... ... nwnbvr.. o6 neu:tJr.. " .inarj hydrogen atom with no neutron.. It is-called tritium.:. 1 H. ...Z... Fathy Abdel Cali!) Isotopes I<> o:to p eo aJt.. . ........ .. [fT] Isotopes of an element have the same chemical properties. ......... ..e a.... ...... ame numb eM pM:to IU bu............· ..... .. l H...X.. ..·......... 0 But a few' are like this.. using controlled doses of gamma radiation from cobalt-60. Some us. Fissiori. 2. When they are bombarded by neutrons.t€!.p.g.eitc.· + 37 X 25/100'= '--· • · .g. 2- Sterilising medical equipments I!1~~~-~~ ' e.e is0tepes (such a5.e_s : Me. anti! gamma r] in @faer · to Ille mere . ·· . they emit certain types of radiatl&n ·[alJ!lha a.· .atomic mass. chlorine consists..iS@toges takiug· into ace0unt their proporticms.A : --------------. am<Junt of heat energi (nuclear · energy) wich can be used f<Jr generatio_:il ef electricity [nuclear pewer stations] • Nu"clear fission b done in a rw. Cance-r treatment : Tumors can be.etive . · For example. g. .haye tmstable nuclei.i@a. ) ( 235u as a source of_ ener!iJ)'· Nuclear fission Some radioactive isotepes are used as nuclear fuels e..19 - Chemistry !GCSE (Dr. Their proportions a~e--75% of: ~fCJ: an. 1- e. 1.<! 25! of 37c1. ·Sem. destroyed.u] is theaverage:ma&oEits.:toJr.dea. Nuc Iear Power . 17 The relative atomic mass of chlorine· will be: 35-~.e. ·.iso..staDle. of uraniuni-235 atom produces a fw{Je. The relativ.cU.Detecting leaks in water pipes. The splitting of an at<Jm is called nuclear fission..Jt lr.. Fa thy Abde! Galli) Relative atomic masses Host elements contain a mixture of isot<>pes •..tri~um ami car!D0n-14].aL 1M e. of the etement[f.c. they s-f)llt ·=!Jtto sutaller at·oms.75/1@0 Radioactive Isotopes . Uranium-235. "fueta ~. This explains why their relative atomic masses are·noz whole numbers..· Checking the thickness of paper during manufacture.es ~of r:ad.-of i:wo isotol'es with mass ·numbers of 35 and 37.. ta.ve. 7J Uec.c:Uve bec.the :t/Wui 8 04 7. .::t e.!Je . Fluorine.6.they Jtea.c.1 2.anged i.i.t o.the nex:t llheU. 'Lt <1 eemb .n.temen.8. 2) Ea.tha.u. Jtea.nd .cl' c. chlorine and bromine (group VII) have 7 electrons in their outer shell. The nobel gM eo Me .6 go J. sodium and potassium-(group I) have one electron in their outer shell.he.onto:i.d :to f:. 8.d ea.7 2·.U:h .n.8. ve:Jty (Uillea. They w. What is special about· the.e}()_eo o6 .6 heW. o.8 Na Mg Al Si p s Cl Ar 2.ofJ e..8.2 2.ec»to n.b. .ll 6..to 6oJUn mo..t.y w. e ..8. _. We c.nobel gases 7 The nobel gMeo Me. a.o.ll. Jithiunl. a.n:to .ll. .t.a.tt llheUb.to to {.u..eu.7 2.. Li.ve) bec.:teJr.the uc.6.8.U.flo on. 3J The .n.eme.ec.c.tl. When U .20 - Chemistry IGCSE a.ompound.U not joht up wi.e.tMn.ul.5 2.U¢ aAOW1d .b.8.a.4 • The outer shell is called the valency shell and the electrons of the outer shel! are the valency electrons.3 2. . .they do not ha.8.eo • NoJt wLU .te (ullltea.u.ec.oJUn c..the nu..onctude .4 2.1 2.W t]u. The first twenty eLements in the Periodic Table and their electronic structures ~~e H I Li Be B: c N 0 F Ne · 2.tha.auJ.aJr.tec..b:t .2 .tl.theJr.the nucte. Fathy Abdel Galil) .n onty hold :two e..5 2.f.h llheU c.!'llleJJb.:2.the e.6 .U Me Jtea.L5 6JM:t• .6 2. e.c. .2 2. ..iJr.ve {. 2.oul.8.8 K Ca 2. e..il.6heU ne. 4 J · The fJ. • Elements of the same group in the periodic table contZin the same number ofelectrons iii their outer shelL For example.theJr.Jty a.a.1 2.v e ·n uU ou.mUed 1tW11bVT.o nd 8 and .tft ea.t1Wn.(Dr.6 2.t.n only c.y 6uU <>hellll.6 Me IVUl.tMn.3.clt o.8.they ha.8.nd get onf.8.8. .theJr.cl.U.6 heU c..t.t :t6 . 10 @ @ @ @ @ @ I Mg I 2.3 Aluminium atomic no. B. 2. "' u... 12 8 Boron @ @ .8.5 2.:.c The electronic coftfigura!ion of aluminium is 2. u 2. 8.B.6 2. 0. 8. 8 0 Fluorine atomic no.8 Cl . E Q) . 1 "' l) H Helium He atomic no.. '0 Lithium a10mic no.: : The arrangement of electrons in the first twenty elements .. 3 Li I 2.5 P Sulphur atomiC no. 15 . 2 2. 1 2.2 Magnesium atomic no.. eight electrons In the second shell and lhree electrons In the th'~rd shell..'-V\ Ar Argon atomic no.1 N Sodium atomic no.3 2. 7 2.: ~ . 11 \.0 -< >- 0 0 1 2 .2 2.. 5 2. Be BeryJlium atomic no. Hydrogen atomic no.6 2. 8. n. 16 S Chlorine atomic no. 19 K Calcium . (@) (@)(@)@J@» (/) u c Carbon atomic no.c . 4 Potassium atomic no.8.8. 20 Ca The numbers under each atom show the way the electrons are orranged for that element.1tomic no. 9 F atomic no. 14 j Si Phosphorus atomic no. This means it has two electrons in the first shell. 17 2. 1 2.. 18 2. 2 <11 1J . 8. 7 l) >- Ne Neon (@ ~ (@). This is called its electronic connguratlon.U N' Nitrogen atomic no. 6 N · Oxygen · atomic no. 4 2...4 Silicon atomic no. 7 atomic no. 13 AI 2. 0. 8 . 3. o. .Lon be.. X X.c.wn . Fathy Abdel Galil) Chemical Bonding Ions and Ionic Bonds An ionic bond is formed when one or more electrons is transferred from an atom of a metal to an atom of a non-metal..q e.on..Vto..c...d a.J.. U be.:t!ton....teJL.o ga.J...toge:theJL b!f a. ne.(. .8.<.J.8.·(NaCl) Na .l.Ma.wn a:tom lw.. de.c.'-!f chM..e.on.n oppa.de.!_e.17+ • 180verall charge • -1 chloride ion {CI-) sodium ion {Na•) Be..a!Ue :the· ...1) Sodium atom (2.tJt..ome.n be Jr. · po<.wn c.e...d ...n :the.(ion) 2' 8' 8 11 protons • 11 + electrons u 1 aOverall charge = + 1 10 17 protons 18 electrons . Ionic compounds are made up of ions.nd be..nc.the c.ome.e.tJwn.e.od.aLU e.Uve. a. ca.wn ch'-oJt.ga..22 Chemistry IGCSE (Dr.hM.c.. Ion : is an electrically charged particle formed from an atom by the loss or gain of one or more electrons. (2.. 7) (2. one.U) i.<.ge a.ve.:t. va. Sodium chloride .Uve.ge.ga.8. ofJ IJodJ.. a. a.de.tive.te.Lon.8) Chlorine atom Sodium ion (2. . .c..o LoU:.men.n e.L..c.d one de.!_e. c. o 6 :the ou. 6oUow.. ne.t<.. compound . ne.h'-oJt.. J. 8) Chloride ion .t o6 .he.e... .on. e.ne. SodJ.l.c.tvJe. ma.t<.ta.ga..t.. .. a..the.+ (atom) Cl (a tom) 2' 8' 7 2' 8' 1 sodium atom 1 chlorine atom {Na) {q) + Cl.t ga. held .nge.n.Lon. a.. e!_ecVwn.de.odJ. Be..c.o!Uc. a:tom lw.Ue. a.f. [.c.c.<.<.hloJt...:Ow.Lon •.de.h'-o!Une.nd c.l. The.n.pl(. the melting point of pure sodium chlonde rs 8 0 .2) (2. giving strong interionic forces.8. 8) 2 Fluorine Ma·gnesium atoms ·. sodium chloride lattice: 0 Cl ~~~ .8. ion (2. 8) 2 Fluoride ions Giant Ionic Structure: [Giant Ionic lattice] This is a regular arrangement of alternating +ve and -ve ions . 7) [Mg] 2+ <:x ~ ~F~ (2. They[' conducfrt t electricity when melted or dissolved in water. wns are ee o move and carry the electric current]. Fathy Abdel Galil) Chemistry IGCSE Magn.. ions held together by an electrostatic attraction between oppositely charged ions This explains the high melting points of ionic compounds.el>-Wm oxide (Mg 0) XX Mg·:~o~ ~ -xx (2.++. 2 . They are s. e.2) ~ Magnesium atom (2.8) (2. They are usually soluble in water.23 - (Dr. in other words.+ Properties Of Ionic Compounds: 0 1. .6) .g.g. 7) (2. Solid compounds do not conduct electricity.olids and have high m~Iting poi~ts ~nd b~gng points.in ionic crystals. (2. e. 3.8) x)( K FX ~(·' Mg: + ~ (2. - 24 - Chemistry IGCSE (Dr. Fathy Abdel Galil) Molecules and Covalent Bonds A single covalent bond is formed when a pair of electrons is shared between two atoms (non-metals). Covalent compounds are made up of molecules. H- H Hydrogen (Hzl a hydrogen molecule, H2 two hydrogen atoms a· shared pair of electrons Cl two chlorine atoms - Cl a chlorine molecule, Cl 2 88 Similarly, . Br2' 12, Fz Hydrogen chloride (HCI) XX H-0-H 0 H- Cl xx H \ Similarly, PC1 3 / N I H H - 25 - Chemistry IGCSE (Dr. Fathy Abdel Galil) · H I H-C-H - I H )> Draw a d.iagram which shows the arrangement of valency electrons iJ;I tetrachloromethane [CC4J • H I H-C-0-H Methanol ( CH 0H) 3 I H A double covalent bond is formed when two pairs of electrons are shared between two·atoms. 0=0 Oxygen (0 2 ) Carbon dioxide ( C0 ) 2 O=C=O H Ethene (C H ) 2 ~ \ / c=c I \ H Chemistry lGCSE - 26 - (Dr. Fathy Abdel Galil) A triple covalent bond is formed when three pairs of electrons are sha:red~ N Ethyne [Acetylene} N H-C==C-H c2 Hz PMpeJ!.tieb a6 Caval.en.t CampoWJ.cU [simple molecular] 1. Made up of molecules and contains no ions 2. Do not conduct electricity 3. Most covalent compounds are gasesandliquids,fewareso[ids. 4. Covalent compounds are less soluble in water than ionic compo.unds ·• 5. Usually have lower melting points and boiling points than ionic compounds. Diatomic Molecules The molecule consists of 2 atoms such as H , 2 o2 , N21 Cl , Br , 2 2 rz, Fz. Allotropes of Carbon Carbon occuts in tw0 solid forms, diamond and graphite. These are very different, even though they both contain carbon atoms. Pure diamond is a l1ard, colourless solid, that sparkles in the light, while graphite is a dark grey greasy solid with a dull shine, When an element has more ·than one form, it shows allotropy. The different forms are called allotropes of carbon. Allotropes: Different structures of the same element It cannot conduct electricity because there are no ions or free electrons in it to carry charge.(_el. joi. This because each atom is held·in place by four strong bonds.u. the hardest substance known. c V-UJ. by wea.n· pa.27 - (Dr. giant structure o[ caJtbon a. Fathy Abdel Galil) Macromolecular (Giant) Structure Diamond .JrJul. a. Ea.n hex. a. 2.thur..to111<1 aJte aiWl:nge..d J.to111<1.tom~ .lay eM.1i a. .a. :t~hedJw. Graphite I 1-weak forces CaJtbon a. .k 6oJtc.gonb J.U.ch caJtbon a. Diamond has these properties : 1. aNtangemen. the centre atom forms lour bonds .ned :to 6oUJt o. It is yery hard.d :toge..t.layeM ctl!-e hel.theJt.Chemistr:y IGCSE . This is vhy diamond is used in drilling and cutting.£.l.mond . The .tom ).]. ..:t o6 g.y IU.e. ThM be.. High m. carrying charge. (Silicon Dioxide} Silicon dioxide (Si0 ) has a giant 2 structure in which each silicon atom is bonded to four oxygen atoms and each oxygen atom to two silicon atoms. It is soft: and slippery vhich feels greasy.c. This is why graphite is used as a lubricant..gh me.n.28 - Chemistry IGCSE (Dr~ Fathy Abdel Ga!il) Graphite has these properties : 1.de .t¢. veJr. have.w..6e. o6 a.i.nd gJta. Ita<> a.:tom4.tti.I.n. This is because each atom has four electrons.p.Ue.:t e.i.i. Silicon (IV) Oxide }J.ox. Insoluble in wat~r .t <>bw.u. It is good conductor of electricity. luvuf.e...Uy.amond. ·. 2.c. and b.U.covalent structure of diamond.twr.i.tJr.lc.ke d.a.p. Hard [graphite is exception which is soft 1 3... Do not conduct electricity [graphite is exception 1 4.amond a.ng po. The fourth electron is free to move through the graphite.ph. properties ofMacromolecules: 1.ond!Le.la. This is because the layers can easily-slid over each other.nd dau no-t c. Bo-th d. bo-th eoitOJJ. IU. u. 2..:t a.te. <>ilieon d. This structure is similar to the giant .gh meLUng po. but forms only three bonds. Summary of Bonding Ionic (be-tween metals and no~-metals) Bonding 1'------ 1 Structures Giant ionic I I Melting point Conduct electricity ? Examples Covalent (between non-metals) .lectrons. Fa thy Abdel Galil) -29- Metallic Bond Giant metallic lattice . . C}L. graphite. NH3. Diamond Fe. Cu. · . Dr.. NaCI.. w~aker as in sodium and potassium (group I). the current is· carried by the free t.(In metals) + nucleus 0 electron Giant metallic lattice consisting of the positive ions surrounded by. a "sea" of free (mobile) electrons (i. H20 ~-J: >~ Water I f Giant metallic 1 . but they do when m:o!ten ! or dissolved in water I I (when i'ons are free I I to move) :' 7 / \. >·Metals are good ·conductors for electricity. > Metallic bonding is very strong in some metals like iron and copper (transition elements) and is much. CaC1 2 Metallic (in metals) diamond.electrons) ®8CB8® ~~®~ ®8+8+ I Ch. MgO. T~ Simple molecular I · Giant-covalent · '(macromolecular) Low· 'No ' Very high Usually high No Yes (has free . . h. Mg ~ ( i·rr ·XX . Si0 2 I ~I !. the etectrons ofthe outer shells). C02.C ~ ~~~ "v~ v'l.Chemistry IGCSE· (Prof. High Not when solid.e. Valency or Combining Power The valency of an element is the .... ~ Bromine ..c. Complete 'the follow·ing table Symbol Va1. ... Equations and Calculations] . (Dr.. Fathy Abdel Galil) STIOCHIOMETRY [Formulae. IGCSE Topic 4.......t What are the formulae· of the follwing molecules ·: Ammonia Methane Hydrogen chlorid. Fol!mula.enc'y Carbon c 4 Nitrogen N Oxygen 0 Sulphur..LLte!> Electron diagram~ ( 1 do·t and cross 1 type diagrams) or just a knowledge of the number of shared electrons in the outer shell can be used to work our formulae.... s Hydrogen 'H Chlorine Cl Bromine Br Ee..30 - Chemistry.en. of covalent bonds which the atoms can form.e.le..numper which shows its ability to combine with other elements.. Valency can be used to predict the formulae of' compounds.t Mo....... ...e .. ..emen. 1) The. In molecules (covalent compounds) it gives the number. o 6 Cova1. In ionic compounds the valency gives the charge on the ions of the element..... FolUnu. co 3 2.Here is a lis't of· most of the ions that you are likely to meet and will need to know : Valency I 2 3 Positive ions Negative ions H+.. The whole group-of atoms has two nega.a... These atoms are ··called ions·. o o 1on..c Compound& We cannot talk about molecule!! of·ionic compounds..nitrate ion • calcium ion magnesium ion ·barium ion iead. col2. More about ions : ----------------Some elements can lose or gain electrons and change into atoms with positive.e. 2+ Mg.31 - .ave as ions.· 2) The. Fathy Abdel Galil) . Zn2+ Fea· hydrogen ion lithium ion sodium ion potassium ion silver lqn ammonium ion • hydroxide ion • chlo'ride ior.oge'ther.+ Ca 2+ " . bromide ion iodide ion F._.C.phosphate ion • . Bal+ Pb2+ Cu-7~.carbonate ion • PO/. are other examples • 4 . the carbonate ion.. SO 2- is made of one sulphur atom 4 and four oxygen atoms.. NH +. Some examples are : Na+ Ca 2+ Cl. The sulphate ion. groups of atoms can have charges too~ and beh. The nitrate ion. No 3 ._. negative ·ions. In ionic crystals we have an alternating arrangement of p_ositive and . or negative charges. bonded· t. ion Spmetimes. sodium ion )(+ potassium ion calcium ion A13+ aluminium ion 02- oxide ion· . cnlorid~.Chemistry IGCSE (Dr.tive charges.ion copper(II) ion zinc ion irori(II) ion S2~ FeH Al 3+ iron(III) ion aluminium ion oHcrBrI- o2- so/- sulphide ion oxide ion· ·sulphate ion .fluoride ion Nol. and the ammonium ion.i... . u+ Na+ K+ Ag+ NH 4. ...... . sodium sulphate 5: copper (II) sulphate 6... Look at these examples in which the.12-l_ Mg ~ Mg~0 2 ...... The number of + charg. 1Liron (JII)....... ... Knowing this....... ~ 14~ potassiUI\1 carbonate 15....... ... ... aluminium hydroxide ........ alllrniniurn carbonate 8... 16. calcium hydroxide 12. ... ·........ . zinc chloride 4.MgO Remember i) Compounds ending in 1 ide 1 are made of just 2 elements only.. .. ·ammonium sulphate aluminium oxide magnesium oxide· this is then written &l ........ ............ -.... ... ii) Compounds ending in 'ate' have a third element......... . ·th ions are attracted to each other - by their opposite charges.. amrnonium.(Dr..:..... .... .. pctassium iodide 9 Cll!ciurn oxide . .....··. the formulae of ionic compounds can be written down........ 11..... 17... .... .... ....... .....numbers of positive ions· and negative ions are balanced to make the charges· the same...... 10... ......carbOnate .32 - Chemlstr)' IGCSE Predicting the formula of ionic corr Jounds In an ionic cempound........ sodium chloride 2.... .....es is alYays equal to the number of -charges..... 18.. .. ......... Question: Write down the formula for each ofthese ionic compounds: 1... .. zirlc carbonate 7.. 'oxygen'............. Fa thy Abdel Ga!il} ... ammonium phosphate . . silver nitrate . aluminium nitrate 3....... .. iron (JII) chloride .oxide... zinc sulphide .. <> motec..:tlra.htoJU.ol1. Example l. Make b~e you do no~ change any 6okmulae. When hydrogen burns in oxygen or air.U.:t CL 2 Example 2. Fathy Abde! Galli) Chemistry IGCSE .. n. hydMgenJ and ~lie MlogeM Me dULtom.6 ct . Make sure the· all correct~ formulae are· 3- th~ Check that the equation is balanced. oxygen..ex.:t .ne . it forms water + oxygen H2 + 02 2 H + 02 hydrogen 2 water > 2 H H 2 2 o o ~V!!g111~0 :tha. and· c.they . T/UU.the c. They form new chemicals called the products.(Dr.ul. it forms magnesium oxide [white powder}: magnesium + Mg + 2Mg + Ol)'gen ---7 magnesium oxide 2Mg0 .:t a.33 - When a che'mical reaction occurs.Ultogen. oxygen .t .c..eb c. These reacting substances are called tne reactants.:ta-i.i.o. Th. n. z~ Now write the equation using symbols. for each atom in turn.<>eb (n.ng wo <Uomb. IVfaoonesium burns brightly in oxygen or air.i.U.ommon ga.. mean.JU. How to write the equation for a reaction These are the steps to follow when writing an equation l- Write the equation in words (word equation).b ..i.6 02.o.:t 0. substances react together. . ........ . . . -.......34..>- + .. .. .. NO + Oz -----'?.. .. .. HzO + 2 Complete the word equation for the above reaction : .... a gas (g).. ....... .. KC! Mg + SOz + C!!t + 2..••• Na C! + c + COz -----'?. or dissolved in water (aq).•.. .. .••• N..... • Alz O.- Chemistry IGCSE (Dr.. ... .. -----'?-. Fathy Abde! Galil) Some chemical equations include extra symbols after the formula. A!CI..... . 0z + . .. ... ... liquid (1). + Hz(g) 1. .. COz + Ca(OH) + . + ---'.. . water . • • • • • • • • • • • • ..... Balance the fo!lowing equations : + Na C[z -----'?... ...... .. .••• CO A1 + Clz -----'?..... [aqueous] sodium + water sodium hydroxide + hydrogen 2Na(~ + 2H 2 0(1) 2NaOH(aq)... .. + • • • • ..Oz AI + Oz -----'?.. . They show if the surrstance is a solid (s). .... . . . .. 3.5 relative molecular mass 2 Calcium chloride.[Dr. NaC! 1 X 23 1 atom of Na 1 atom of Cl 1 X 35. CaC1 2 I X 40 I atom ofCa 2 X 35. The relative molecular mass (formula mass) of a compound is founq by adding up the relative atomic masses of the elements in the compound according to the number of each element's atoms.65 28 96 189 + + Calculate the relative molecular masses of the following compounds : l. Carbon dio:cide.5 40 7I 111 + . co 2 Sodium carbonate.35 - Chemistry IGCSE Chemical Calculations Relative Molecular Mass [Mrl Each element has its own relative atomic mass [Ar ]. Compounds have a relative molecular mass (sometimes called formula mass). Look at these examples: 1 Sodium chloride. Na C0 2 3 .a standard atom of carbon.5 2 atoms of Cl relative molecular mass 3 Zinc nitrate. This is the average mass of its isotopes compared with the mass of. Zn(N0 3)z 1 atom of Zn 1 X 65 2 atoms of N 2 X 14 2 X 3 X 16 6 atoms of 0 relative molecular mass - - - - 23 35. l~c.5 58. Fathy 'Abdel Cali!) . The % of an element by Ar of the element x no. of its atoms mass a compound in Mr of the compound Look at these examples: 1 The % mass of calcium in calcium carbonate.Chemistry IGCSE (Dr. phosphorus and potassium they contain on the outside.36 - Percentage Composition by Mass Sometimes it is important to know the exact composition of a compound. CaC0 3" Ca 40 100 = 40 + 12 + 48. For example. Fathy Abdel Gali!) . = 35% X 100 . all bags of fertilizer must show the percentage of the clements nitrogen. 2 The % mass of nitrogen in ammonium nitrate. X IOO = C~ + C + 3XO X = 40 % 40% of the mass of calcium carbonate is calcium.N0 3 2X N 28 = X 100 = ZXN + 4XH + 3XO 28 + 4 + 48 X 100 ---==--- 35 % of the mass of ammonium niuate is nitrogen. NH. ........ .... ,, .. ~ . . (Dr. Fathy Abdel Galil) - 37- Chemistry !GCSE THE MOLE A mo.e.e. (mo.tM. ma.o.6 r o6 any .6Ub.6.ta.nc.e. )_;, w Jr.e- .f.a.:Uve a.tom.Lc. ma.o.6 [Air.) OJt Jtel.a.tive. mo.tec.u..ta.lr. ma.6.6 [MltJ {.<.6 i l .i..6 a. compound) mea.oUJte.d .<.n glUJJn!>. For Elements : 1. 1 mole of· sulphur • the relative atomic mass in grams • 32 g .2. 1 mole of calcium = the relative atomic mass in grams = 40 g For Compounds 1. 1 mole of water = the relative molecular mass of water in grams =2XH+O - 2 + 16 2. 1 mole of Caco 3 - 18 g • Ca + C + 3 X 0 = 40 + 12 +'48 = 100 g mass No. of Ar moles Mr or Questions: 1. What is the mass of one mole of each of the following: a) magnesium Mg .................... . b) copper(II) oxide CuO· .............. · · · c) sodium chloride NaCl ............... . .·-·-·. ·.---.· . ·-·-·. - 38 - Chemistry !GCSE (Dr. Fathy Abdel Cali!) 2. What is the mass of a) 0.1 mole of carbon dioxide (C02)? .......... · - · · · · b) 4 moles of oxygen (02 ) ? ................ - · · · · · · c) 2 moles of water (H20)? ....... · ... · · · · · · · · · · · · · · · · · · · · 3. How many moles are there in: a) 9 g of water (HzO)? ........ · .. · · · · · · · · · · · · · · · · b) 1.6 g of copper (II) oxide (CuO) ? ............ - - · . c) 117 g.qf sodium chloride (NaCI)? .. : ............ . d) 9.8 g of sulphuric aci-d (HzS04 ) ? .... - .. · · · · · · · · · · e) 20 g of sodium hydroxide (NaOH) ? ............. - . Avogadro constant [ LJ .•• is the number of part~cles (atoms, molEcules) per mole of any subs tan.ce • The v:alue of the constant is A mole of iron (56 g) contains 6 X 10 A mole of A mole of A mole of A mole of A mole of A mole of 23 iron atoms. 23 carbon (12 g) contains 6 X 10 carbon atoms. ~ 23 sulphur (32 g) tontains 6 X 10 sulphur atoms. 23 oxygen atoms (16 g) contains 6 X 10 oxygen atoms. . 23 oxygen mole~ules (32 g) contains 6 X 10 oxygen molecules. 23 carbon dioxide (44 g) contains 6 X 10 carbon dioxide molecules. 23 .. water (18 g) contains 6 X 10 water molecules. ' " ' .' ..... ·•·. --.··.· (Dr. Fathy Abdel Galil) - 39 - Chemistry IGCSE Moles and chemical equations Not only do equations tell you what substances are reacting and being formed in a chemical reaction, but they tell you the amounts of the substances reacting. The equation·shows how many moles of each substance are reactipg. Example I . magnesiUm + hydrochloric .·magnesium _...,.. chloride acid +h d y regen Mg(s) + 2HCI(aq) MgCiz(aq). + H2(g) this means 1 mole + 2 moles 1 mole + 1 mole and in grams 24g + 73 g 95 g + 2g - the total mass on the left-hand side of the equation is equal to the total mass on the right-hand side of the equation. Equations can be used to predict the amount of a substanc,e that will be used up or made in a ch~mical reaction. Look at the examples: Example2, Consider the reaction between magnesium and oxygen. magnesmm 2Mg (s) + oxygen + 02 (g) -7 magnesium oxide . 2Mg0 (s) This shows that 2 moles of magnesium react with l mole of oxygen to give 2 moles of magnesium oxide. Using the ideas of moles and masses we can use this information to calculate the quantities of the different chemicals involved. 2Mg (s) 2 moles 2x24 =48g + + 2Mg0 (s) 1 mole lx (16x2) =32g 2 moles 2x (24+16) =80crh : ... Pick out the substances involved in the question CaC03 (s) 7 CaO (s) molar ratio: 1 mole 1 mole mass • The number of moles of CaC0 3 reacted 5 = - = • The number of moles ofCaO formed= 0.8 g = X 56 .· .05 • Mass of CaO formed = 0. Fathy Abdel Galil) 40 Example 3 Lime (calcium oxide) is formed by strongly heating limestone (calcium carbonate) until it is completely decomposed...:05 =2.. .05 100 Mr why? = number of moles x Mr 0 o.Chemistry IGCSE (Dr. The equation for the process is: CaC03 (s) CaO (s) 1 mole I mole =IOOg • 1 mole 40 + 16 =56g [40 + 12 + (3x16)] )> + 12 + (2x16) =44g Calculate the mass of calcium oxide formed when 5 g of calcium carbonate are strongly heated. ·. .. .. Using the information in example 3........ - X 100 theoretical yield (calculated) Example: On heating 5 g of calcium carbonate. not all of the reactants are converted to products.. The amount of product that would be formed if the reaction goes to completion is known as the theoretical yield. .. 2Na + S -7 NazS An 11. The amount of product formed in a non-complete reaction is known as the actual yield of the reaction. 41 Chemistry IGCSE (Dr. = ...... g (iii) Mass of sulphur reacted (iv) Mass of sulphur left unreacted == ...1 g of calcium oxide are formed.. what is the percentage yield of the reaction? >. actual yield (given) percentage yield ...e....... 2.... All of the sodium reacted but there was an excess of sulphur... [2 moles of Na react with 1 mole of SJ (ii) Number of moles of sulphur atoms that reacted = ........ ·........... g [4] .... Fathy Abdel Galil) Percentage Yield Some reactions do not go to completion......Sodium reacts with sulphur to form sodium sulphide.· ·:· .. i...... (i) Number of moles of sodium atoms reacted = .... ....5 g sample of sodium is reacted with 10 g of sulphur. Calculate the mass of sulphur left unreacted.... .t... g [1] (v) Percentage purity of the barium carbonate . is 24 dm 3 • (i) The number of moles of C0 2 collected ... in a volume of7.t.120dm 3 . NH3.........·.. This is known as the molar gas volume.·.. This makes it easy to convert moles of gas to volumes... g [ 1) (iv) Mass of barium carbonate . Insert the two · · missing volumes...p. ·...l> · An excess of hydrochloric ·acid was added to 1..... • Calculate the number of moles a[ ammonia gas.. Fathy Abdel Galil) Molar Gas Volume The volume of one mole of any gas is 24 dm 3 (litres) at room temperature and pressure (r........ BaC0 3 + 2HCl ---i- Baetz + C0 2 + H2 0 Molar gas volume at r..... Volume of gas (dml) No.'/ Chemistry IGCSE 42 (Dr......). [1) (ii) The number of moles of BaC0 3 reacted .._ then: The ratio of volumes =the ratio of moles • The equaiion for the complete combustion of propane is given below... The volume of carbon dioxide collected at r...p. Calculate the percentage purity of the barium carbonate...... and volumes to moles.... [ 1) percentage purity = mass of pure substance mass of Impure substance X 1oo ..2 dm of the gas _...... of moles (of gas) 24 dm 3 If the reaction involves only gases....... was 0.p. The impurities did not reactwith the acid..23 g of impure barium carbonate...t...t...measured at r....... volume of gas/cm 3 1o· ....p........ This rule applies to all gases... [1) (iii) Mass of one mole of BaC0 3 . . What is the concentrations of a solutio~ which contains 0. .. ... . the concentration of a solution prepared by dissolving 58. .. ... )> No.1 mole of solute in 102 cm of solution? ... . .. .. 25. .. .. . ..... UOH + HCt ---+ UC[ + H2 0 Number of moles of UOH in 25 cm 3 of a i . . .85 g (i. Concentration of HCL = .. = . .0 crrf3 of the acid. Fathy Abdel Galil) 43 Concentration of solutions The term concentration means the mass of solute dissolved in a certain volume of the solvent. .... .... . --·----~--- . methyl orange. Hydrochloric acid was added from a burette until the mixture just turned red... . ...0 emS of a solution of lithium hydroxide.... 2 moles). .. . . ...5 g (i.... . . . . . . .... ..... . . . . . 20.... ... . [0.. . (mol I dml) Volume · tdm 3 J Questions: 3 1.... ...1 mol I dm sulphuric acid (H2S04)? .00 mol/dm3 solution .0025 moles I 2. . . . The· number of moles solute in any volume ofsolution can be calculated: Cone. . .... . . How many moles are present in 25 cm3 of 0... . .. of moles Knowing the concentration . Calculate the concentration of the h)'drochloric acid.. . ... the concentration is 0... ... .... ....... . ·· [1 mol I dm I 3 )>. .1 mol I dm3 • Remember that 1 dm3 = I litre = 1000 cm3 ... . The concentration of solutions is expressed in g I dm 3 or mol I dm 3• For example.... . 0... ....... . 00 mo!ldrrf3 was placed in a beaker... . was needed to neutralise the alkali. ... Chemistry IGCSE (Dr.. .e. . . .. ... were added and the mixture turned yellow.. .... concentration 1.. ....1 mole)...e... .. .. the concentration is 2 mol I dm3• On dissolving 5... . ..5 g ofNaCl (1 mole) in 3 water to give a total volume of 1 dm3 is 1 mol I dm • On dissolving 2 x 58. mol/dm 3 [4] . Therefore number of moles of HCt in 20 cm 3 = . A few drops of the indicator. .. . a. compound ethane Ethanoic acid !fiOlecularformula empirical formula .: Molecular formula must be twice ·empirical formula. 80 20 1.<.c.-i..67 ·2o 6. u. C2H402 .v.the.67 : 3 CH3 12 + 3 15 } M..[Dr.67 20 to get the ratio: empirical formula (simplest ratio): Find mass of empirical formula: ·Compare with M. mew. CH3 CH20 _ICH3C02Hl methane CH4 CH4 Finding the empirical and molecular formula: Example: A hydrocarbon was found to contain 80% carbon and 20% hydrogen by mass. Its relative molecular mass was 30. is twice mass of 30 empirical formula . biJ . Symbols: c H % 80 20 . 0.. Divide by the sma!ler number 12 6. Find the empirical formula and the molecular formula. 2.67 6. Fathy Abdel Galil) -44- Chemistry IGCSE Empirical Formula and Molecular Formula The empirical (ormula of a compound shows the simplest ratio of the number of atoms of the different elements in it.to mJ.de. C2H. while its molecular formula shows the actual number of atoms of the different elements in it. molecular formula ts: 6. ... ....... Fathy Abdel Cali!) . ·············· .. ······························································· . of oxalic acid is 90 and ifs composition by mass is: carbon= 26. ······-····· ··········· .....[2] ....1% Calculate the empirical formula of oxalic acid..... The M............__ ..... -··· ................... ·······-...4-5- Questions __: c:::•--............................7% (i) hydrogen =2.......... 1. ·-·····......"" ............. -· ........................................... : ............. Chemistry IGCSE (Dr........_.............. mass Is 78.............................. What Is its molecular formula? ......2% oxygen= 71..................................._...................... [3] (ii) What is the molecular formula of the acid? ·················································································-~·:········································-[1] 2.................... '•• .................... The hydrocarbon benzene has an empirical formula CH and Its relative molecular....................... ....... ·...............· ..:c.........· .:.................................... t..·. of electrons in the o._ · . The horizontal raws are called periods and the vertical columns are called groups.-46- Chemistry IGCSE (Dr.te..{. arsenic. VI n Ll 0 V l!e 2 tundtlon ttit.. Sc Ti v Cr Mn Fe Co Nl Cu 5 Rb Sr y Zr Nh Mo .tallo. The clnsa of eiernents whi"ch lies on the borderline batween me!=als and non-metals is often classified as .utershell). Ill 1 en ""' ""' '' VI! 0 .ny bu.q.c.e a. c N 0 f' Ne AI Sl p s C! Ar Zn Gt Ge As Se Br Kr Ag Cd In Sn Sb Te I Xc "" Hg T! Pb Bl Po "' Rn._..>0 \ ~01. Fait examp. w Re Os lr Pt 7 f'r R2 Ac . THE PERIODIC TABLE The periodic table is obtained by arraneing the elements in order o£ increasing atomic number and piacing them in rnws so that similar elements fall into vertical columns..<.t~ ?J.too/u. 1. aJr. Fa thy Abde! Gal if) ·.-me.z Non ..ta..~• ~ ~------c--Melols---------1>- . IV H Metals take up tlte part of the periodic table to the left of the hefiVJ' line..t6 or me. {M l . ~oy. silicon.e .t belutve a. GrCKlp1 ·L 11.~>e!U.: '>j.{.----. ".t doe.o_em. . u. Elements of the same group have similar properties (the same no.oiU. q. me.'1 o. Be 3 N• Mg 4 K G. .o no.. .(. me..dh 1 e.. He H "_:It. Topic 5..t.ta..> - ~~ o-'0::: melols o· r 'a. . germanium.r 2.·.Uk.g. n.. Hf T. Ru Rh Pd 6 c.tlh "d _. :...o a.ta. The periodic table showing the division into ·metals and non-metals. in 2 dcctron~> to Group lll dementt have 3 dectroos to lose. to make :C{)I!. Group number 1 2 3 4 5 6 7 0 Valency 1 2 3 4 3 2 1 0 The reactivity of metals increases down a group Rb 5. I II u• Be 0 . > Li Metals react with non-metals to form ionic compounds.fill their outer Shell and form 1 ne&:uive ion..!I. ' .'• Fe1+ He III IV v VI VII B c N o'- p- Ne !Jl+ Si p s'. I Group '\_'II elements h1ve 1 electrons in their outer 'hells.-47- Chemistry IGCSE 3. in the: outer .of non-metals decreases down a group - '· > Br > I F > Cl 6. They (arm 3 ~ ions:.ompaund6. all h:ave l electron to lo$e from their outer shells..Cu2+ Znl+ I- Ag• Ba 2 + Pbl+ r -~ Group I elc:mcnt5..t. fUI their shell~. 4.0J11ic. Non-metals either join with other non-metals. then decreases.--- 0 N•• M~· K• c. or with metals to make . Group II dement' lll h:rve 2 electrons. They form 2'*' iOJ'lt.ions:. Group VI dements hne 6 elcciron11 in their outer s:hcl!s. They form + ions. (Dr.They need' to gi. > K > Na The reactivity. Relation between group number and number of valency electrons.· They need to gain one electron to. c.a- Ar Br- Kr . Fathy Abdel Galil) The valency (combining power) increases with_the group till eroup -4. They form 2.dlell. C:am)'JoWttll.te:n. ~ .to Sodillm c.Jr. Lithium.97 Sodium ion Na+ 64 0. Me.Oc..t c.ompouncU a6 GJr.t.n na. Fa thy Abdel Galil) Group I elements: the 'alkali metals' Density Melting point Name Symbol Lithium Sodium Potassium Rubidium Caesium Li Na 1.ommon GJr.Jr.the.e. The.tive.£{ Me...c.aup I compound.k: ~aLt·· de.aund '. Soft and shiny when cut Conduct electricity rodium.lt. MWLc.ta.<.tao Jr. ' I r The metals all have low densities.ta. NaC. Where are Group I metals found? The.t Me..are easily cut with a knife.90 Rubidium ion Rb+ Caesium ion cs+ They are called th!'...de.U o 6 NaC.a wa.wr..po.e. alkali metals because they react with water to form alkaline solutions. .a.Jr. The outermost shell contains one electron.te.tvu do na.53 29 1. Ve.53 98 Group lions Lithium ion u+ 0. The. Low density The metals are ail very good ciectrical conductors.86 Potassium ion K+ 39 !. . Lithium is the lightest metal known. The. sodium and potassium. 2. mo~. This is because tliey are less . me. Properties of Group I elements PhysiCal Properties The metals .dense than water.to ..thi!Jil!>e.oill.c.IJ many c..e.htoJr. K Rb Cs rc fgcm-J 180 0.-48- Chemistry IGCSE (Dr. all float on water. .· Metals further down the group are softer.{. : a) S e.aup I me.twr. · 6) GJr.t ac. .nd a.<.nd a. vr.c. :t:Jta U!J h 0 n wa:.tka.t<> .a.va.t.<.ten:Uy .tc.the wa.de when a.dded . Metals all burn easily in air e.e o 6 . Fa thy Abdel Gall!) -49- Chemistry l GCSE Chemical properties : very reactive metals Reaction with air: The metals are stored under oil. ga.te.mmedi.ort.tow..tha/: c.g: ssdium + 4Na(s) + 0 2 (g) potassium Reaction \vith water + OJeygen sodium oxide oxygen --->-potassium oxide Metals all react easily with cold water to form alkaline solutions.o. <>mill )!li.!> d . a.tM<. The heat from the reaction melts the metal as it reacts: sodium + water -+ sodium hydroxide + hydrogen 2Na(s) + 2H 2 0(!) -+ 2Na®H(aq) + Hz(g) potassium + water -+ potassium hyclraxide + hydrogen 2K(s) + 2H 2 8(!) --+ 2K@H(a<'J) + H2(g) The ob<.(Dr.<> a.. Z.ec.zzu 6a.{:eJt : 1.i.a.t.ty a.hu 6.OM . This is because they react with air. UthWm fi.tow a.U.<>. They quickly tf!rnish as they react with air.nd c. meW 1J. · The metals are only shiny when freshly cut. Po..tha/: d me.. meta.i.<> 6/-zze<> Mound d.um Jtea.. 3.0te.<> (i.Jr.W v.t i.the a. SocLWm 6.to a.a. ga.hoot<> a.n be ma.:t.O .tvr. o n..te... Reactivity of Group..n... least reactive of them. I metals heat Lithium The metals react easily to form chlorid"'>: Sodium Potassium lithium 2Li(s) + + chlorine Cl 2 (g) -+ -+ · lithium chloride 2LiCI(s) sodium 2Na(s) + + chlorine -+ Cl 2 (g) -+ sodiuni chloride 2NaCI(s) potassium 2K(s) + + chlorine Cl 2 (g) -+ Rubidium n Caesium potassium chloride -+ 2KCI(s) So you can see these Group· I metals have similar properties.o 1 e..-50- Chemistry !GCSE (Dr.l$j~ ~ _.mliaJI...he. M. .u.· Potassium is the most reactive of the three.. ha.~-CQ-". Group I compounds Metal Chloride Bromide Nitrate Sulphate Carbonate Lithium LiCI LiBr LiN0 3 Li 2 S0 4 Li2 C03 Sodium NaO NaBr NaN0 3 Na 2 S0 4 Na 2 C0 3 Potassium KC) KBr KN0 3 K2 S0 4 K2 C03 GJtoup r ~a. Why they.UJr.o:Ud~ I n.IL.. Lithium is said to be the.i.f. J ivte.b.. .U~ ? In the elements of Group I. That is why· the elements hehave"in a similar way.:>.C.<._ __.... ·FathY Abde! Cal ill Reaction with chlorine: metal ·~ chlorlne---->-gas \ · ~ 1"'~~'--~_.aJtbona.ve..Udo.Lt6 {c. ·~. Elements behave in a similar way if" their atoms have the same number of outer-shell electrons...n_.e. [giving a colourless solution] metals get more reactive .\.t~ I c. w!U. all the atoms have.Lc ~ o. pltopeJt.! electron in the outer shell..Jt._tofume cupboard .n wate.tc.te. because it reacts the most slowly".i. l a.51 - Transition Elements e.Chemistry IGCSE . V.d.tt.nd va. Fe.phy¢-i.is used in the m<i.~>.nd c. (aq).mi.a.· Typical characteristics of transitipn metals .catalysts a) Iron ·. strong). Fathy Abdel Galil) Cu. Cr. .e..tM. 1'-!i..uion Potassium me.e. b) V~nadium (V) oxide is used in the manufacture of sulphuric acid.t.t Hg) and densities (hard. 2 3 different charges. :. Compa:tr.c.. (Dr.um (gJtOap I me. are green. Fe +.. FP.wm (bw.g. .e. Co. They .eo bU:ween.na.form colou_red compounds.~re metals of high melting points (exceP.Cu iron (II) ions. 1. pa. They.B.a. i.ta.{.{.he.l. copper (II) ions. Vanadium . Host of them have more than one valency. 4.the.l p!topeJU. e. e. 2. Fe +.tall a.c. 2+ 2+ (aq) are blue.g.nufacture of ammonia. forming ions with The metals and their compounds can act as . This means ihat it easily turns into a gas.. + '=fry mcreaszng >-Bromine is very volatile [has low b. ·Halogen Molecule State at Colour room temperature · Pale yellow Symbol of Halide ion F - CI Fluorine Fz Gas Chlorine Cl 2 Gas Green Cl Bromine .ome.(Dr. a chlorine molecule.. Cl .. The tWo atoms in the molecule are joined by a covalent bond.. . F - - Br I . The halogens all exist as diatomic molecules. PVC (insulation for electric wires) .52- Chemistry IGCSE Group VII Non-Metals the Halogens D c.Cl .ey I Astatine At 2 . Cf2 Uses of Chlorine: • Making bleach .e.. >- Iodine is a dark grey solid.. .. daltkvc.. 59°C}. . bec. In water purification [kills bacteria] "' Maldn.. when warmed.oUJr.o.t. Fathy Abdel Ga!H) .Br2 Liquid Red-brown Br Iodine 12 Solid Dark gr.p. it turns into a purple vapour [it sublimes]- >- Aqueous solution of iodine is brown. Damp indicator paper is quicldy bleached with chloiine.a. mOJte Jtea.e a. -Test for Cl Displacement reactions: chlorine Cl 2 (g) 2 gas : Chlorine bleaches damp litmus paper..ogen w. leo<> Jtea.(aq) + potassium chloride 2KCl(aq) [red] Brz + zcr a. -+ [colourless]· ionic equation: -> + 2 Br· -> 7 iodine + I. Reaction with .l.brown] Iz zcr + bromine + Br. WOJtd.f.e. Clz 7 potassium -+ bromide 2KBr(aq). [colourless] Ionic equation: + Clz .indicators: -+ -+ sodium chloride 2NaCJ(s) Chlorine gas dissolves in wa\er to make a powerful bleach. the outer shell. chlorine + Cl 2 (g) + zr In o:thvr. Chlorine can displace bromine and iodine from a solution of their salts: chlorine gas-·===\\ v ~I>Otassium Iodide solution ·1oame belng forroed chlorine + Clz(g) + potassium -+ iodide 2KI(aq) __.metals: Halogens react wi~h.c:Uve ha... Fa thy Abdel Galil) ·:·: Chemical Properties . ..-53- Chemistry !GCSE (Dr. .c:Uve hai. Halogens have similar properties because their· atoms all have 7 electrons in..c..(aq) + potassium chloride 2KCI(aq) [. most metals to make salts: + + sodium 2Na(s) Reaction with.Ut dUp.ogen t)Jtom ffi compound. Argon.. it gives out a bright light and is used in lamps and advertisement signs. Neon. Helium is very light and.o. 2..-54- Chemistry I GCSE (Dr.ac.Uo/1. tung5ten filament 3. now hel. so it is used in ballons and air ships.inert atmosphere It is very unreactive and-helps protect the filamenc.Wm Mpl. does not burn. They do not usually form compounds and exist as isolated single atoms (i.e. He Uses of Nobel Gases 1. The nobel gases in group 0 are very unreactive (inert). they have complete outershell of electrons. argon Neon : When an electric current is passed through neon gas. Xenon 1..6. neon etomi"::\\\ ~((G N• hollum atocn• ·-<--__.Ut . Argon i~ for fil1~ng_electric light bulbs as an. .6.Uo/1. Fathy Abdel Gs!il) Nobel Gases : Helium. Krypton. HqdJtogen hqdJtogen WCL6 601t £L6ed .t in ba.the pa. monoatomic). Whq ? ••••••••••••••••••••••••v••••••••••••••••••••••••••••••••• .ed 6-UUng ba... ••• 2. Upward delivery For gases which are soluble in water and less dense than air such as NH .oUec. gas __._ gcw-jM .. Fathy Abdel Galli) Test for Gases Test Result Hydrogen Lighted splint Burns with a pop Oxygen Glowing splint Relight:s Carbon dioxide Limewater Turns milky Chlorine Colour Yellow-g'reen Damp litmus paper Bleached Ammonia Smell Pungent [ttlkq.wJtd deUveJty..c than Wr. 3 H [Ughte.) Mn be 2 a-Uo c. -l-i>' Upward delivery over water : For gases which are insoluble !n water such as H .-55- Chel)listry I GCSE (Dr. o2 and N2 • Downward delivery : For gases which are soluble in water and denser than air 3.ted bif up.Une gcw l Damp red litmus Turns blue Formula Gas paper Collection of Gases gas l. 2 2. 11uestion : ~-""""'""'""'""'-=-- W/Uch o6 . so 2 by pasa_ing it through concentrated sulphuric acid may be dried [dAy.nno.d )!.mmoiUa.t be. tt<1 rid be.-56- Chemistry IGCSE (Dr.c.phU)()_c a.e.d .angeme.UoW-Wg cuur.d a. co!LILe.ng agent]. e. r.=='d=r=y==~ concentrated sulphuric acid concentrated sulphuric acid 2. Gases that do not react with acids such as· co 2 . Fathy Abdel Galil) Drying of Gases 1. U 1r.aw wUh a. gaJ.n. w.~ng a.te. .W.c<.t f 2 1 ~===:.sul.[Conce.te.Uh concen:tJur. gaJ.cJ.d ca. Ammonia gas is dried by passing it over solid calcium oxide [drying agent] >.the.ca.] ammonia + sulphuric add -----+- nmmonlum sulphate . 6o..tl> 6oiL dJty.i./Lt!ta. mention the reducing and oxidising agents.n. So the reaction is called redox reaction. Reduction and oxidation always take place together in a reacticn. ----7 2Fe Common reducing agents hydrogen.0(g) 2 Re. 1 oxidised. the blnck powder turns pink~brown (copper) • .t The copper(II) oxide is losing oxygen. What is the purpose of the ice? reduced. reactions.. )> Reduction is defined as the removal of oxygen. reactive metals . The hydrogen is gaining oxygen.a. It is being reduced. Question: Which substance is oxidised and which is reduced in the following . carbon. It is being oxidised._ . + 3CC)z : carbon monoxide. I copper( II) oxide· + hydrogen + CuO(s) -7- copper + water Cu(s) · H (g) 2 + H ..ge. Fathy Abdel Galil) -57- Chemistry IGCSE Oxidation and Reduction copper(II) oxide excess hydrogen burning in air [black] ·ice water When hydrogen is passed over black copper(II) oxide in the apparatus above. In other words: > Oxidation is defined as the addition of oxygen.due-Utg .(Dr. n..e.on a. i. the addition of hydrogen is a reduction reaction.to oxyg e.gne. Jte.Ul.ud a.nd .wn I.f.. Fa thy Abdel Ga!i!) )> Since hydrogen is a common reducing agent.)..).the axyge.wn .n ).-58- Chemistry IGCSE (Dr.two el. Oxidising agents accept electrons.e.nd oude ion aM 6oJtmed.Jt.ecbw 111> a. oufued.c. removal of hydrogen is oxidation. w/U.h ).I. 2 e oz- + 2 e Ma.e.to~>e. Jte..f. and the opposite.duc.gne. it follows that: Reducing agents give electrons.ectltoJ1-6.ectJto111>.).til. Vwring . .1u el..g lteJ>. w/U.gne.a. In which change shown has nitrogen been reduced? B nitrogen.tw Jt.du. el.i.ed. .wn ). oudA.ch ). ga. N2 c ~----------~ N02 D )> Redox in terms of electron transfer [01 L] [RIG] Oxidation Red·uction Is Is Leiss of electrons Gain of electrons From the definitions above. oxygen.Med filtom ma.aiU 6e. . . Ma..ott.i..)..cvi.wn. Consider the reaction of magnesium with oxygen : magnesium + oxygen· --+ magnesium oxide 2 Mg + 02 ~ 2 MgO The ma. 0 + Mg 2+ Mg. Oxidation and Reduction [summary] with respect to: O!fgen hydrogen electrons oxidation state oxidation addition of oxygen removal of hydrogen I loss of electrons [OILJ .·acidified potassium magnate (yii) solution : The colour changes from purple to colourless.g. The oxidation state of chromium in chromium(III) oxide is 3 and in potassium dichromate(VI) is 6. decrease in oxidation state - Tests for oxidising and reducing agents a) Oxidising agent (oxidant) + potassium iodide solution The colour changes from colourless to brown [h]. b) i. e. Reducing agent (reductant) +. increase in oxidation state· reduction removal of oXygen addition of hydrogen gain of electrons [RIG] . )> Reduction involves a decrease in oxidation state. Change in oxidation state )> Oxidation involves an increase in oxidation state. Reducing agent (reductant) + acidified potassium dichromate (VI) solution : The colour changes from orange to green. .-59- Chemistry IGCSE [Dr. Fathy Abdel Galil] Oxidation States [Oxidation Numbers] The oxidation state of iron in iron(II) oxide is 2 and in iron(III) oxide is 3.g. The oxidation state of manganese in manganese(IV) oxide is 4 and in · ·potassium manganate(Vll) is -7. e. ii. Electrolytes and Non-Electrolytes : . they conduct weakly e. is non-metal. liquid under test ::' . plastic. Solid substances that allow electricity to flow through them nre called conductors. wood. Those that do not conduct are called non-electrolytes.-----1 F a battery A lamp. why ? Semi-Conductors.ctric cun:ent are called electrolytes. and-rubber ar~ insulators.g. one very important exception.. · . electrode called cathode 8 electrodes. Carbon. All non-metal aubatancea such as glass. Generally made of graphite or :::::::H-+--1 unreactive metal like platinum <±) electrode called anode . c. They are substances which contain no "free electrons" and no "ions" bu·t allow very small cunerit ~O··'pass through them. Liquids that conduct an ele. If it glows. . The following figure shows the apparatus that could be used to see if a liquid is an electrolyte . how- ever.60- Chemistry IGCSE Topic 6. (Dr.ctricity. pure water. in the form of graphHe. All metalo are good conductors of electricity.Wc. There is.:. but a very good conductor of ele. electricity must be flowing through the liquid. so they are ionic compounds that are molten or are dissolved in water. why. Covalent compounds such as ethanol. i. Fa thy Abdel Galil) ELECTRICITY AND CHEMISTRY [ELECTROCHEMISTRY] Conductors and Non-Conductor:.on.e.or sugar solution are non-electrolytes.. Substances that do not allow electricity to flow thr·ough them are called non-conductors or insulators. Electrolytes are substances that contain ions which are fi:ee to move about. )>- Can you suggest why -ve ions are called anions and +ve ions are called cations? ..J Non-electrolyte ethanol petrol sugar solution pure water .J ....... •••••••••••• 0 0 0 •••••• 0 •• 0 ••••••• 0 0 • 0 •••• 0 •••• ' ••••• 0 • 0 0 .. electron flow electron flow e cathode ·.J ....J molten salts . ....J .J oil . .. At the cathode...J solutions of salts· in water ... -ve :!:ons lose electrons and become atoms or molecules.... At the anode..lel Galil) Electrolyte solutions of acids and alkalis in water ... Chemical changes take place at the electrodes. :_·anode (£) ·negative ions lose electrons at tho"· anode electrolyte .. Fa thy Ab<.-61- Chemistry IGCSE Typ~: free moving wns )> of su~srtmce _ (Dr........ ':· During electrolysis... .. +ve ions gain electrons and become -atoms or molecules. . a battery r-~--t'I t------.J Electrolysis : Electrolysis is the decomposition [breakdown] of a substance by electricity. ions migrate towards the opposite electrodes........ ! . The electrons flow in the external circuit from the anode into the cathode...... / . .... :take place ... .~ Brz + 2e· > Complete the following table: molten electrolyte. .. ...... . .. . ..... ... . .. ....... magnesium fluoride aluminium oXIde Product at cathode lead .y} . ... . . .. .. .. .. .. . ... . .. · Product at anode bromine t- . . PbBr2 At the cathode Pbt+ + 2e. The rules for the .FathyAbdel Gali!) Electrolysis of Molten Substances using Carbon Electrodes The compounds are decomposed into their elements. electrode reactions are summarized as follows : Electrolyte Lead bromide. . . ... . electrolysis of molten compounds are : Molten Compound •:: At the anode + Non-metal At the cathode Metal > Electrolysis of molten lead bromide [PbBr2] + - a battery .. .5 a 6 moLten lead ·(gJte. . . ... lead bromide sodium chloride .......ap... - molten lead bromide t heat >:Explain..-62- Chemistry IGCSE (Dr....... .. . . .. . ......... . ..... ·. ......· carbon anode + carbon cathode - bubbles ~F brown gas {bromine) dlr... .... > The. .. .... ........ .... why the lead bromide needs to be melted for electrolysis to . .. . . ~··.... .....~ Pb At the anode + 2Br. ... / -~ 1r ' ~-. Electrolysis of Concentrated Aqueous Sodim Chloride :[Brine} : At cathode./ectrolysis of: (i) Molten sodium chloride (ii) Concentrated aqueous sodi!fm chloride )> ._ Electrolysis of Concentrated Uydrochloric Acid: · At the anode + At the cathode - Electrolyte .___ __.--J Only Cr takes part in electrolysis because it is present in much greater concentration than OH jz Cr{aq) -7 Cl2 (g)'+ 2 e· / This leaves a solution containing sodium and hydroxide ions (a solution of sodiwn hydroxide.-- --- I .-- ·... HCI (aq) 2 e. there is a cation (H") and a anion (OH) from the water. --" Only F takes part in electrolysis [H being lower in the reactivity ·series than Naj I2 F (aq) + 2 e· -7 H 2 (g) . Fathy Abdel Galil] .---. f -. NaOH).-7 H2 (g) 2Cr (aq) -7 Ch(g) + 2e··.\ __ d-.-63- Chemistry IGCSE [Dr. ~ -. FromNaCL -. Electrolysis of Aqueous Solutions: · The products of electrolysis of aqueous solutions are difficult to predict than molten compounds. ~ Atanode + .. The solution is alkaline (i. Compare the products of e.litmus paper blue).. LNa+ .oH_.-._ --.-. 2W (aq) + Hydrochloric acid... turns red .e.. This is because as well as there is a cation and a anion from the salt.·.+ ' . oxygen gas is produced .-64- Chemistry IGCSE [Dr.. .. Fathy Abdel Galil] Manufacture of Chlorine and Sodium Hydroxide : The method is based on the electrolysis of concentrated aqueous sodium chloride (brine)•... then hydrogen gas is produced If the metal is lower than hydrogen in the reactivity series.. The reactivity series Na Ca Mg AI Zn above hydrogen.·. brine chlorine lui~_____. then the metal is deposited (formeq}. . . so hydrogen gas is evolved at the cathode Fe Pb Cu Ag least reactive Au below hydrogen so metal deposited at the cathode )> )> At the anode + For concentrated solutions of chlorides. . ·•· ~ pos!Uve eleclrodo aqueous sodium hydroxide neg alive elec[rode Predicting the Products o[Electrolysis o[Aqueous Solutions : )> )> At the cathode If the metal is higher than hydrogen in the reactivity series....· chlorine gas is produced For sulphates and nitrates.·. -65- Chemistry IGCSE [Dr. )> The solution changes from blue to colourless I I 2) - cathode anode + I 0 . b~r.. inert) -{ Cu +) ... Fathy Abdel Galil] Electrolysis of Aqueous Copper(ll)sulphate : Using carbon electrodes (i. --· -· -· · 2 FromCuS04 Atanode + ~ Atcathode .IC. (II) . ' 0 c ' bubbles of oxygen 6Oc_ c.rr\-·-· FromHzO I / 10Ir' 'r ----- Onlythe copper ions take part in the electrolysis.....ul.I 4 \.fu:ti..pha. M.:tqueous copper-(II) sulphate: atcathode copper The solution left is dilute sulphur~ acid (H2 S04)./ 1- ..-..o n Summary: Electrolysis of :.oU 6 c... Only the OH ions take part in the electrolysis..-.own 0 de.:.IC.o ppe.1 . - 2.po.. ...----' • ..oppe.e. Cu 2+ (aq) + 2e· -7 Cu (s) Copper deposited on the cathode (as brown deposit) Oxygen gas is given off The solution left is dilute sulphuric acid (H2SO_J.te. atanode + oxygen .. --so . ..e. nickel. the anode dissolves) [anode: decreases in mass] [ Cu (s) ~ 2 Cu + (aq) + k J Copper deposited [cathode: increases in mass] I Cu2+ (aq) + 2e- ~ The aqueous copper(ii) sulphate remains unchanged.e... -7 Cu2+ -7 -7 Cu 2. zinc. Active electrodes: e. (i. They take part in the electrolysis and the active metal anode dissolves. Electrolysis of Aqueous Copper(II)sulphate : . Inert electrodes: Carbon (graphite) or platinum.g. In other words.- vaqueo us copper(II)sulpltate """~. silver. copper. Types of electrodes : . passes into solution as ions. Using copper electrodes (i.. I...e... ll ~ copp er caih ode - copper an·ode + 1. the mass of the active· metal anode decreases)...[Dr. active) . (blue) Atanode + Atcathode - Copper passes into solution as ions (i. Cu (s) I . Fathy Abdel Galil] -66- Chemistry IGCSE '•. They do not take part in the electrolysis. . Fathy Abdel Galil] -67- Chemistry IGCSE Application of Electrolysis: 1} Refining of Copper: Copper can be refined by electrolysis using a block of impure copper as the anode and thin sheet of the pure copper as the cathode.fll!.. The anode is made from .....> ·EB e an... )... CO(I(Il!.. .phai. cathode......on. The method is similar to that used to refine copper. Complete the following statements. Impurities sink to the bottom of the container as anode sludge.......out.. about refining of zinc.nickel · the anode will be made fro in copper silver nickel the electrolyte will be aqueous copper(II)sulphate aqueous silver_nitrate aqueous nickel sulphate . The electrolyte is aqueous copper(II)sulphate........ pU/tl!../t( I I )....... 2) Electroplating: Many metal objects are electroplated for: a) Protecting them from corrosion and rust b) Making them look attractive anode: _ _:::................... The overall result is the transfer of copper atoms from the impure copper to the cathode....uil.... I ... The electrolyte is aqueous .....{tion contairzing..ions of the plating metal if the object is to be plated with copper silver ..e...... ode....oot. .. Zinc can be refined by electrolysis.............. ..[Dr...- cathode: (object to be plated) (metal used to plate the• ::>bject) ·='='""='!-·electrolyte:- aqueous solr.... . The cathode is made from ./t cop. .> As the hot oxygen escc·."'l"""___ 1±/ Molten electrolyte -HI-(aluminium oxide fil!. Aluminium oxide has too high melting point to be used on its own. Al 20 3) is electrolysed in molten cryolite (Na3A1F6). extracted only by electrolysis. . .. The purified bauxite (aluminium oxide. cryolite is used to lower the m. .Chemistry IGCSE -68- [I?r... Extraction of Aluminium Ore: Bauxite.ofccll(cathodc) dissolved in cryolite) · At cathode- The aluminium sinks to the bottom. Carbon anodes (".pes. Fathy Abdel Galil] 3) Extraction of metals Reactive metals above Zn in the reactivity series such as Na..e. --~..p. ard so they have to be replaced from time to time.. so it dissolves in molten cryolite at 900°C (i. .. AI At anode + Oxygen gas is produced. 8.-l~·carbon lining .o. it burns away the graphite anode· ( C + 0 2 7 C0 2). Mg. ofAl1 0J) .> Making aluminium is an expensive process because large amounts of electricity are needed. Ca.). AI can be. o ul. In other w..te l H so 2 4 2H+ so 2 - [.(Dr. magnesium sulphate ___. ·common acids: strong Acid Formula Hydrochloric acid HCl Nitric acid HN0 Sul..FathyAbdel Galil) -69- Chemistry IGCSE Topic 7. Reaction of acids l. f:cids reac_t. It is the hydrogen ions that cause the change of colour. . II'" (aq).phur:Lc acid { weak <-.t!ta.~ (aq) + Hz (g) ionic equation: Mg (s) + 2H+ (aq) ------'Jr Mg+Z (aq) · + Hz (g) + -hydrogen . Aqueous solutions of acids tUrn the colour of litmus red. ACIDS.te J CH COOH 3 H+ CH COO 3 3 4 - [ e.:tJut.with reactive metals to give a sa·lt and hydrogen acid + metal salt '+ hydrogen dilute sulphUiic acid magne>lum ribbon magnesium Mg (s) + .p fta.te J- Basicity of acids: · Monobasic such as HCI. BASES AND SALTS Acids: An acid is a substance giving hydrogen ions. CH3COOH such as H2S04 Dibasic. Remember that the hydrogen ion is simply a proton. HN03 .Ethanoic acid (Ace tic acid) Ions present in the acid -- [ehto.ords. · MgSO.noa.sulphuric acid + H2SO. an acid is a proton donor.!UdeJ H+ Cl H+ NO..~ (aq) --r. [ JU. . . in aqueous solutions. . (aq) + ccpper(ll) --+- oxide + CuO(s) --+- b. 2 so 4 (aq) copper(ll) sulphate CuSO.(s) --+ calcium chloride CaCl 2 (aq) + water + + H 2 0(!) + carbon dioxide C0 2 (g) dilute hydrochloric acid 2HC!(aq) >- ' T --+ Thing to remember about hydrochloric acid: Hydrochloric acid is a solution of hydrogen chloride gas in water.(aq) + 2 NaOH(aq) ~ Na 2 + water + H2 0 (I) sodium sulphate + water so 4 (aq) + 2 H 0 (. Fathy Abde! Galil) Acids react with bases (metal oxides and hydroxides) to give a salt and water [neutralization] Acid + Salt Base· + Water dilute rulphuric acid ·:.fue Sulphuric acid + sodium hydroxide H 3.ck b. carbon dioxide and water ·acid + carbonate --+ salt + water + carbon dioxide + calcium carbonate CaCO.a. heat sulphuric acid H 2 SO.t. (Dr. water HCl (aq) HCl (g) [covalent] [ionic] •:':· .f) 2 Acids react with metal carbonates to form a salt..ro- Chemistry IGCSE 2. Ox.remain un-Ionized In the solution e.e of colour. hydrochloric acid sulphuric acid nitric acid we k Partially ionized In solution.crong { weak Formula Ions present in the alkali Sodium hydroxide NaOH Na+ '"'"'''= "''""""' KOH K+ Calcium hydroxide Ca(OH) NH (aq) or 3 NH 0H f-.i. ~ . and hydJr. molecules . 2. a proton acceptor.ely ionize in· water.g·.. a is formed. sodium hydroxide. complet. some of the .. If an alkali does not. This reaction is called neutralization reaction.. ethanoic acid citric acid [in citrus fruits] Similar-ly. An aiH. i.e·.tJwng alkatl is produced. hydroxide.e. 2 OH - 20H OH Ca 2 + NH+ OH 4 4 Solutions of alkali turn the colour of lit"mus £~~~It is the hydJr.a.g.k.deh of metals are bases. ~OM that cause the chang.ox. If a base is soluble in . Fathy Abdel Galil) Bases A base is a substance that can accept hydrogen ions.e. Properties of bases : 1.-71- Chem_istry JGCSE (Dr.g. e. e..g......_ if an alkali completely ionizes on dissolving in water. a . potassium . the solution is called an alkatl.. ·ammonium hydroxide (aqueous ammonia). the solution wi!! contain a high ·concentration of hydrogen ions. l .de...ater.i. we. calcium hydroxide.ater only (see properties of acids). Weak and strong acids and bases Acids strong Completely ionized in solution..i.ith acids to form a salt and . e... ·Bases react ..ox.ali is a base that is soluble in water - ' Common alkalis : ·Alka-li .Aqueous ammonia (often called ammonium hydroxide) 3. !.du. They are said to be Insoluble.. and ammonium salts All nitrates except Sliver and lead chloride Chlorides ••• except Calcium. Falhy Abdel Galil) -72~ Chemlstiy IGCSE nre pH scale The strength of an acid or an alkali Is shown using a scale of numbers called the pH scale. weak alkali. a.. potassium. Uke litmus. and ammonium carbonates ••• But all other carbonates are Insoluble .g.. potassium.l.. Soluhle Insoluble All sodium. On this scale : an acidic solution has a pH number less than 7 an alkalic solution has a pH number greater than 7 a neutral solution has a pH number of exactly 7 a The pH can be measured by using universal indicator..g.. MUiral..&Od!um hydro>:ida Salts A salt is a compound made from ari acid when a metal takes the place of the hydrogen in the acid The salt made depends on the acid : • Hydrochloric acid gives a chloride • Nitric acid gives a nitrate • Sulphuric acid gives a sulphate " Ethanoic acid gives ethanoate....!TliTlOllla The pH can be measured more accurately using pH meter. hydro- o.g.___ / e. barium and Sulphates .(Dr. Soluble and insoluble salts Some salts dtssolve·ln water easily. / o. Unlversallnd!cator Is a mixture of dyes.n ' ' - ' unlversal!ndlcator colours 1 pH numbers 2. it can be used as a solution or as universal Indicator paper. Other salts do not dtssolve at all..g. it goes a different colour at different pH value as shown In this diagram: yellow violet blue orange red .___ 2 . 3 5 4 .__ / / / / ~r~.. '-. They are said to be soluble.aq.. lead sulphate Sodluin. otha- chlol1c acid nolc acid 6 7 8 11\ g 10 11 12 13 14 -"""'<trona alkall.g.water e.. Excess zinc is added to dilute sulphuric acid in a beaker until the reaction stops fizzing and some zinc is left • The mixture is filtered.73- Making Soluble Salts 1. A metal. The solution formed is then evaporated.----e:Vaporating 'i basin zi:!:· Zinc sulphate-.... ~zinc sulphate solution /·. could also have been made using· zinc carbonate instead . 5.. Fathy Abdel Galil) . Separate the crystals by filtration and dry them between filter papers (or in a warm oven). but the gas given off would be carbon dioxide and not hydrogen.. . ..!..! method and apparatus would. zinc sulphate solution. Allow the solution to cool..would be given off and warming is necessary....... of zinc. The filtrate.. crystals of zinc sulphate are formed. a base or a carbonate can be added to a dilute acid. solution ~~2~. 4. No gas . dilute sulphuric... zinc oxide could have been used instead of zinc. What wil~ be left in the filter paper 7 .~. is evaporated in an evaporating basin to crystallizing point.····~······································'"···· 3. Similarly.. 1. be use<.-111/ acid "-=Cd=_.zinc sulphate / crystals of ... The ·sam>. 2. ' .Chemistry I GCSE (Dr.. t c.e. 5. (Dr.c).ci.. c. Cl.a.••• 4. using the same volume of alkali and the same volume of acid. 0. 6. Acid is run from the burette into the alkali.ocU. the salt solution is evaporated to the crystallising point. &oWtion bwr.c.pe. 3 drops of suitable indicator such as phenolphthalein (ph..towr. ~ l ph.Uu:te.i::Jr. allowed to cool . :the. but without indicator. When me:thyi. <..tou.olu. n.. 3.•.U 6Jtam yellow to red • u.•••••••.&! <.ph.!rl.JLt e.odW..o.wn /--'---\/ hyd. ) . Finally.o<> l.¢ eel C1.d .CI.tie.tie.•••••••.m rU.) are put into the alkali.:Uan Cl.74 - Chemistry IGCSE 2. phena.hCI.a OH (aq) 3 --> + d.ng e. 25 cm 3 of dilute sodium hydroxide is put into a conical flask with a pipette. c. Fathy Abde! Cali!) ..de.•••••••.U!Uc.tph:dut.hCI. the solution is' neutral. colour will it turn Z.e.6 p{.d.p. j w. 2. A burette is filled to the zero mark with dilute nitric acid. What. <.ng e.J.•. The experiment is now repeated.te.•. ph.a.ncU...c.{.Making sal!s from acids and alkalis [the titration method] Making sodium nitrate NaN0 HN0 (aq) 3 + N.ng e. '-----"Z. (M.nk :to c.6 i.JW x... 01r.:taJt. that has been added. When the indicator just changes colour (from pink to colourless). (aq) + Na 2 S0 4 (aq)-+ PbSO. sodium nitrate solution . ul h rntrate •·•· ····s p ate equation: + soluble salt -+ -+ insoluble ...75 - Chemistry IGCSE (Dr... + .:. 2 lead sulphate is filtered off arid washed with distilled water and then allowed to dry.-"sodium . Making the insoluble salt lead sulphate [pb SO.I t precipitate of lead sulphate···-----. Fa thy Abdel Galil) Making insoluble salts Salts which do not dissolve in water have to be made by the process ofprecipitation.(s) + 2NaN0 3 (aq) i (aq) means in aqueous solution (aq) (aq) + (s) means an insoluble solid -+ (s) + (aq) These state symbols show that a precipitation reaction has happened. .· . Precipitation is the formation of it solid when two solutions )> are mixed together.] 1 soluble lead salt+soluble sulphate sodiurTI sulphate scilution Je3d nitrate solution The two solutions are mixed together.. }> Making the insoluble salt silver chloride [AgClj AgN03 (aq) ionic equation: Ag+ + NaCI (aq) -7 AgCI (s) + cr -7 AgCI ._:_"'-'-~'-' General reaction: soluble salt Word lead· ••._. An insoluble precipitate of lead sulphate is formed. + salt soluble salt lead sulphate sodium nitrate + Symbol equation: Pb(N0 3 ). ~ + NaN03 (aq) . ••• . .. reaction. 2 . S~eam ~ g~ven 2..ha.-··· .. This is a reversible. Canden. the colour changes from white into blue.o carr~~<rr)~~irh. Test for Water [chemical testJ Add anhydrous .tue -·-> wiU:te de..t~ Cobalt chloride _____ _ If the water is removed by heatipg. blue. -- .tawr. c.atian a. If water is added to the anhydrous powder.·' Heating copper( 11) sulphate crystals (hydrated) 1 /~' I r: .crystals are heated. Here are some exampl~s of hydrated salts : Name EalUE~ Magnesium sulphate HgS0 4 ·7 H2o CoClz • 6 H20 - c~so~:s-H. Ca. the crystals often change in appearance and the anhydrous salt is. Physical test for water Pure water boils at 1oooc and freezes at ooc Heating cobalt( I I) chloride crystals (hydrated) CoC! • 6 H 0(s) 2 ~k._~~::_- a66 ~he ~ap ~e ~ube I.hydnttion CuS0 • 5 H 0(s) 4 + 2 hydrated copper( II) sulphate (blue] hydnttion anhydrous copper( II) sulphate [white] Wh_-n these.1/1' .. it gets very hot and changes back into blue copper(II)sulphate (hydrated}.76 - Water of cryst:z!lisation Some salts contain water molecules in their crystal lattice. Fathy Abdel Galil) . Anhydrous copper(II)sulphate can be used in this way to test for water.7.ng <U 61Wm b. fo-rmed. These salts which contain water of crystallization are called hydrated salt..Chemistry !GCSE (Dr.copper(II)sulphate. steam is given off and the· crystals change to a white powder called anhydrous copper(II)sulphate.---- 3.t a6 copper(II)sulphate crystals (hydrated}. ic.. Calcium carbonate + Ca(OH) 2 (aq) (g) (lime water) Explain why carbon dioxide turns lime water milky 7 o.d__ioxide - Sulphur ·trioxide S0 Phosphorus(III) oxide P203 NQ 2 Si0 2 Nitrogen qxide.~.p. co 2 so 2 (arbon ·dioxide Sulphur .) o nci 2 3 They react with acids to form salt and water CuO + .l.77 TYPES OF OXIDES 1.+~ . ... oxide. ~s-AJ. ~r't~.s a~~ ~~ Joluble f Potassium oxide K 0 2 Sodium oxide Na o yes pH 14 yes pH 14 pH. . . Fathy Abdel Galli) ..d. 12 Calcium oxide 2 CaO Magnesium oxid e MgO no Copper(II) oxide CuO no Iron(III) oxide Fe 1. t~ . 2.p.LJ'n.) Acidic oxides react with bases to form salts and water.) yes -) C)lS0 4 + H20 If they dissolve in wat er they form Na 20(s) + H20(l) ) alkalin~· 2 NaOH (aq) solutions • . .Ql~te. I~:> dioxid~ Silicon dioxide 3 ~e4-l:>otuble yes pH 6 yes p~ l yes pH l yes pH l ? -··.H2S04 2. h. Basic oxides· are the oxides of metals I.S..t$.·.§. ·. ~~..··.. yes no 1.) Acidic oxides dissolve in water to form acidic solutions.b. (vu~rbon -y co 1 dioxide + Calcium hydroxide -7 ..a£ 2.c.PH l ..· . ~he Acidic oxides are usually oxides of non-metals· Ac.Chemistry lGCSE {Dr. J.Jte.e.g.oo. e.c.· -(3) . u. they react vith both_alkalis and acids to form salts and . zinc 7 \e. NO_. oudu 'a. e.tub.· · 3.f.:·: alkalis. oxides (oxides of metals) acidic oxides (oxides of-non-metals) alka~~--r-~ salt+ water 'r"- acid or alkali amphoteric oxides (Ah0 3 and ZnO) Question: Complete the table that shows the reaction.tvr.78 - ..t. Amphoteric oxides are the oxides of certain me tals .e.u.n.Vt. i. CO .· Ampho. Indicate a reaction with "R" and no reaction with "NR". Sodium aluminate + water Neutral oxid e s are the oxides.c:J They have the properties o f both acidic and basic oxides.<. Fa thy Abdel Cali!) . Aluminium oxide + hydrochloric acid + Aluminium chloride + water 6HCI 2 AJCh Aluminium oxide + Sodium hydroxide 4. basic.e .<..'Wa ter. oxide type of oxide· magne·sium oxide basic aluminium oxide amphoteric silicon(IV) oxide acidic reaction with acid reaction with alkali ··. . which do not dissolve in acids or :. if any.Chemistry IGCSE (Dr. of the oxides with acid and alkali. aluminium.n. .q. of . sulphuric acid and nitric acid Test Add aq. paper blue). Sulphate (S0 2- 4 ) [In solution] Acidify.1\gCl Acidify. then add Yellow ppt. then add White ppt. (e • g. Fathy Abdel Galil] . Nitrate (NO. barium chloride HCI (aq) H 2S04 (aq) HN03 (aq) .-+ AgCl 2 aq. lead nitrate Iodide ( I ) Acidify.Chemistry IGCSE [Dr. hydro- J chloric acid) Chloride (CI-) [In sol. then add White ppt. co produced 2 (turns limewater milky).ut!on] Acidify. (t. of Baso aq. then little Ammonia produced aluminium powder). 2 Result - Effervescence.urns damp i:ed litmus warm· carefully )> Complete the following table to differentiate between hydrochloric acid. barium chloride Ba 2+ + S0 2"4 (or barium nitrate) -+ 4 naso4 .79 - ·:-· Identification of Ions Test for Anions Anion Test· Carbonate Add dilute acid ceo. Add aq. dil.) Tin solution] Add <J.·. aq. silver hitrate . of PbCl Ag+ + Cl. silver nitrate White ppt.. then ·-add . of Agi [In solution] aq. sodium hydroxide. silver nitrate (or Pbi ) 2 (or lead nitrate) . . Fa thy Abdel Galil) .towU'.e. Copper (II) [ Cu Blue ppt..e due .e. ..e.. :Blue ppt.ti. .to u4e.o . c.o. of ' ~ ' giving dark blue solution ' .-White ppt.tio n) Iron (Ill) [Fe 3+] Red-brown ppt. of Cu(OH) 2 . - in excess -~ed-b~own on the .of White ppt..ti. -- - / ---.o n J ..Wg \ a. ppt . ----. t I -Al(OH) 3 I I 1 / • ' \ a.o o.Chemistry IGCSE (Dr. .o.luble · Dirty-ereen ppt. / .- 3 Alumlnlum [A! +] ' White ppt.o.. Test for Cations { r Result ofadding aqueous ammonia Result of adding aq: sodium hydroxide ' Cation ...o l Calcium [ ca2+] White ppt./ [A.- - . ' .... -----.de.iv. insoluble in excess Ammonium [NH:] Ammonia is produced on warming with uq.a.o o.- - soluble ' \ I in excess {g-iving I I ( a..o..c. insoluble in soluble in excess {g-iv-ing.o 6otut£on) 1 ' ..e.OWt. . ~ •.-.c.to axJ..---. .. c.6a..-----_. of Fe(OH) 3 insoluble in excess Fe3+ + 3 OH ---+ Fe(OHh in excess ~ 2 Zinc [ Zn +J • .' I excess -. . sodiu1u hydroxide -' excess~ Dirty-green.Ao xJ. Cu2+ + 20H.....towU'.u.__ inso...-7 Cu(OH)z Iron ( II l - --.80 - ~:.e. of Ca(OH) 2 No ppt. of Zn(OH) 2 ' I' ' I soluble in excess {g. insoluble in excess ] ' [Fe 2 +J ' Fe(OH) 2 excess insoluble in {tuAno -- . soluble in ~ 2+ .o n) .. c.t{OHJ 3 and Zn{OHJ 2 ~e 0111photeM.da. ~ .o.-.--- - .o .u.- - - White ppt. hyd. insoluble Red-brown ppt. An alloy is usually a mixture of two or more metals or of metal and a non-metal.. 6...tin.. 2... Ex. They have usually high densities 3.. . .. ..opp~ and .oJr..... . They are malt~bte (can be ham- mered and rolled into shape) and du.. .. Metals are shiny (lustrous) Yhen freshly cut and polished. .bon." . &...........teeL ~ an aLLoy o6 . .81 - Chemistry I GCSE Topic 8..... because the atoms are packed closely together in a giant structure.. This is because when force is applied to metals. . Hetals conduct electricity because the electrons can move about inside the structure. ~--y~·············~························· Alloys 1........UC... . . Alloys are formed by mixing molten metals together and allowing them to cool.... 5. ... ...... S... . : B4aoo ~ an aLLoy on eopp~ and ~e..s of heat • .ampleo on rllo y~o .. . .... (Dr... .. the la~Jars of a toms can slide. They usually have high melt'ing 4. ...... Hetals are good conductor.e (can be stretched into wira)..ctU......... . . . over each other. .. ..on and c.... 2..onze ~ an aLLoy on c. .. ... points and boiling points. Fathy Abdel Galli) Metals and Reactivity Series Physical Properties of Metals _ 1.. ve a.gh m. IU.tlr)_c.d a1.oed e. g£EE0_.di. Making brass which is an alloy of copper and zinc . which is an alloy of copper and zinc is stronger and harder than the pure metals.g..Ute6 bec. 3.tolt o6 el.ec. good c.:ty. b~L>. L6 a.c.Jthea.a.tow Jtea.te6 ha.LL6e c.wn el. 2.tee1.ta. In· el. In c.b.oo!U.p.· 0 • me.Ue.ondu.to m6 o..ng u.oppeJr.Chemistry I GCSE (Dr.wrU. L6 du.o11.cy (ov/ overhead C<l. co11.iU.a.b.ec:tiUc w.andu.tert.al.e L>.oe c. c.lloy ·.c.e.c.u..thvr.c. a: good .t L6 u.a.tJUcA.: I. than any one of its eomponents. The following is a diagram showing the structure of an a. metal dom6 Uses of Metals related to their Properties Aluminium high electrieal conducllimy yens..vU!f a:nd haL> a.t.6ili beCJJ.8 2- Alloying often results in metal which is stronger.e. Fathy M. window frames cans Food containers aluminium The L>. Abdel Galil .teel.tolt o6 hea-t. For example.eng. : 1.then6 .the c.b!es aircraft (aeroplanes) carengihes Ov e. c. L>.oppvr.£ a.ec.t11. on .f. ....U + Hz a.....te..83 - Chemistry I GCSE (Dr......c......--.... .... calcium + water ----7 calcium hydroxide + hydrogen Ca (s) +2H20 Q) --'-+ Ca(O~ (aq) + H2 (g) St~te two observations you could make when a small piece_ ofcalciu~ Is added to cold' water....k Lll:lteJL --r hy d!to :Ude..........tta..m ---'7 o:Ude + ...........l ::.. [2] ...Jte. extracted by electrolysis a......Uh c.._.. + Hz Jtea....Uh d..-.cJ. ......me wct... ( see page-49 J Calc·ium reacts raadily but not violently Water with cold water to form hydrogen and calcium hydroxide solution.. ->a............te.... Calcium reacts steadily wi!h walet........ Observation 1 ·-···-····-·····--··················--···--.c...te.a...duc ed w.........t Zn .... Mg C-+ A.tta....... Jte..........Uu........Mbo rt w... Observation 2 ·-·-·-·--------........t.. Hz Fe o:Udu a....................do Pb (H) Cu Ag Au Action of· Water on Metals a) Potassium.Jt..ck ............. the alkali -U.. a.............................. Sodium.... Calcium -------------------------- Reactive Metal + Water ----7 Metal Hydroxide + Hydrogen Potassium and sodium react violently +----+-Hydrogen · with cold water. Fathy Abdel Galli) Reactivity series K . . Fathy Abdel Cali!) Magnesium Reacts very slowly with cold water to form hydrogen and magnesium hydroxide.. steam and dilute acids.rlnc sulphate + hydrogen Zn(s) + )> )> )> It is too dangerous to react the very reactive metals potassium and sodium with acids and would caitse aplosion. .· rI When heated in steam.vater. ri nc + Zn(s) + zinc + + hydrogen hydrochloric add ... • ( s) + • • • • • • (g) --> H O(g) ·-> 2 Hydrogen burn1ng React only with steam to form hydrogen and the oxide. oxide) Heal Magnesium + _Steam Magnesium oxide + Hydrogen Mg(s) + • • • • • • • • • • .. . rinc chlor-ide + . sulphuric acid --->.. Aluminium seems to be unreactive due to the protective layer of Al203 . magnesium turns to a white powder (magnesium... Reaction with Dilute Acids Metals above hydrogen in the series react with dilute acids and hydrogen is produced...-.. ...84- Chemistry IGCSE (Dr..:....7 . Ag and Au do not react with ·. This is a displacement reaction in which the metal displaced the hydrogen of_ the acid. Remember that Cu.. :i)e reactivity series. It combines with oxygen more strongly. . will reduce the oxides of zinc and of metals below it in the reactivity series. c ---~ iron ~··Fe_ + carbon dioxide + .. iron( Ill) oxide + aluminium-+ Iron +2 AI i.e.:he metal by heating it ·with another metal which is above it ir. :. i. iron (Ill) oxide _+ ··Fe 0 2 3 + carbon .85- Cherr:lstry IGCSE Making hydrogen in laboratory: Hydrogen is _prepared in laboratory by reacting zinc or magnesium with -dilute hydrochloric acid or sulphuric acid.. Fathy-Abdel ·calif) . Aluminium is more r~active -------7 2 Fe + aluminium oxide + A! 2 0 3 metal than iron..-e. <. so it can reduce iron oxide. more reactive. on heating. co 2 Competition for Oxygen : [Reduction of metal oxides by a more reactive_ metal] A metal oxide can be reduced tr:_ ·.·: : . acid hydrogen water zinc Reaction of Metal Oxides with Carbon Carbon.-(Dr. Fe(s) + CuS0 (aq) ----7 FeS0 (aq) 4 4 ionic equation: Fe ( s) + Cu 2+ (aq) ----7 Fe 2+ (aq) + Cu(s) + Cu(s) A metal cannot displace another above it in the reactivity series.. 2. 4.07/. Similarly.. .. . from magnesium sulphate solution. Finding the order of reactivity of metals : Ey placing a metal in an aqueous salt solution of the other metal and observing if displacement takes place or not. Cu ions are reduced by gaining tWO electrons and forming a solid deposit of Cu atoms... if a piece of Cu was placed in iron(II) sulphate solution.·· Displacement Reactions Any metal will displace one lower in che reactivity series from aqueous solutions containing its ions. no reaction occurs. . but copper displaces silver from silver nitrate solution (silver is below copper in the series). Thus.edox reaction in which iron atoms are oxidised by loosing 2+ 2+ two electrons and going into solution as Fe ions. copper does not displace magnesium. a reddish-brown deposit of copper forms on the"iron and the blue colour of ·che solution fades._______ -p~~~~ry/. 3. ..... ..86 - Chemistry !GCSE (Dr.. If a piece of iron is placed in copper(II) sulphate solution (blue)... . .... This is a Jr.ry~--------4 copper( II) sulphate silver nitrate V = = r. . aqueous solution Iron· zinc copper sliver zinc sulphate Iron (II) sulphate __. Fathy Abdel Gali!) :.eaction occurred no reaction Arrange the above elements in order of their reactivity (the most reactive metal first) l. uncombined in the-earth's crust The other metals are always found as compounds : oxides. silver and gold. Zn Zinc blende Zinc sulphide ZnS Ore: minenil found in the earth's crust from which metal is extracted . i. A stable compound is difficult to break down or decompose. the more stable its cr.·. the more it 'likes' to form compounds.+ oxygen heat 2Ca(N03)2 I 2Ca0 + 4N0 2 + 0 2 decomposition ·gets easier down the seri ~s ) Pb Cu Cu(OH)2 blue heat CuO+ H2 0 black ) 2Cu(N03)2 blue heat ' 2Cu0+4N0 2 + 02 black The breakdown of the compound by action of heat is called thermal decomposition.e. are ever found as elements.87 - Chemistry IGCSE . The more reactive the metal. 2.' nitrogen dioxide (brown gas).: Things to remember about the reactivity series : 1.(Dr. Fathy Abdel Galil) . Action of Heat on Metal Hydroxides and Metal Nitrates /Metal II Hydroxide Nitrate II do not decompose K KOH Na NaOH Ca Mg AI Zn Fe heat heat heat ) Ca(OHh heat . sulphides and chlorides. The tnore reactive the metal. I no reactwn ZKN03(s) I 1 metal nitrite+ oxygen heat I ZKN02(s) + 02(g) i no reaction metal oxide + water heat ) CaO+H20 decomposition gets easier down the series heat metal oxide. Extraction of Metals: Metal Ore Compound Formula Method of Extraction A! Bauxite Aluminium oxide Al203 Electrolysis of molten Al203 Fe Haematite Iron(III)oxide Fe203 Reduction of the metal oxide by coke (carbon) in a blast furnace . carbonates. S~ only copper.'mpounds. Compare what happens when these hydroxides and nitrates are heated. by reduction in a blast furnace. haematite. A blnst of hot air causes the coke to burn. carbon dioxide + + irori oxide . an acidic oxide to form 2 liquid slag which runs down to the· bottom and floats on top of iron.> Ca') SI0 2 calcium silicate (slag) CaSJo 3 .. · • calcium oxide·+ silicon dioxide --. CaO reacts with Si0 . carbon C(s) carbon monoxide 2 CO(g) ----.. fe 2 o .~) + ----. Iron ore. 2. Fathy Abdel Ga!ll) .... carbon + oxygen carb. The purpmse of limestone is Co remove the s~ndy impurities.88·- Extraction of Iron iron(III)oxide.Chemistry I GCSE (Dr. 2 a) Limestone is decomposed by heat calcium carbonate ____. 2 basic oxide.. .>->- carbon monoxide Iron 2 Fe + carbon dioxide + 3 Co 2 As iron reaches the lower part of the furnace it melts and runs to the bottom of the furnace. 1.on dioxide C(s) + o 2 (g) C0 (g) 2 The carbon dioxide rising up the·furnace reacts with more coke· to form carbon monoxide which reduces the iron oxide to iron. calcium oxide CaO b) Th~· !1 + carbon dioxide + co . Iron is extracted from iron ore. in 3 large quantities. 3. coke and limestone are added at the top of the blast furnace. mainly silicon(IV) oxide [Si0 ). t IU(h. contains nickel and chromium. In o. and chemical plants cutlery .:4% carbon].called cast iron. used for railwey lines and _bridges and building construction 3. l1ost cast iron is converted into steel. It is brittle and impure [contains about 3 - 4~ carbon]. ~~-~~~~-1~~-~2£~-~~~~lL-l~~q-~~2~1 contains about 0.t}. where carbon is oxidised into carbon dioxide and pure iron remains. Fathy Abdel Galli) Cast Iron The iron produced in a blast furnace is . ~·.E2£!!_~~g. 3. carbon.ther words. e.ough the molten . imr:>urities /. steel has a range of hardness depending on the car body percentage of carbon.rron [ containing . !i~a!!-_£!¥.89 Chemistry IGCSE (Dr.> no. z. molten iron containing .25.. stainless steel [doe. the steel becomes stronger and harder. and is used for cutlery and surgical instruments. Making Steel Oxyg~n is passed tl:ir.1.!?:f contains about 1% carbon.g. u·sed for car bodies and machinery. As the carbon content is increased. The required amounts of carbon are added. tvu paUu.d. ~~!~~-~E~~~-~ Brass is an alloy of copper (60%) and zinc (40%).m-6.Jt.e..6.x:ide 2 Zn(s) + co 2 (g) Uses of Zinc l. Re. coating (galvanising)· corrodes instead of steel.cycling metals stops them causing pollution and spoiling the environment.90- Chemistry lGCSE (Dr. ----') 2 ZnO(s) Zinc oxide· is then reduced with carbon (coke) 'in a blast furnace. ZnS.e. Foli. . cl.6 ca..oo. 3. .k. Extraction of Zinc Zinc occurs as the sulphide.e. zinc oxide + carbon .C..haUJi_ce.. pa.e. R~cycling makes sense because : l.tte.pe. that is... l. meLted dawn :to ma.mp. T!Uo -"a.olie.xa.-6 a.ve.ng o:the.e. The blende is roasted in air to the oxide ':. o.. It saves money and energy for extraction. <. neW bo:t:Uu.cyc.d g!.tion pltob.o.2. ~~!~~~!~!~g-~ The metal is used to protect steel objects from rusting. It solves the problem of waste disposal.U be.o. the zinc. Re..-0 Jr. zinc sulphide + oxygen (air) ---7 zinc oxide + sulphur dioxide 2 ZnS(s) 2. 2. Fa thy Abdel Cali!) ···. ·zinc blende.u can be.nd .: .teJUaLs : G!a.e.nd p!.U.Jt ma. Jr. e. ·~ RecyCling Metals All metal'S can be recycled.f.6.a.:. to melt down used metals and use them again rather thac throw them nway.6 bo.th a..n a. .cye.es are limited and cannot last forever.te.7 zinc 2 ZnO(s) + C(s) + carbon dio..a. It saves mineral resources since resources of or.. ·.. (rust) Rusting occurs . for rust.. Iron + oxygen + water --.-hydrated iron(lll) oxide 5..such as sea water.called ·IULbWrg . . Z...Uon Name the solid-left : Air and water TUBE A TUBES Boiled water Dry air TUBEC .... 4. ···········~·· .. ... This is the..rt hydrated iron(III) oxide..... Rust is the red-brown flaky nolid which forms ons iron and steel. chemical name........ •oooooo••••~••••. slow oxidation of' iron to for.. ). TUBED oil to slop · air dissolving In the water distilled water sea water boiled nails heavily rusted naUs rusted no no rusting rusting An e.. _conde... Fa thy Abdel Galil) . Rusting is the. . ·-2..rnrticularly quickly in water containing dissolved ionic impurities . ······~· .Ma...oooooo••••••••oooooouooOO!''"''uoonoooooooo What happens when rust is heated 7 . Both ~ nnd waXe4 are needed for..... corrosion of iron and steel is· ....> Suggest what elements rust contains... 3...... rusting to occur.91 - Chemistry IGCSE Rusting The.. ' ....(Dr.xperimenc co investigate the conditions needed for roscing.•••<oooooooooouoooouooooooooouooooooooouoooooooooooooooo..••••••••••~•••...· l. ct the steel legs from rusting. ships' hull or underground pipes. Iron and. galvanising or electroplating the iron surface. s~~6icial p4ote~on : Block of magnes~um ~r zinc are attached to the iron.. Fathy Abdel · Galil) Methods of Rust Preven-tion 1. The magnesium or zinc (being !!lOre reactive than iron) ar~ oxidised in preference to the iron..ateel can be protected from rusting_ by preventing air and water from reaching the surface. . [2] (ii) From the reactivity series name ariother metal that could be used for the blocks in place of zinc: [1] . oiling. zinc blocks fixed to hull )> Zinc blocks are attached to the steel legs of oil platforms (oil rigs) !• .· -· sea (i. This can be done by painting.g..) Explain why the zinc blocks prote. e.Chemistry IGCSE -92- [Dr . 2. ..... It is endothermic........ ..... This energy is in the form of heat..... i. CHEMICAL CHANGES ENERGETICS OF A REACTION All chemical reactions involve an energy change (ll...........(Dr.... exothermic reaction: endothermic reaction: HEAT / t HEAT HEAT · w·here does the energy change (ll....... heat is given out (the reaction mixture becomes hot).the following is equation for the combustion of methane (natural gas) CH 4 H I I + 2 02 o=o H-C-H H .. H). Making new bonds gives out energy...·..--·-. >.... which absorbs energy from the surrounding........... Fathy Abdel Galli) -93- Chemistry IGCSE Topic 9... An endothermic reaction is a reaction..... ..................e.............· . i. why the above reaction is exothermic .... -··........... Breaking bonds requires energy... ·... .... If the energy given out is greater than the energy taken in...... It is exothermic.... heat is taken in (the reaction mixture becomes cold ).... which releases energy to the surrounding..... An exothermic reaction is a reaction....from ? :· In chemical reactions bonds are broken and new bonds are formed.....- Explain using the idea of bonds forming and breaking........ and 4 x H-0 . the reaction will be exothermic.........->- and 2 x 0=0 o=c=o o=o We need to break these bonds: 4xC-H + We need to make these bonds: 2 X C=O ............ ....e....... H) come ....... . . . . .... ... ....... . ... . .. . . ..... .. ... . .... . . All displacement reactions are exothermic: 7 MgS04 (aq) + H 2 (g) 7 ZnS04 (aq) + H 2 (g) By measuring the rise in temperature we can find mit the order of reactivity of metals... 2... .. ... . .. .. 21) = 13°C > Why a polystyrene (plastic cup) is used instead of a beaker? ... . . Fathy Abdel Galil) -94- Chemistry IGCSE Examples (or exothermic reactions: ' 1. . hydrochloric acid HCl(aq) + sodium hydroxide-+ sodium chloride + water + HiO(l) NaOH(aqj --+ NaCl(aq) + fmal temperature= 34°C initial temperature = 21 °C temperature rises by (34. . .. .. . When dilute hydrochloric acid reacts with sodium hydroxide solution. .. a neutalisation reaction happens.. . .. )> Predict what the temperature of the reaction mixture in the experiment would be after 1 hour... . . .. ...... .. . . . Explain your answer.... . .[Dr... . . . . All neutralisation reactions are exothermic. ... When it burns. ..95- Examples (or endothermic reactions: 2 NO(g] 1. It causes no pollution because the only product of combustion is water.t . ~carbon ------1- diox1de + water J ) ) co 2 he. methane + oxygen CH 4 + z 02. needed for the reaction to take place Thermal decomposition. Hydrogen can be used as a fuel for cars.... Melting of ice and evaporation of water.a. ethanol + oxygen --7 carbon dioxide + water +30 2 --72C0 .{. ~ burning reactions are exothermic.>1 Burning Fuels Fuels release heat energy when they burn in air or oxygen. -. When i t burns. Nuclear Energy Uranium. J given aU-t ) What is needed for a fire ? Hydrogen as a Fuel Hydrogen is a possible energy source of the future.t . PRODUCTION OF ENERGY .a. 2 +3H 0 2 ) he._ ···..235 as a source of energy [see page !9]. This means that energy is 2. .·.Chemistry IGCSE (Dr. Fa thy Abdel Galil) .. 3.----~---- ~- . given 'ocU Ethanol (used in cars in Brazil).{. Natural gas i~ largely methane. ....· water i) wick draught shield j 0:.. . . . .. . . .. .. ..... . . . . . The initial and final temperature of the same v-.. .. . . . . .. .. . . . . . . . . ... .. . . . . . . . . . . . .. .:.."r... I.. . .. . .. .. . ... . . . . t :~:~· .. . . ... . . . . . _.. . . . . . . . ..... . ... . .. .. . .. . . .. . . . . .. .. ... r---- ----- spi rit bu mer l iquid . . . . .. . .. The same mass of each fuel is burnt in turn.. . . . . . . . . . . . . .. ..Chemistry IGCSE -96- (Dr.. . ' . . . .. .. . .. . . . .. . . . .. . . . .. .- fuel Questions: Suggest how you could work out which fuel produced more energy . . . . . . .. .. ... . . . . . ... .. Fathy Abdel Galil) Comparing the amount of energy produced by the burning of different liquid fuels: The apparatus below could be used.. ... . . . . . .. .. . . . ... . . ... .. .iume of water is recorded metal container f-- thermometer clam p :. . .. .... . . . .. . . . .... . . . What are the sources of errors in the above experiment? .. . . . . . . .. . . . .-. Fathy Abdel Galil) -. · ..-.l l l Zn Fe Pb H Cu Ag Au dilute acid :> The voltage of an -ironicoppercell is about 0.-.----. Electrolysis (endothermic) Electrical energy ----------__:~ t Cell (exothermic) Chemical reaction Simple cells Two metals that are far apart from one another in the reactivity series are placed in an electrolyte. The rule is : The further apart the metals are in the reactivity series the more electricity is produced.-..-97- Chemistry IGCSE (Dr.8 volis.. The amount of electricity produced (voltage) depends on the position of the metals in the reactivity series."''"'"~'··-.- ··--· -.-.-. The more reactive metal becomes the negative pole from which electrons flow.··.· Electricity from Chemical Reactions : Cell : a device to produce electrical energy from a chemical reaction This is the reverse of what happens during electrolysis. Explain your an?Wer..-.-----:-. Predict whether the voltage of a zinc/copper cell would be less. voltmeter Mg AI copper .-.-. where chemical reactions are brought about by the use of electrical energy.. the s·ame ar bigger.... .. The Zinc Carbon Dry Cells: [Batteries] Batteries are convenient source of energy because they are portable and small............. ... and are used in toys...... -=1--.... passes as ions in the solution.... 0 .. • 0 • 0 .................. • • • ... Fathy Abdel Cali!) ....... 0 0 • 0 ................. The more reactive metal is the one which loses electrons and i~e.......... becomes thinner......... radios..dilute sulphuric acid .........Chemistry !GCSE (Or.. Question : :::::========= How could the simple cell shown below be used to find out if zinc is more reactive than cadmium ? ·- voltmeter zinc cadmium electrode electrod......... The direction of flow of e............. torches and many other things.98- The simple cell can be used to compare the reactivity of two metals l.............. 2... .....is from the more reactive metal to the less reactive one....:............ ... Plotting Graphs of Reaction Rates FoUow...ng ga..... j·: Iricreaaing the temperature. Increasing the.... concentration..e.... .... 4.i.... of a chemical reaction can be increased by : l/...& vo...tion by mea...twne : Take for example the reaction between magnesium and excess dilute hydrochloric acid : magnesium + hydrochloric acid--+ magnesium chloride + Mg(s) + 2 HCI(aq) Measurements made are ---+ MgCI (aq) 2 + gas volume and time. Fathy Abdel Cali!) ·..ng IUJ.... How would you know when the reaction is complete ? .. Adding a suitable catalyst.eac.. i....... 2....... Light (applied to a few re.-99- Chemistry IGCSE (Dr...._a_king the size of reacting par·ticles smaller.·..&UJU.... __....· Topic 10..... CHEMICAL REACTIONS -Rate of Reaction The rate l....yringe stop clock The volume of gas in the ayrin•... for exal'lple at the end of each half-minute........ the plunger can move out gas s..e is noted at intervals.te o6 1r.actions)..... increasing the surface area of the reactants.... 5. ph I.<> u. <>. reaction slower .the.the II. .f.the II.ac. When . e..the GJtir.a. an acid and Ciirbonate.the. cWLve.100- Chemistry I GCSE (Dr. the balance reading decrease as the reaction takes place.e.t. ovvr.Uon.g.. curve steepesl.e.the cwr.uwn cMbona. ca. .with time. Fathy Abdel Galil) Here are some typical results: Time/minutes 0 l 1 ll 2 2! 3 3! 4 4! 5 5! 6 6! Volume of hydrogen/em' 0 8 14 20 25 29 33 36 38 39 40 40 4D 40 These results can be plotted on a graph. raacllon over .tvr. The 6a. i.ve goe. / fast .o. curve llal.f.e. the rate of reaction can be followed up by measuring the decrease in mass of reactants . curve· loss sleep... teacllon fastest The reaction is which a gas given off.mon .. . Shape a 6 ..teepvr. slow time (s) .._.a.. as shown '. add .te. 2. . ..£... • ...Lt ma.g -L6 di£ 6-{..c.. flour mills and mines] : F.... ht a....y e.-duo:t a. this shows immediately that the reaction is faster for the powder calcium carbonate..g....l1... chip~ gas syringe 2 3 Time/minutes Curve A is steeper than curve B...uU :to bW!.••.. A m.d.. • • • • • • • • • • • • • • • • · • • • • • • • • · • · • • • • • .. th... The danger of explosive combustion with fine powders and gases [e. Why 1A th-U ? ' .. ba...te..e..•...••••. o6 {toW!. i6 ~paJtk.rid a..... chalk powder and marble chips) with equal volumes of the same hydrochloric acid...ha. _produced co 2 can be measured using a_~as syringe and is plotted against time. The result shows : The rate of a reaction increases when the surface area of a solid reactant is Increased.ix.. ...tode..11.e....... The volume ~f.toW!......Chemistry IGCSE Investigating the Rate (Dr.. 4 5 ..g.. A = U<Sing c.... B powde.!Ol - of a Reaction Effect of particle size This effect can be examined by reacting equal masses of calcium carbonate with different particle sizes (e. Fathy Abdel Galil) .......t ~ U<Sing maJtb.twr.xp........ '··.cta. ' ~ .tM.--..o if.taJ.tM.L6e -<. thelj Me both at thUJT.tec.'.ncJtl211ll-<.U.tion if.Vc.fuec. T/U. the uacta..the tu:Lte 0 n JU!.: ·. Man cu.a.~_..e.oc.. and.Jr..o nc. (yellow) • A series of experiments can be carried out using a solution of sodium thiosulphate and hydrochloric acid of different concentration.c..:t<..(... u.en. the clock was stopped and the time recorded..enoJte. .t-<..c. T/U.onc...xed. M the Jtea.otW between pCl.te on Jtea.theJT.6 a. The c.i. on paper '·-··-·· ·············-· . .lj CU. When the solution became cloudy and the cross was no longer visible.ncJteMe6 ... due to the pJr. cross drawn --f..the Jtea.aJ.tio n pJr._ JU-g hut c.c..tio n decJteJU e6 .c.Wa.the gJtea.....ng .o IU an the h.en.Chemistry I GCSE (Dr.(.nc.n:U Me nU.iU Whlj ..ac.tio n.. on c.tbo exp. \' t=. The effect of concentration can be also shown by investigating the rate of the reaction between sodium thiosulphate and hydrochloric acid : add dilute acid and start timing ·view from above the flask sodium thiosulphate solution ·.._.ti.the c.t Jta.oUJ.b. the faster the rate of reaction. .ota. ( i) (ii) The effect of "concentration can be shown by doing several experiments using equal masses of magnesium ribbon and hydrochloric acid of different concentrations.eed6 the c. At first the cross could be seen clearly.u decJtea.wlphu. Fathy Abdel Galil) . The results show that the more concentrated the solution. 6ec.o e and the tu:Lte o6 Jtea.c.ea.:t<. .l..eup~on on ..ll..tou.o u.tec.6 if.tio r«>. Effect of concentration A reaction can be made to go faster by increasing the concentration of a reactant.ng .one:ert.102- .n:U -<-ncJteJUV> the numbeJT.on on . ........ " ............. Fathy Abdel Galli) Effect of catalyst A catalyst is a substance vhich speeds up the reaction but remaitls ...... ............. Enzymes are biological catalysts......... .......... .... .s .... . ........... ........ ifuy 1 9tw••••••••••••••••. ..Chemistry IGCSE ... . .... decomposition takes place very rapidly.............................. ' ....filtered off at the end of the reaction.•••••••••~'••••OOOOOOOPO•••••••'••••oooo••••t gas syringe with catalyst without catalyst hydrogen peroxide lr---solution manganese (b.... ................r.... ............. ...... ... " .. [protein innnturc I At room temperature....:: The speed of decomposition of hydrogen peroxide is investigated using different catalysts..... .............. dried....................... washed.... ................ .... and reweighed...... ' ......- " " .. ..... If the manganese (IV) oxid-e J.... ..103- (D... State the precautions which should be taken to make this a fair test : ................. .... .......Utck ) time (IV) oxide nuestion : daa=•-=•"a................. If a cacalyst called manganese(IV) oxide is added.......chemically unchanged at the end of the reaction... hydrogen peroxide decomposes very slowly·....... ........ it will be found that its miss· has not changed.... the e06 ec. ed by expo<. In order for particles to react. 2 AgCI >2 Ag + CI 2 Such reactions which are affected by light are called photochemical reactions. o 0 o .tion<> lnc.- the rate approximately doubles. o6 <>uJL6a.U. . ··- . When the temperature increases by 1o•c. of.ome !tea.a.:tu!te on .:. a.the .Ldea.suspension. When a silver salt is exposed containing white to light. Fathy Al:""'el Cali!) .. figure shows an _experiment with silver chloride.Ugh:t.-Uon. collis~Qn increases and the· reaction _goes faster.ell-tlt.c. Effect of pressure : (for gaseous reactions only) Increasing the pressure makes the ··mo-lecules of the gases close to each other and the fre~uency of. The .e Mea.o.•••.c.• 0 0 0 I 0 o 0 o 0 o o 0 0 o o o o o o • ~ 0 o 0 o o o o o 0 o o o o o o o 0 o 0 o o o o o o o o • 0 o o o o o o o 0 0 o 0 o o o o . .U..they must collide.Chemistry I GCSE Dr. 92. .· c.tion . <. TUBE A: still while when foil removed TUBES: darkens Tne effecc of light" on che decomposicion of Silver chloride. uJLe :to .p.nd :tempeJta.t.~S!£~.c.t .Lon :theoJty :to ex..Uver chlorid~.•.!tea. and they must have sufficient energy to react. o6 . Explaining the factors affecting reaction rates: The collision theory The reason for an increase in the rate of a chemical reaction can be explained by the collision theory.the . Light has the Exposed to light REMOVE FOil V effect of decomposition of silver chloride.104- Effect of temperature : A reaction goes faster when the temperature is raised.the c. Investigating the effect of light ~- The <.<.&Un . silver is formed.onc.peed<.te o6 !tea.w.. Uu. When light shines on the film. silver is formea.e. sunlight carbon dioxide + water glucose + oxygen chlorophyll i. . carbon. > 2 AgBr + 2 Ag white Br 2 black unexposed Jt photographic film grey black remains white Photosynthesis: Photo..Chemistry IGCSE -105- (Dr..green chlorophyll in the leaves absorbs light energy from the.dioxide and water. The process of respiration can be represented as: . glucose + oxygen --7 carbon dioxide + water + energy . the process of photosynthesis is endothermic and the energy required comes from the sun Respiration: Respiration is the reverse of photosynthesis and is an exothermic process.synthesis is one of the most important reactions involving light. This is the black part of the negative. The. Chlorophyll is the catalyst. sun and uses it to make(synthesise) sugars from. The film is covered with silver bromide. The unexposed silver bromide stays white. Fathy Abdel Galil) Photography The deco"mposition of silver bromide· (AgBr) to silver is the basis of photography. both the forward and backward reactions are stilhaking place.. A B + reactants £o/W!a)td Jte.b. i . equilibrium shifts to right Increase In concentration Proportion of A and B Increased. Fa thy Abdel Gal ill . Energy change in reversible reactions: If a reversible reaction is exothc1·mic in one dit•ection it will he endothermic in the other. the concentration of reactants and products does not change. sulphate.a.. At equilibrium.(!) sUlphate (+ heat energy ] -7 f- anhydrous copper(m sulphate +water ··chemical Equilibrium __ _ When the rate offorward reaction = rate of backward reaction. of Cor 0 ·- Le. {cptilourless gases).::::=:::: ammonia + hydrogen chloride NH3 (g) _+ NH4Cl (s) ( w:tiite solid) HCl (g) ·.04> SH:iO) needs energy supplied · in the forni of heat to give i!nhydrqus copper(II).reailon: Change In concentration . hydrated copper (II) sulphate (CuS.c:Uon . energy in form of heat"is produced.i.106- Chemistry l GCSE Reversible Reactions A Jtevvu. Factors affecting the position of equilibrium Effect 'on "equilibrium &fthe. and water~ When -viater is ad<ie<Lto anhydrous copper(1I) stilphate·(CuSO~). .tn fact.c:Uon. is one which can proc~ed in either direction depending on the conditions under which it is carried out.t~ Jtea.(Dr. equilibrium shifts to left .e.dwxvr.d Jtea.A + ofsubstano/ · B - ' c + D '·'Proportion o(b!uid Dincreased. 1ncrease in concentration of AorB I.· · ·· . the· reaction is said be at equilibrium. ·. For example.. Hydrated copper(. c ba.c:Uo n + D products For example ammonium chlaride :. the err. th. ·.:ia.:==·z + NH (g) 3 2mol )> .e direction which produces fewer gas moles.. In other woras.:.eft.::. an increase in temperature favours the products.-:Sit.:u::. .H 3 The effect of chanee in gres·sure r for <>'aseous reactions l : a:::z:::z:::=m:a=:a::JZJ.:a:::. N2 2 502 + 3 H + 02 <-T 2 2 so 3 T-=:==j"> 2 NO + 3..=x:=o:::.do.:a:J::=c: Increasing the pressure shifts the equilibrium in the direction in which there is decJI.theJun. . i.4Ue in vohwre.-··. an increase in temperature favours the· reactants.. b) For ~ndothermic reactions.i.e. makes the reaction move to the right. Fathy Abde! Galli) Increasing the temperature makes the reaction !!lOVe in the direction that takes in heat (.::'..J:.c.tion).*"':::.c-=e=-==•=*'!'.c cUJr:e.::c. ma:kes the reaction move to the ]. a) For exothermic reactions.Chemistry !GCSE -107- (Dr.r:xi2~=~~::t=ti=:Q::=az::. i.e..e. i..-e. ..:.::::c=a:~at••====c..t. 2 N.Predict how the position of equilibrimii might ·change i f there were an increase·in·the pressure on the f61lowin:g e-quilibria + CO (g) )> __ 02 + 2 H2 (g) Why an increase in pressure does not affeCt the position of fhe following equilibrium : 2NO(g) ·~-~~·-··············································· . ························································~········ . Power stations are built near i:ivers or coasts so that they cart. first. 2- As a solvent: in many industries.Ch~mistry (Dr.. towers.g.Drinking 2. AIR AND WATER PuM.Washing 3.:teJL by liU. : ===. cut U.voirs.. In the. l :.abted Mom .6eo . PUJte wa. water for the cooling.<. o6 wa.:tUJ. bu:t . expe. some dilute sulphuric acid is added Hydrogen gas is fonned at the cathode and oxygen gas is collected at the anode. e.a:tWn.Cooking Industry uses water in many ways.:teJL Mppty : The water from rivers is. i·": .atio n a 6 wa. 2- Chlorination : :ell:====-=-====== Then it is treated with chlorine to kill bacteria. but it is not pure ·in the chemist's sense because it contains gases and salts' in solu~ion. To enqble water to conduct eiectricity better.t.eo.ve p!toc.a.. 3~ Manufacture of hydrogen and oxygen by ~lectroiysis of water.::======== It is filtered through heds o·f fine sands to remove suspended (insoluble) ·- solids.:teJL Household tap water is free from har~ful bacteria and insoluble dirt.n be ab.6. Fathy Abdel Galil) · -108- IGCSE Topic 11. At the su:toface. paper industry. stored in reservoirs where the process of purification starts. so the larger particles of dirt can settle out.QJ_c. is treated in two stages 1- Filtration : ===:.· light break down other impurities and kill some bacteria. The water is still.6e1t wa.========== 1. The water from the storage rese:z::. water is a very poor conductor ofelectricity. 1- Much water is used for cooling.JU.g.Jt c.:tJW. home . Electrolysis of water Pure. oxygen· and sun.U. have continuous· supplies ·of. e.:te. (b. 3- The different components have. different boiling 'points. so ·they can be collected in turn as they boil aff. -: 196"C) (2).p. Sepalr'a.t.{_on a 6 oxygen a.·neon.(Dr.8~ble gc + a tittle carbon'diqxid.?iu:ugon (a... 1- Air is liquefied by compression. .... -186"C) (3) oxygen .) -· ----=====:. argon (b._ 2- The liquid air is allowed to boil. -183"C) . (1) nitrogen .$and.Water vapour + sma!l~r amounts ofh~Jium. krypton and xe~on (the oth~r-6~blel'gases).·•· . : i .e~. Fractional distillation is used to separate the pure gases from one another .p. Fa thy Abdel Galil} -109- Chemistry 'IGCSE Composition ·of air - Air is a mixture of gases : nitrogen 78% (nearly 'A) oxygen 21% Gust over \1.p.nd /UX!wgen f/wm Uq!Ud lwr.:tt----the remainidg ·1% I_s~n. (b.riY:.. i• --' UJ z w __J Ol >- X· r::w 0 --' 3- () <{ In making steel FoJr.. e. TheJLe .a.ndte w.a.drUtion . rco 2 1.nno.Jtbonll· a..h you c.6 l- (Dr.ombUl>tion w!U.a.t -i.tU!> c.t .{..the exllO.aJt wgine.{. <>orne !Litbwr.aJtbon d. . ~ C0 +2 H 20 2 methane (natural gas) C H 0H 2 5 + 3 0 .de.il.:Uon o6 c.ol .de : 1- As a product of complete combustion of carbon-containing substances CH 4 + 2 o2 .6oo.{.Jtbon d. .omplde c.f.toude and Wll..the c.:.<>e-6 c.aJtbon (<>oo.nd .d. When pebt.td c.oc.theJL p!toduc.~>orne c. water and heat energy ·are produced. c.Jtbon monoude [CO].teJL. . a.aJtbon d.e a.o J.nc.110- Chemistry IGCSE o 6 o x_ygen : Pure. and C0 2 .oxJ.ent . 'medical grade' oxygen is used in oxygen tents in hospitals for persons having difficu+ty in breathing normally because· of illness or unconsciousness.cl.7 2 C0 2 + 3 H2 0 (ethanol) .iJ.t a6 -i. . :the po.tn.iome .6 c. 2 .ze aU..to oxJ.no. some of the oxygen in the air is used up.6 pJtod!..a.to .aJcbon ·monoude.tha-t :the a»t l>!Lpply wa.a.6.Jtbon .on:tain . TIUA p!tove. aL6o pll:oduc..g.:the ha.LbonoU1> :9a.U o6 c.ma.. Th. :the· hydJr.:L:.t ga.iJ.tl.n a. 2.nllu66.t ue olt ..~>me.ll.n:t hydltoc.a. Fathy Abdel Galil) ._oxJ. 2- As a product of respiration : During breathing. depo.In welding : .t). Some 6uw.iJ. Acetylene (which is an unsaturated hydrocarbon) burns m oxygen to give a very hot flame "oxyacetylene flame" welding torch c: Q) .aJtbon 6ue.6 . .U<> e.Jtmle-6. .c.6 b!Litnt bi :the c. Hethane is heated with steam over a nickel catalysc CO(g) + 3 H (g) 2 > The following is the equation of formation of ammonia from Its elements.-111- Chemistry I GCSE (Dr. :> 1. Uses of ammonia Making fertilizers Making nitric aCid . 1. i. 1NH3 (g) The reaction is exothermic. The reaction is reversible. Fathy Abdel Galil) Manufacture of ammonia by the Haber process : . Hydrogen in now obta·ined from methane (natural gas). Nitrogen is obtained from the air. The unreacted gases are recycled. ii.theo. 2. nitrogen and hydrogen·are combined together.U. nitrogen and hydrogen: + i. 11. Ammonia is made by ~yn.e. )> Conditions: temperature: 450°C pressure: 200 atmosphere catalyst: .iron Ammonia is liquified by cooling. Fertilisers are substances. Ammonia is very soluble in water and· aque·ous ammonia is .. For example• : NH. phosphorus (P) and potassium (K). Chemistry IGCSE .formed.8. choking gas. Nitrogen is the most important of the three elements because plants use it to make oroteins.. 2. 3. Fa thy Abdel Galil) =: Ammonia in the Laboratory l..Cl(s) . which is. Many fertilisers contain phosphorous and potassium compounds as well as nitrogen compounds..The major plant nutrients include nitrogen (N). 16. NH 3(g) ammonium sodium ammonia chloride hydro:x:ide + NaCl(aq) + H 20(1) ~p sodium chloride water red litmus paper :unmonium _ _____:~.112- (Dr.24 NPK FERTILIZER . + NaOH(aq) ____. Nitrogenous fertilizers: Ammonium nitrate Ammonium sulphate Ammonium phosphate Urea NB4N03 (NB4)2S04 (NB4)3P04 CO(NH2)2 4. it will neutralise adds to make ammonium salts..y chloride t warm 2. Ammonia is a colourless. which is a weak alkali. which added to soil to promote plant growth. NH (g)· + 3 >- + ~---these H 0(!) ---+NH 08(aq) 2 4 ions make the solutionalkaline Since ammonia is an alkali. Ammonia + nitric acid ---+ ammonium nitrate Fertilisers 1. These mixed fertilizers are called 'NPK' fertilisers. . formed whenever· an ammonium salt is warmed with an alkali. Much of carbon monoxide comes from the in- complete combustion of petrol in car engines. They send sulphur dioxide int-o the air.6 a.<.t toweJt levw J.h.<. c. When burned.aJtbon monoxide w.y.opheJte.dioxide.zz.emogtobbt .<. wa.oloi11!1. Factories and power stations burn coal.a. nitrogen is also present.the btood t)Jtom c. so 2 : Fossil fuels (coal and oil) always contain sulphur.o.u a. some nitrogen with oxygen. Common pollutants in the air 1.even.U.n. CaJLbon monoxide .Mu hen.Ub u bJr.U ha.. on -U:.bbtg oxygen. These gases can cause air pollution and are called po~..hd... sulphur dioxide is formed.113- Chemistry . A:t a.nd .e. At high temper-ature. CO : Carbon monoxide is produced by the .nhtg 2.c.da..U po. a.tung d. c.Ut k.<.the. which contains sulphur..kl.<> u • In .tmo. oxides of nitrogen.nd d.UonolLb ga..<.a nc.Jr. uppeJt a.e~ Sulphur. Sutphwt d..n _. Carbon monoxide.o xide.·incomplete combustion of carbon con~aining fuels.nd odoUJLteM.nu.hu a. the result_.U.c.t c. 3..Mbon monoxide g. Nitrogen · + oxygen --l>- nitrogen· monoxide ~ 2 NO(g) Nitrogen monoxide + oxygen -nitrogen dioxide 2 NO(g) combines .<> ea.. Oxides of nitrogen : When fuels are burned in the oxygen of the air. tevet ot) H. Fa thy Abdel Galil) AIR. other gases such as sulphur dioxide. i l -Jtea. :thtLt pll.-6 pJtUenc.teJt :to 6oJun a.W wd.a. POLLUTION Apart from the gases normally _found in air.qc:U.b.<. and carbon monoxide can be present. Bebtg c.vu no wa.oo:r.dd JuU. c.!GCSE (Dr. Lead compounds A lead compound called tetraethyl lead·is added in small quantities to petrol to increase the octane number·of petrol. ·:the..ve. damage .hild!r.{_n.e. eaMe.. n.. ac.i.I 14- Chemistry IGCSE l· About 30 . . NO .t. The main way of preventing pollution from compounds of lead is the use of lead-free petrol (unleaded petrol). Me o6 l11'11.c. ~\ catalytic converter Nitrogen monoxide + 2 NO(g) + carbo~ ~·nitrogen · + monoxide carbO:n dioxide Ca:ta.J.Won..i. Lead c.t:Jtol.. b/W. where the toxic gases are converted in the presencR of a catalySt into carbon dioxide and nitrogen.v e and .g :to ac. of the oxides of nitrogen in the air come from car exhausts.Uc.i.Jt:toM !Le.i.to x.n.y c...t!togen. fuM. a6 n.tve .d pe.Jt . Other sources of nitrogen oxide pollution are factories and fires..{.nd!.o~>..dv.eade.(Dr.qt. po.y:Ue eon.n. Catalytic removal· of oxides of nitrogen from car exhausts : Catalytic convertors are now ·being fitted in the exhaust of cars·.n.d :the..d lead.{_n.i.. lead compounds are released from car exhaust.J. 4.e..Wte.n.~>. Me.6 hJ.i.ompou.aM. pa!L:Uc.ulM.an.g hty c. When the-petrol burns in the engine..to 6oJUn n. In.i.. 2 Ox. exhaust from of car eng ina ' ·.J.d /W. young c.407. wa:te.Vtve. Fathy Abde[ Galil) . M ..:to!L :to 6-Lnd :tlte. It removes minerals from the soil and increases the acidity of = 4) makes lakes too ncidic £or fish to live in.115- (Dr:. 3.q ttld.ta.U a.a.te.te.I'Lt hl:tu o 6 . :to fte.6 :tu:te.U. e.t I ndlc.tlo 11 and .i.tlte .Jt .pl:ta.dc(e.Jte. .dde:'ll J:. . o6 :the.ttLJte.o .6ttipfta. 2 Finding the acidity of the soli : I... a. 4.U..i'.Uve.qttld l.Jt) . Acid rain can speed ujJ corrosion-of metals.te (llt.U.tp p!Le. Some.ttbte ".. Acid rain attacks construction materials such f!S limestone and 4.M .6:t.e.e.d w. Lime [CaOJ or slaked lime [Ca(OH) J are used for neutralizirt(l acidic soils. Fathy Abdel Galil) Acid Rain Acid roln 1 I Harmful effects of acid rain l.x.p!Le. A !te. 6Jtont cU66e.U:ft . 2. Tlte c. Acid rain (pll 2. baJtlwn . the soil.Ut!Led.tlte <lcunpte.U.tn wa.n.cA. .w. pll. <1o.d :to . It is important to control the acidity in soil.6a111pte.Jt O:ftd .Chemistry I GCSE .. Wa. o 6 :tlte.6o£.tfte UttlveJL?a.a:k.bOil ll. ln a.tfte 6le.e.tdl l. be. 3.6 :tah.tlte nr.to cte. - ll6- Chemistry IGCSE (Dr. Fa thy Abdel Galil) !; [: Topic 12. SULPHUR A non-metallic element, yellol" solid, .. with low m.p., ll9°C. Large amoun~s are produced each year by mining as it is used to produce sulphur dioxide. Sources : a- Large amounts found in certain volcanic regions of the world. b- From sulphide ores [e.g. zinc blende] • c- Under ground deposits in the United States extracted as. liquid by pumping heated water into the sulphur depos.it. Sulphur·dioxide, S0 : 2 =======a============== Acidic :gas. produced by burning sulphur in air S(s) + 1- As a. food presecvative 2- B'leaching wood pulp 3- Making sulphuric acid, H so 2 4 Food passed through an atmosphere of sulphur dioxide. The gas kills bacteria that could spoil the food or be a danger to human health. When wood has been broken down to a· pulp ·it has a brown colour. In order to make. white. paper from the pulp it has to be bleached by passing sulphur dioxide through it. • ' -117- Chemistry IGCSE (Dr. Fa thy Abdel Galli) Sulphuric . acid ·is mad'e by the Con.ta.c.-t PMce6.6. This has 3 stages a) Sulphur is burnt in air_ to ·make sulphur dioxide I· b) S(s) + Sulphur dioxide and.more air are reacted together. );> Conditions : temperature: 450°C ,, catalyst: vanadium(V) oxide ; pressure: 2 atm. (for circulation ofgases),. (no need for high pressure] 2 S0 .(g) 2 + i>ul.phwr. cU..ox.J..de . c) o2 (g) 2 01(g) so 3 (g). ;,Ul.phliJr. . .oxygen 6iWm tWt. ruo x.J..de 1/t :tfieblly, 46 i>ul.phwr. :tJ;;;l_ux.J..de £6 rUbi>ol.ved .:l.ll. Wod:eJL, L>u1.plu.vc.tc. a.c:id .U pJwduced•. Ba:t .thU .U. no.t dime in p}(O.c.tic.e . :toa ex.o.the)!Jn)_e a.nd · on a. .ta.Jtge .6.c.al.e beaa.u.6e .:the Jt:e.a:c.tioir M boili :the <.ul.phwrJ.c. a.cU pMdU;c.ed. . •.... .{.- · The <.iLtplit.vr. ruo:dde -M rUb.ool.v-e:d fi.i.Mt. in c.anc.e.n..tJUl:ted ;,Ul.phwUc. a.dd :to 6ollm ol.e.um. S0 (gJ 3 + .6 u.tphwr. ..tliJ..o x.J..d.e ..U- H:zSb4 (IJ - ·· -.> H2SzLl 7 (1) .6 u.tphwrJ.e a.eld -.- .-> d ·· 0-<.-eunl 1he ol.eum .U then d.U.t.cted wUh the eoJUr.:ic:t·. amoiut:t o6· wa.teJL :to pJwduc.e ecmc.e:J1:tlu;(;te.d.L>u1.phwr..i,e a.ci.d. H s o (1) . + 2 2 7 ol.eum H 0(0 2 wa.teJL. -~> 2 H so (!} 2 4 .6 ul.phwr..Le a.c.f..d Since ·all three of these ·r·eaC:tiona are. exothermic, the whole process prod~ces heat en.e.rgy, The fact that enetgy is ·produced rather than . ' ; ' needed means· that sulphuric acid can be produced· cheaply. i- in-making :t~rtilisers (!'.g. ammonium sulphate) ii- ·iri making detergents iii- in making_paint;s i.:iii- ·iii. car batteries. Conc~e.d .6u1.p/w.JUe a.Ud .U paJ~y da.ngelloll.<l :to hamil.e becO.iJ.M!. U .U a. powvr..6u1. dehydJr.a:t.Utg agen:t. I:t w.i.U Jcemove wa..teJL 6Jtom otheJc. .6ub<.~c.u,. Chem!.~try IGCSE (Dr. Fa thy Abde! Galli) -11&- Topic 13 CARBONATES All carbonates a~e. insoluble in water exce~t-aodium, potassium and l. ammonium carbon~te. All cubonates .react wfth dilute aciqs, they all fizz and dissolve, 2. giving off carbon dioxide and leaving a solut'ion of a .salt.· Carbonate + acid salt·;+- .water + 2 HCI(aq) CaC0 3(s) + Cl!rbon.dioxide . CaCI,;(-ilq). + ·HzO(lY.+ COi(g) . ·.. - ., ... 3 •. They decompose upon heating to f_orm_-llieta'J:._.oxide .. i:md:.-;:,ar)>,on dioxide. --......,-.;:. + ·cbtfg}' C\iO(s} bia.c.li. Sodium and potassiurrt carbonate, however,~aretoo st<>bf~ to decompose .. i.e. they.haye.high thermal stability. Suggest what is meant by th~ tenn thermal stability. . . . · ............................ +···...... ·.. _.. ;; ....... ~---·· Limestone'.lime and- slaked lime : · .. .. .... Name Fonn!Jl? •. '. caco · 3 Limes. tone Lime [Quick· Lime.] . Ca{CF!l . ,. . 2· Slaked Lime· A solution of CaO ~ .. '• Chemical .. . . Colour Nam_e.~ Ca.rbOh~te .(alcium ... . .. Calc(um OXid~ Wh!~e ··-- .. .ca:icium •. .. Hy'droiddet .. · ··. .· ..· calcit~m hyd'r<ixi,d~' i~ .c,all,)<{i{:.:);im;·~t~i":.~::w!;!¢n Co 2 gas it; bubbled .. White i:hrou~h 1i1!),i::.<'w~~~;~~-:ti\:~_-~@i'iihi~J.b;,;.~(;&um carbo~S:te_ appears as a.-l{hi.c~ sifs{;-e~Ji~o~;:·:~~ 'i#i(!, ~$i~\l'i;':~(les 1 mi11W', ..-. ·.- WJ:tlte .. '. ...6a:~~ o{Um~ (C!CLtcWm ox.{.Neutralize aciqic gases and industrial acidic wastes.. they are used to : - . c). .. CaC0 3 M~nu6Q~~ o6 cement..lime B lime slaked lime c limestone lime D slaked lime lime . •. calcium hydroXide (slaked· lime) Ca ( 0 H) 2 As both [lime and slaked lime. . . important car:-bonate.is ..6a. Fathy Abdel Galil) . 2 water + .sa. reaction. It can be re·adily convert·ed (slaked lime]...<Mit.Chemistry I GCSE Calcium carbonate (Limestone) Formt.c.] form in water alkaline solutions.:::====== The diagram shows a lime kiln.~ I. Question· -:. .tWL~ o 6 .U!c). b) ..U.nd hnpu.nu.Jt. Calciuin oxide has important to calcium hydrol<ide. The symbol equation for the. neutralises acidity in the -soil d) Ma!1u.119- An. (. · What are X and Y? y X A . Ca(OH) ·calcium oxide· + (quicklime) CaO·· u~ea.!la : Usee : ~1 (Dr... by adding vater ---+ "---'-'r .Neutralize acidity in the soil · . Cement ·is made by heating together limestone and clay. ... limestone heat r heat t heat i:.Ma.to JLemov~ .. Limestone is heated to a high temperature... It decomposes to calcium ol<ide and carbon dioxide. HIO .'living'. . The term 'organic' means. HYDROCARBONS Hydrocarbons are compounds containing hydrogen and carbon and no other elements. ORGANIC CHEMISTRY Org. Fa thy Abdel Gal ill ..cw.mic chemistry includes the study of all carbon compoim.s.tuJuiL !P.ds except the very simple ones such as co 2 . methane H I CH. They are classified into alkanes [saturated] and alkenes [unsaturated). alcohols.I I H-C-C-H I I I I B-c-c~c-H I I I H H H H H H H I.a. 6~ed Name N!-imberof Mol<C!!LUVL carbon aroms 6o1Umlltz.o. 2 H propane butane 4 pentane hexane heptane octane . 5 Gen eJ!a1.H. 6oJUnul. Organic compounds are grouped into classes [families) such as hydrocarbons.120- Topic 14. 1 ... . organic chemistry was the study of carbon chemicals from_planta and animals. 3 H . I ..ynul. Now it is "known that complex carbon compounds can be made artificially.co and carbonates.Chemistry IGCSE (Dr. of carbon atoms] . I I H-c~c-c-c-H I I I I H H H H C.. H-C-H I H H ethane C. ALKANES They have single bonds between their carbon atoms. [n = no.a 6 7 8 H H H H I c.. organic acids.e. At first. i.H. the presence of the double bond.c.has two structures.pna£.ulM a.i.Mban. The different structures are called .C-C-C=C. they have a double bond between two carbon atoms. has only two carbon atoms. It is called ethene.. o6 c.bomeM.ctWLa£.l2l- Chemistry IGCSE ::·.C=C-H I ·H but-1-ene 4 but-2-ene 4 C4H8 C4H8 I! H I I I H ~ H H I I H !I I I H H H. Fa thy Abdel Gallll · . Le.(Dr. H H I I H-C=C-H H I 3 propene C3H6 6Ollmula H .thene ..C. different structures . Malec. The simplest alkene. ISOMERISM The alkene c4a 8 .. · Isomers are compounds having the same molecular formula but.oup.to/Jk\ 6aJUnula Name 2 e. but-1-ene and but-2-ene.I H I H.:ti.H t l H-C-C=C-C-H I I! I H [ n = no. ALKENES Alkenes are IJY!4a. C2H4 StJw. No. g/f.:tulrLLted· ·_hydrocarbons. which is called the 6un. of carbon atoms] Alkenes are characterized by. . .tonu... H methanol 1 CH 0H 3 I H-C-0-H I H ethanol 2 C H 0H 2 5 H H I I H-y-y-Cl--H H H H propan-1-ol 3 c3H70H I H I H-C-C-"-C-0-H I f I !l H H H ... alkanes.e..0-H propan-2-ol 3 c3H70H I I H I H-C-C-C-H f H f ...e:tu!r....a..regarded·as.. in which one hydrogen atom is replaced by a hy~oxyi g~up [OHJ........ -> 0 L]..Chemistry IGCSE (Dr.... ... butan-1-ol butan-2-ol ............. o6 caJrbon a......whi"h have the mol1>cular formula c H 0H are isomers.. Fathy Abdel Galil) -122- ALKANOLS [ALCOHOLS} Alkanols can be. Th·e alcohols butall-1-ol and butan-2-ol . Write down their structural formulae. No....... 4 9 . of carbon· atoms} 0 Propan-1-ol and propan-2-ol are H ·I ihom~.... Name. They are named after the alkane (with the same number of carbon atoms) [AN¥.. FoJrmul. I H R [n = no.. Sbw.. ............. This is called the 6unctidnal g4oup.. Homologous Series A 6a. .shn.n.. .vr. . acid • . ..tl. AU membe!Lb Me ILepiLruen:ted by ..nc.t bu:p. . . . .:::====== Draw the structure· of butanoic.C-O__:_H I' H 3 H H 0 I 1 II H-C-C-C-0-H .t/Urno. . .U'. .M e.ompou.same gene!La.Uy o 6 .ru :the bo.enru.sameJanc.aJLbon a. . .<. .s · :gM.U ••.g..nd me. ...ng a.J.c. . c.. 0 II [ -G-0-H] ...the piLIUence o6 . . . ..y A.. .s o6 c.tiona. . .s rvr. j I H li Question : ==:..n. . . . Fathy Abdel Galill [CARBOXYLIC ACIDS] They are organic acids and characterized by the presence'of the carboxyl group.123- Chemistry IGCSE ALKANOIC ACIDS (Dr. . . They are named after the alkane (with the same number of carbon atoms) [A N X --> 0 I C ACID]. .. .the . .d. .s .. . . . A..t)_ru due :to . acid· [acetic acid] propanoic acid 2 0 II H-.ogou. ..tk... a. e. .do wLth . . . o6 c.tom6 methanoic acid 1 0 II H-C-0-H H I ethimo:i. homol.s we go aLong a..ilalt OJtganic. .m... .du:a. .m. .. a.W.. ··---'---------------------------Name No.Uhtg po-i.ILe.s. .n:t.C. .. . p!WpeJL.the .. .. Cit ru. .ompou.i.. which is the functional group. .IUll ... .t 6o. . Fathy Abdel Galli) ORGANIC HALOGEN COMPOUNDS These are compounds formed when hydrogen atoms in an alkane are replaced by halogen atoms. is produced from burning fossil fuels. mostly alkanes Coal Black solid Mainly carbon Fossil fuels contain sulphur compounds. e. 1. which form·acidic sulphur dioxide [S0 2 l when the fuel is burned (leading to ac~d rain).eo. emission: co. Coal..e ''-'~ d Jteoowr. crude oil. 3 7 FOSSIL FUELS ' Fossil fuels [coal. crude oil and natural gas are -vu1~-U.. Fossil fuel Appearance What it contains Natural gas Colourless gas Mainly methane (CH4 ) Crude oil [petroleum] Dark brown liquid A miXture of hydrocarbons.n formed as a result of the decay of plants and animals that lived long time ago. chloromethane chloroethane ~ 'I 7 H 8 8 H I Br H-f-C-C-Br I H I H-f-9-y-H H H H 1-bromopropane 2 -bromopropane 1-bromopropane and 2-bromopropane are isomers. is a green house gas leading to global warming. co. natural gas] have be. they have the same molecular formula c H Br.-124- Chem!s_try IGCSE (Dr. nonrenewable source of energy. .c. Fossil fuels and CO. Uaru. (pe./'.66-i.IWtg.U.kenes are always formed as one of the products of cracking.de a.the hea..vi~ 6Mc. by ci piweu. CaU..y.Czsl crude oil __...t.125- Chemistry lGCSE (Dr._ The main fractions are : fraction used as fuel in cars (C (Kerosine)· 5 - c 10 J fraction for oil stoves and aircraft..tha.pply fiJtam the fuWf._ fraction for making waxes and polishes (over c 2·5 J heater Bitumen fraction for making roads In 6act.. 6aJttuna. The reaction needs high tempeJtatulte and a e~Lt~L.Jt~Leking. Fathy Abdel Galil) ·Fractional Distillation of Crude Oil Crude oil (sometimes called petroleum) is a mixture of alkanes.U. trucks and some cars (CJS .ty.nJ .t.. . the demand on ughteJ~ oiUJ.wl.c16l fraction as a fuel for the engin·es of lorries. piLIU1..xti_on a6 CJw..ed eiUJ. . Cracking The process of breaking longchained hydrocarbon molecules into shorter ones is called c. . gJtea. To make best use of oil.n the .they ean be made 6Jtom .t~ .ou.te. (Cg .moru.c. it is separated by fractional distillation into useful fractions according to the boiling range of the fractions. Al. ... . ..- .... . which are very useful for making plastics. . ... ... . .. .. Cracking a liquid alkane: The following figure shows a simple laboratory cracking experiment. ... .. .J.... Suggest why this is done? ......... ..... .. .... Hydrogen gas could be also obtained during the cracking of alkanes....... . .. ......... 3...The vapour of a liquid alkane is passed over a heated catalyst to make ethene. : . .... . )> The delivery tube is removed from the water before stop of heating. . .temp. It also produces alkenes. .. .. ..Chemistry IGCSE long hydrocarbon molecule Octane -126- ~.. ...... . . . . Fathy Abdel Galli) shorter alkane molecules hexane + ethene ------> Cracking is very Useful: 1.. . . liquid alkane + ceramic wool catalyst delivery· tube ethene heal heat water )> Suggest the function ofthe ceramic wool_.. . less useful fractions into smaller molecules that are useful as petrol [more benefit] 2. _CJUl~-'-cl"-u·'-"'"ng--> (Dr. It' converts larger molecules from heavier.. . .. . > c y... .. g · > I H-C-Cl I [. alkanes burn in air .{ H mc:thanc ·chloromethane Similarly. LL h't. H o and 2 2 heat energy is given out.. the next fifteen are colourless liquids and the ·rest are solids. Alkanes are generally unreactive. Saturated hydrocarbons undergo substitution reactions. + CH (g) 4 2 o 2 (g) (methane) --) ·· C H (g) + 5 0 (g) 3 8 2 + (propane) 3. . s.ght 2 · + HCl hydrogen chloride gas ) · C H CI 2 5 + HCI chloroethane This is called.127- Chemistry IGCSE (Dr.ubstitution reaction because the hydrogen atom in methane molecule is replaced by chlorine atom. + ethane Cl £<. Thus. 2. The first four alkanes are gases. 4. so alkanes are useful as fuels. Like all hydrocarbons. H H I H-c-H + Cl 2 I ..giving co . ehto4am~hane is slowly formed. Simple alkanes react with ehta~e gab in presence of !Lght. when methane is mixed with chlorine gas in bright light. Fathy Abdel Cali!) ALKANES Properties of Alkanes 1. so they all show similar che"in. + ethene . a.ical properties .:ti.128- f:~. H. Generally.JUj Jte.c. They undergo 2.:ti. They burn with bmok.ve.a.a.. Properties of Alkenes Alkanes are members· of a homologous series.ted) is formed •. H H I I I Nl ~ k "'"'"' H-C-C-H c2 H 11 ethane .. ALKENES Alkenes (e. ethene. The double bond in alkenes make them Ve.!J no • Unsaturate. Alkene (unsaturated) + hydrogen Alkane (saturated) . yel-t_oW flame l. --> + :: . Fathy Abdel Galli) .. + propene propane.dcU..g. ethane (sa. propene) are produced in large quantities in industry from the larger molecules in oil fractions by the process of cna~g.Chemistry IGCSE (Dr.c..d hydrocarbons undergo additior\ reactions: [A] Addition of hydrogen (hydrogenation) If ethene gas ·(unsaturated) in mixed with· hydrogen and is heated over a catalyst (nickel).tuni.IJ•.:Uan Jte. unsaturated (double bonds present) c 2 H6 saturated (all singie bonds present) Similarly. ...oin..... lzo... _... _...... It works ~ith any uMatukated moteeuf... The process is called ~dening o6 oilh... L e·.. . State another large scale use of hydrogen : ..e.. they are poiywua...........:tww.......Row would you show by a chemical test that olive oil is unsaturated 1 ........ . + ethene - H H C=C-/ ""' H/ bromine 1...... the red-orange colour of bromine goes colourless.... This raises the melting point. so the liquid oil becomes a solid fat .....--orange colourless colour + + ) C 3 ~Br 2 1.. Vegetable oil + Ni hydrogen catalyst > margarine Large amounts of hydrogen are used in industry for making margarine..Lne) ....2-dibromopropane Similarly..... Fathy Abdel Galil) Making Margarine The molecules of the vegetable oils contain several double bonds.....e bond.ted~ By reacting them with hydrogen and a catalyst (nickel).... ____ _ [B] Addition of bromine (Br 2) J\lkenes reactwith a solution of bromine in water (~q~eoub bll... -. Aqueous bromine (bromine ~ater) is used to test for a do~bf.. _.............. they are made - saturated... ____ ...-129- Chemistry !GCSE (Dr. .._ .. .... ethane adds chlorine to form dichluroethane....m~ga4Ute.2-dibromoethane --+ H H I I H-C-C-H I I Br-Br ""'H Br Br red. tphwU.lon.~!en~ nnd bt~m at high temperature (250°C].l.tyb. .-130- Chem.· . Fa thy Abdel Ga!il) Reaction with steam [Addition of water] EthanoL is formed in the reaction between.n~ . Shtc~ a wcd:e.U.cu.d [dehydrating agent].istry lGCSE (C] (Dr. ethene ·+ H..:t[on. th~ Jtwc.:Uon. to 6o1Ull dhe. catalyst Alkene water + Alcohol (steam) ).. {b) [D] Passing ethanol vapour over hot ~ o~de.f..M ~.-Zm-ln..ll ritaL~cu. Reaction with hydrogen chloride gas- H H + HCI ------.~d de..:t.hyciJw. Jt~v_e.c acJ.Cl H H chloroetnane ethene + HCt ._ H c. caf.t ) water (steam) /H C= C / '-.. L ~.:Uon ..t~ 6Mm illanof. H H + H-0-H H C2H4 ethanol -> I I H-C-G-0-H l l HH + H 0 2 > o > C H 0H 2 5 Similarly. caLLed hyciM. e.t~ hM . ---::> c 2H 4 + H 20 ethene Dehydration can be achieved by : (a-) Heating the ethanol with excUb concen:tluLt~d <>u. H 2 ptop<mol steam propene C H 0H 3 7 Generally. i + C3H6 ' -.b~w add~d to th~ doubL~ bond bt ill~n~.U. Jt~c. The.:ta. A catalyst is used (phosphoric acid].) I I I I H -'-C--C.a.ll moLe..ation a 6 wcd:e. .Pi H H H H H H ethene [monomer] 11. ..yJt. C=C I ~-~-t-6-d-d ... Poiymer: A macromolecule (large molecule) made by polymerising (joining together) ofmonomers. Monomer: A small molecule which =n be polymerised (joined together) to make a polymer. floor tiles.. I propene H.ty (ethene) I H ·H· H I H I H I H poly(ethene) [polymer] b-~iI I H H n is used to make plas.CI 'H I I I I I I I I I I I I _____. Fa thy Abdel Gatil) _ Addition polymerisation [Making plastics) F'o..taJtae.6 Pa. The polymerisation is done at high-temp~e and pressure in presence of a cata!.-131- Chemistry I GCSE E] (Dr.. n H/ c=c _. I -Ht l CHJ c_:_c n I. plastic bottles. H H H H H H chloroethene (vinyl chloride) poly( chloroethene) (PVC) Polykh..tic bags and plastic sheets.tym~. H H I H I C=C I H I H I I C=C + I H H I H l + l -->.tymvt-lb!Ltiott is the -process in vhich many small molecules (manam~) join together to ~ake a large molecule molecule) (macro- which is called-pa.. electric insulators and bottles. H n poly (propene) Paly(plwpenel is used to make plastic sheets.thene) known as PVC is used to make. I I I H H H.. HCIHCIHCl H. · . raincoa-ts and electrical wire insulators. c-c-c-c-c-c · · . . P..66ected by .a. PVC give~> o66 6wne.6 .ti.on pJr.tlvt woJull..n be Med a. They do no. Ug hte.cfty 1 .n-Winl>1 1>owey pau.JL. s.de cheap 1 and eM . beC1UL6e: 1• 2.t .a.de when 1t buJ!Ji6. \ Name H \ C 6H 5 poly(phenylethene) (polystyrene) H formula f "t I ~ n .a. i..UC-6 : good oJi bad ? i]QQ!!_t!Q{~ 1• Qu.. .b.cJ:.wa..ha..u.W c0t oiL wa.pe and c...!tm6u.c.own a.la.tlvr. .L>tie-6 ca..Uve. Many Me not a.L>. Fathy Ab9el Galil) . .tolt.. They Me d1661c.to any . When they bwr. e.ea.ta.teJt. a. Can be mou:tded.to d1opo1>e o6.tem.. 4.n.l Uwr.Ob.ot .y 1 1n o.dl.eJw. they aMen pltodu. 1 they Me non-:b1odegJUUia.ce ha.i.y made 2• 3.g.ga. Vo not conduct hea.toJU.be degltaded by rri.u. c.lL6e pou.o -Utbu1a.~> o6 hydltogen ch.u1.tonl> · do not Jtpt wh.Examples o{ other addition polymers Polymer Monomer formula/Name H I c=c I .•~ :coMo de .te1 1.t olt dec:tJU.cJtooJt. olr.ta.ta.a.Ul.en they Me . STYRENE (PHENYLETHENE) CN \ I c=c I \ Poly(acrylonitrile) +r 'tt c-c I H H pacKaging c-c c!H5 H I Uses H I H Synthetic fibre n ACRYLONITRILE F \ I c=c \ I F F poly{tetrafluroethene) or PTFE F tf-11 F F non-stick coating in frying pans n mRAFLUOROETHENE P.t gMel>: e. §~!!_t!Q~ P.Jt than me.o c.-te the env1Mnment.' .1n.n be cowwr.ed. .!tic bag!> and Ca.-132- Chemistry IGCSE (Dr.J1J!. . Ye.e. Fathy Abdel Gaiil) .tu.nt :to plte. Air lock allows carbon dioxide to escape.re con-:'·· yeast:. gas (C0 ) 2 .n:teJU.Makin<> ethanol by fermentation: . -:·: The process works best at Sugar solution (e..if pl(.) .f. ---. 6oJtme.i.6o.a. po. 6Jtom atc. add wUJ. vei:ted to ethanol and carbon d~ox~de gluco~_e) by· enzymes present ~n a. Ji.the. r~se· in temperature is observed Bubbles of a colourless.c. _.. k6:teJt :tha:t. The apparatus below can be used 1:0 ferment glucose • .~d. --1~::.an ortl.Hydration ofethene _ Addition of steam to ethene [obtained by the process of cracking] at'high temperature in pr~sence of a catalyst [see page 130] 2.. exotherm~c.ort. eL.f.t ..g.. e.::::::~ + .ng.i.o~g I 0% e.133- Chemistry IGCSE (Dr. ife.ng . e.. :the. hlrpolda. ethanol + carbon dioxide. allows fermentation under · anaerobic conditions jar yeast + glucose.M:t d..{.U.. butpre~ents air getting in.Jt 6Jtom.ve. the reaction is are also observed.aho.IU:ation ~s the process where sugars (e. be. I.d.v.water > What technique is used to concentrate the aqueous ethanol? .:tlutno. · o:th~e. __ Dur~ng s~nce a fermentation process.nt· aA..g. a .t.ETHANOL Making Ethanol for Industry -1. glucose) C6Hli 0 6 37~C.e.:::::::.tion c.tfutno. i.vv. b FeJutre..c.odu.i>:t -c..or~.i. (Dr.FathyAbdel Galil) . b.. Ethanol undergoes dehydra:tion and is converted into ethene when heated with. 2. Colourless liq11id. Spirits (whisky. In alcoholic drinks Uses of methanol (toxic) 1. Properties of Ethanol 1.many centuries. As a: solvent 2. concentrated sulphuric acid.p. brandy. Biotechnology Microorganisms have been used in some methods of food-making fcit . 3. Ethanol burns in air with a blue flame to form C02 and H 2 0 and heat · is given out. Beer is made by fermenting malt. Uses of Ethanol 1.} contain about 30% alcohol. 78°Cjrteutral to litmus. As a fuel 3. . One of the oldest kriown biotechnologies isferm(mtation. As a: fuel . Today these methods are often referred to as examples of 'biotechnology'. As a solvent 2.134- Chemistry IGCSE A laboratory experiment to demonstrate the fermentation: sugar solution andyeast -~ limewater Wine (contains about 10% ethanol) is made by fermenting grape juice. . .c............. .... ............ the colour changes from ••••••••••.. •... · .........'X~:. ....tha.. o.o~......... ....-~:!.noi. .... (from the Latin word for vinegar - 'acetum')......ed.c.......ge to..................hAomo.... I + 0 0 II H-C-C-0-H 2 I + H e..... Ethanol is o~ed to ethanoic acid... ~~g~1=~g=.i......... Formation of.......ng agent such as potah~ium d......... gltee:n........ . ......... Generally: alcohol [alkanol]' oxidation carboxylic ac~d Oxidation of methanol gives _. ... ......i...__: Vinegar is made by exposing ethanol to the air in the presence of' bacteria. ... On heating the colour changes from o.• to ....... ~ ~ H H-C-C-0-H I I H H Wta..... .d This is another example of 'biotechnolo'gy'.eth~noic acid....much more quickly-iri the laboratory by _heating it with an... . .... . Suggest a reason·why wine goes 'sour' when .i.........c... ..... when aqueous potassium dichromate (VI) is Jteduc...no. In other words...ed. Oxidation of propanol gives .n........... .. Ethanoic Acid from Ethanol a) £L~xi~~!::!:~:.._t:!!_~tmosEheric ~?... ........i....... ....135- Chemistry IGCSE Ethanoic acid > (Dr..te{VT} (adllified with sulphuric acid)... ~ _ b) Ethanol can b~ ox...........lta......Lon of --....U....Ui. Vinegar is a 5% solui:...left open in air·? .. Fa thy Abdel Galil) H Q' I II H-C-C-0-H I - H Ethano-ic acid is usually called acetic acid .. a.....c........d . •••••••••••••••••.i.....>litmus paper ).>lighted splint ethanol ethanoic acid no colour change no reaction .......ethanoic add + sodium hydroxide --* sodium ethanoate + water 1>............ ~~~~. The pH value of ethanoic acid is ................i..... Fa thy Abdel Galil) .. ········· .c............... Ethanoic acid (and all carboA-ylic acids) is a weak acid...c. a...i.. Examples_: 1>........... partially ionized in aqueous solution..d...........-£liH~=...alled ethanoate.••••••••••• .136- (Dr... Why? ..> sodium carbo-nate >potassium dichromate )..b juJ.....i.........ethanokacid + sodium carbonate --* sodium ethanoate + water + carbon dioxide However.......... It reacts with * Metals to form a salt + hydrogen * * Bases and alkalis to form a salt Carbonates to form a salt + water + water + carbon dioxide In each case the salt is:c...i. Ethano..> Differentiation between ethanol and ethanoic acid test )..... wea. the reaction of ethanoic acid is slower than of other acids such as hydrochloric acid or sulphuric acid... What is the colour produced on adding drop of universal indicator to ethanoic acid ? .c.:t Uke_ MCJ o.c.d. orange -7 green catches fire turns red effervescence -7 C02 no colour change does not catch fire ...!.c.Chemist1·y IGCSE .d .i...i...i. i. a.......e.....b a.....•........ : Et}w...no.. • ............theJt a.... ).k. ........ ..t etha..tphuh.p is produced by heating vegetable oils or animal fats with sodium hydroxide solution (i. When ethanoic acid + ethyl ethanoate + water ethanol ·•·.noa... j ester + water -·-:t carboxylic acid + alcohol Fats and Vegetable Oils Fats and oils are important constituents"of our· food.Ld in the presence of .tybib).£e is formed. .--the ester linkage 1/ H-C+C ·I \ H\ ' l H I H H H I 'o-+c-c-H + H2o \.oH:: H H H-C-C I H ·· .Lc. .. alka.c.Ou. Many fruits' smells are caused by esters... i..tha.- hy~d.. "· . · I I.0 ~ ~ .tha. They are e.t is heated with e.no.Ld as a catalyst..e contain the ester linkage [::-CQQ. ~ I 0 .. a. Fathy Abdel Gaiil) .6 ..tine Fats I oils +sodium hydroxide ~ -..no.e.. H +: H.Lc.137- Esters: Organic acids like ethanoic.6te. ~ 1..] Making Soap (Saponification) Soa. -.J I I Similarly: ethanoic acid + methanol ~ methyl ethanoate + ·water Ethylethanoate has a characteristic pleasant smell... Artificial flavouring are usually mixtures of esters. the ester ethy. The reverse reaction of esterification is called hydroly~is.. a.Jr. ester + water e..O-C-C-H \~ ...Chemistry IGCSE [Dr.c.acid react with alcohols to form compounds called eh£~ in a reaction co~~only called an organic acid + [carboxylic acid] ' alcohol ehte4i6ieation. soap + glycerol ...... o· --c=J. LQcto. 2- These compounds consist of carbon. The chemical name for ordinary sugar is . Fathy Abdel Galli) . hyd.6UCJl0. and honey. e.g._ the hydroge~ and oxygen atoms are present in the sariie ratio as in wa. is the sugar found in milk.Chemistry IGCSE (Dr.6e.o. 3- Sugars are carbohydrates which are soluble in water and taste ·sweet.Jw..6 a. and fructose occurs.o -c:::J. in fruit juices.ter.a.+ H2o starch (polymer) Ac. li (monomers) condensation polymerisation hydroly•h -o -c=J. CaJtboh!JdN:t.ucose molecul.6. with other sugars.• Glucose HO--Q-OH (a monomer) can be j6ined by in a l.on ]>o. glucose rolecules .Lucose molecules .o po.lymerisation. hydrogen and oxygen.tymeM : [ complex carbohydrates 1 Starch molecule consists of a long chain of g.te.!38- Carbohydrates 1- A family of energy foods including starch and sugars.U o6 c.JJJ..tu.tif.Starch ·can be hydrolysed into gl. starch : .es by boiling with dilute hydrochloric acid starch hydrochloric acid boiling I> glucose (simple sugars) .6e.ong chain to form starch (a polyl!ler) by condensad.JWohydJw.. This needs enzymes (biological catalysts). This-process can continue repeatedly tc produce long chain (i. . · ~ ·- amino ac~d l1 hydrolysis H 1 0 · II · H-N-c::J-C-N---~.. Proteins are broken down by hydrolysis into their ?mino acids.C~OH · ~~ amide linkage The linkage between the amino acids in a protein is called amide (peptide) linkage. This process. [5] .Chemistry lGCSE ....:-····· . Formation of a p.proteins can be hydrolysed into their amino acids by heating with dilute · acids (e.. macromolecule). Amino acids are the monomers from which proteins are made.e. .The products of the hydrolysis of proteins and carbohydrates can be separated and identified by chromatography. an amino group from one amino add reacts Vlith the carboxyl group from another (VIith elimination of water). occurs VI hen protein foods are digested.. ···I protein. )> )> These constituents of food can all be hydrolysed by boiling ·with acid or alkali. . !>-. amino acid condensation polyrner!satlon H ... \ II H-N-i=t-c<oH.lrt of protein chain : When proteins are formed. Fathy Abdel Galil) Proteins Proteins are natural macromolecules.139- (Dr.. are colourless so need spraying a locating agent to be seen on the chromatogram. The products. 0 . · linkage · consliluent of food protein product of hydrolysis - fat complex carbohydrate ~ Complete the table. HCL or HiS04). H 0 I II Ii. . )> In laboratory.: + ~-H~N-~C-OH .g. Polyamides..cl.g V>.. Polyamides (e. ~ H . .m{.am.g... s·yuthetit Macromolecule~ Polyesters Polyesters (e. c----[B.-···-c...R.. [2] .e.c.omo!.nd <>i:aJc... .N-0~N.tcofto...r is eliminated <1hen the monomer unlts link together . .. ll> What is the difference between addition polymerisq:tlon and condensation polymerisation? · ---------······-········--------------·-----·---··--···----·-----··----··--------··-----·-··--··:. H I . .c. nylon. na. H i (H-.C-N-: 0 -N)" ~ II \ .the. Polyesters are formed when HO- )( ? ..{_nu.... -Q. contain r:Uo-cl..dl.n a.. d H I _l_ .cJr.Jwmotecu..h P:W::l ..u.···..g.. a man-made fibre..· and cU.) are polymers which contain ester linkages.c-:mr· + : .dl.<. c~I22Ld:.II -- .ecu. .11 .Chemistry IGCSE (Dr.140- CONDENSATION POLYMERISATION Occurs when a small molecule such as ><ate.~. Nylon a. . combine· together.H...de UnfW.--·.nd i:. n examplV> of.· I .---.te.a. .--------~.P OH ..U combine together.e Pi!... CUte Me 0 .... Fathy Abdel Galli) . . ...n..ilc ma. ..tu!utt ma. and cUa. ~~ylene. syn.. are formed when a man~ made fibre) are polymers which clia.LV>.eJtyi. a. · . .. ...... 36 6...................3 3.....2 6.... 12 5...............1 3..1 1....................................4 3.5 6.. ...............................1 6.......................................................................... Syllabus aims and assessment .... Assessment at a glance ............ 7 6..1 Paper 4: Coursework 5....................3 6...... 5 3............6 Aims Assessment objectives Scheme of assessment Weightings Exam combinations Conventions 4........ 28 5...... 6 3.............. Curriculum content .......................2 3........... Introduction ..6 6..........Cambridge IGCSE Chemistry Syllabus code 0620 1...............8 Grade descriptions Periodic Table Notes for use in qualitative analysis Safety in the laboratory Glossary of terms Mathematical requirements Resource list Forms ·-·------·-·---·----------------------- .......... 2 1......2 1..3 Paper 6: Alternative to Practical 6...............................3 1.................... Practical assessment. Appendix .......................4 6...... 5 3...............2 Paper 5: Practical test 5.......4 Why choose Cambridge? Why choose Cambridge IGCSE Chemistry? Cambridge International Certificate of Education (ICE) How can I find out more? 2. uk/teachers. CIE invests constantly in improving its qualifications and services.1. They not only build understanding and knowledge required for progression.1 Why choose Cambridge? University of Cambridge International Examinations ICIEJ is the world's largest provider of international qualifications. What makes educators around the world choose Cambridge? Recognition Cambridge IGCSE is internationally recognised by schools. US Advanced Placement Programme and the International Baccalaureate (I B) Diploma. Not-for-profit. efficient administration of exams entry and excellent.org. Excellence in education Cambridge qualifications develop successful students. universities and employers as equivalent to UK GCSE. We offer a wide range of teacher materials to Centres. the Advanced International Certificate of Education IAICEJ. plus teacher training (online and face-to-face) and student support materials. a not-for-profit organisation and part of the University of Cambridge. Cambridge IGCSE is excellent preparation for A/AS Level.ul</recognition. Exams officers can trust in reliable. personal support from CIE Customer Services. Learn more at www. Learn more at www. part of the University of Cambridge CIE is part of Cambridge Assessment. 2 .cie. The needs of teachers and learners are at the core of what we do. Support CIE provides a world-class support service for teachers and exams officers. Around 1.cie.5 million students from 150 countries enter Cambridge examinations every year.org. but also learning and thinking skills that help students become independent learners and equip them for life. We draw upon education research in developing our qualifications. The Cambridge portfolio of IGCSE qualifications provides a solid foundation for higher level courses such as GCE A and AS Levels and the International Baccalaureate Diploma as well as excellent preparation for employment. skills which are useful in everyday life • learn how science is studied and practised.1. Science. It gives schools the opportunity to benefit from offering a broad and balanced curriculum by recognising the achievements of students who pass examinations in at least seven subjects. A wide range of IGCSE subjects is available and these are grouped into five curriculum areas. and take an informed interest in science and scientific developments • learn about the basic principles of Chemistry through a mix of theoretical and practical studies • develop an understanding of the scientific skills essential for further study at A Level.3 Cambridge International Certificate of Education (ICE) Cambridge ICE is the group award of the International General Certificate of Secondary Education (IGCSEI. Learn more about ICE at www. Chemistry falls into Group Ill. the Chemistry syllabus enables students to: • better understand the technological world in which they live. and become aware that the results of scientific research can have both good and bad effects on individuals. communities and the environment.org.cie. As well as a subject focus. 1. 3 .2 Why choose Cambridge IGCSE Chemistry? Cambridge IGCSE Chemistry is accepted by universities and employers as proof of essential chemistry knowledge and ability.uk/qualifications/academic/middlesec/ice. and one subject from each of the other subject groups. It requires the study of subjects drawn from the five different IGCSE subject groups. including two languages. uk. Learn more about the benefits of becoming a Cambridge Centre at www.org. please contact us at
[email protected] How can I find out more? If you are already a Cambridge Centre You can make entries for this qualification through your usual channels. CIE Direct. If you are not a Cambridge Centre You can find out how your organisation can become a Cambridge Centre.cie. 4 .org.uk. Email us at international@cie. If you have any queries. e.1.g. F or G. study the Core Curriculum only and are eligible for grades C to G. which comprises the Core and Supplement Curriculums. content and practical assessment sections for 2011 are indicated by black vertical lines on either side of the text. E.. Candidates expected to achieve grade Cor higher should study the Extended Curriculum. Candidates expected to achieve grades D.Cambridge IGCSE Chemistry Syllabus code 0620 Cambridge IGCSE Chemistry candidates are awarded grades ranging from A* to G. 5 . these candidates are eligible for all grades from A. Paper 4 Coursework weighted at 20% of total available marks Paper 5 1 hour 15 minutes Practical test weighted at 20% of total available marks 1 hour Paper 6 Alternative to Practical paper weighted at 20% of total available marks Alterations in the syllabus assessment. to G. All candidates must enter for three papers. to enable candidates to acquire sufficient understanding and knowledge to 3. technological. The aims are: 1. ethical and cultural influences and limitations • the applications of science may be both beneficial and detrimental to the individual. correctly and rigorously applied. able to take an informed interest in scientific matters • recognise both the usefulness and the limitations of scientific method. the community and the environment • science transcends national boundaries and that the language of science. to develop attitudes relevant to Chemistry such as • concern for accuracy and precision • objectivity • integrity • enquiry • initiative • inventiveness 5.1 Aims The aims of the syllabus listed below describe the educational purposes of this examination.3. • become confident citizens in a technological world. as a result of co-operative activities of groups and individuals • the study and practice of science are subject to social. The aims of the syllabus are the same for all students and are not listed in order of priority. and continue to do so. economic. whether or not they go on to study science beyond this level 2. 6 . is universal. and appreciate its applicability in other disciplines and in everyday life • be suitably prepared for studies beyond IGCSE in pure sciences. through well-designed studies of experimental and practical science. to provide a worthwhile educational experience for all candidates. to stimulate interest in the environment and caring for it 6. in applied sciences or in sciencedependent vocational courses to develop abilities and skills that • are relevant to the study and practice of Chemistry • are useful in everyday life • encourage efficient and safe practice • encourage effective communication 4. to promote an awareness that • scientific theories and methods have developed. report trends and draw inferences 5. including techniques of operation and aspects of safety 4. scientific instruments and apparatus. explain or outline (see Glossary ofTerms). scientific vocabulary. laws. economic and environmental implications. quantities and units) 3. terminology and conventions (including symbols. scientific and technological applications with their social. graphical and numerical). to 1. manipulate numerical and other data 4. select. B: Handling information and problem solving Students should be able. Candidates will also be asked questions which require them to apply this material to unfamiliar contexts and to apply knowledge from one area of the syllabus to knowledge of a different syllabus area. 7 . use information to identify patterns. make predictions and hypotheses 7. describe. solve problems. scientific quantities and their determination 5. symbolic. patterns and relationships 6. A: Knowledge with understanding Students should be able to demonstrate knowledge and understanding in relation to 1.e. facts. Questions testing these objectives will often begin with one of the following words: define. translate information from one form to another 3. definitions. concepts and theories 2. locate. scientific phenomena. Curriculum content defines the factual material that candidates may be required to recall and explain.2 Assessment objectives The three assessment objectives in Cambridge lGCSE Chemistry are: -- A Knowledge with understanding B Handling information and problem solving G Experimental skills and investigations A description of each assessment objective follows. organise and present information from a variety of sources 2. in words or using other written forms of presentation (i. including some of a quantitative nature. present reasoned explanations for phenomena. state.3. should be entered for Paper 3. All candidates must take a practical paper. evaluate methods and suggest possible improvements (including the selection of techniques. 8 . Questions testing these skills will often begin with one of the following words: predict. Candidates who have only studied the Core curriculum. calculate or determine. should normally be entered for Paper 2. and who are expected to achieve a grade C or above.3 Scheme of assessment All candidates must enter for three papers: Paper 1. in a logical. plan investigations.Questions testing these skills may be based on information that is unfamiliar to candidates. apparatus and materials (including following a sequence of instructions where appropriate) 2.) ·C: Experimental skills and investigations Students should be able to 1. or who are expected to achieve a grade D or below. make and record observations. Candidates who have studied the Extended curriculum. 3. suggest. know how to use techniques. measurements and estimates 3. 5 or 6. interpret and evaluate experimental observations and data 4. apparatus and materials). either Paper 2 or Paper 3. or Paper 6 (Alternative to Practical). deductive way. requiring them to apply the principles and concepts from the syllabus to a new situation. chosen from: Paper 4 (Coursework). and one from Papers 4. (See the Glossary o!Terms. Paper 5 (Practical Test). Questions will be based on the Core curriculum and will be of a difficulty appropriate to grades C to G. This paper will be weighted at 30% of the final total available marks. This paper will test skills mainly in Assessment objectives A and B. Paper 2 1 hour 15 minutes Paper 3 1 hour 15 minutes Written paper consisting of short-answer and structured questions. Written paper designed to test familiarity with laboratory based procedures. This paper will be weighted at 50% of the final total available ~1arks. Questiolrs will be based on the Core curriculum and will be of a difficulty appropriate to grades C to G. 1 hour 15 minutes Paper 4* Paper 5* Coursework Practical Test Alternative to Practical School-based assessment of practical skills. 80 marks 80 marks This paper will be weighted at 50% of the final total available marks. Questions will test skills mainly in Assessment objectives A and B.Paper 1 45 minutes A multiple-choice paper consisting of 40 items of the four-choice type. Written paper consisting of short-answer and structured questions. A quarter of the marks available will be based on Core material and the remainder on the Supplement.** Questions covering experimental and observational skills. weighted at 20% of the final total available marks weighted at 20% of the final total available marks weighted at 20% of the final total available marks 9 Paper 6* 1 hour . Questions will be based on the Extended curriculum and will be of a difficulty appropriate to the higher grades. Questions will test skills mainly in Assessment objectives A and B. ** Teachers may not undertake school-based assessment without the written approval of CIE.countries where there is a need. practical. experimental and investigative skills} and for knowledge and understanding. 3. problem solving. so that the aims of the syllabus may be met. Candidates will not be required to use knowledge outside the Core curriculum.* This component tests appropriate skills in assessment Objective C.4 Weightings A: Knowledge with understanding 50% (not more than 25% recall} B: Handling information and problem solving 30% C: Experimental skills and investigations 20% Teachers should take note that there is an equal weighting of 50% for skills (including handling information. CIE offers schools in-service training in the form of occasional faceto-face courses held in. avail~ble from CIE Publications. Teachers' schemes of work and the sequence of learning activities should reflect this balance. A: Knowledge with understanding 25-30 48-52 0 47-54 B: Handling information and problem solving 10-15 27-32 0 26-33 0 0 40 20 C: Experimental skills and investigations 10 . This is only given to teachers who satisfy CIE requirements concerning moderation and who have to undergone special training in assessment. and also through the CourseworkTraining Handbook. and the candidates fully prepared for the assessment. Symbols and Systematics: The ASE Companion to 16-19 Science (2000). 3. In particular.5 Exam combinations Candidates can combine this syllabus in an exam session with any other CIE syllabus.g. Cambridge International Level 1/Level 2 Certificates and 0 Level syllabuses are at the same level.nce: • 0654 IGCSE Co-ordinated Sciences (Double Award) • 5124 0 Level Science (Physics. except: • syllabuses with the same title at the same level • 0652 IGCSE Physical Science • 0653 IGCSE Combined Sde. the following documents. dm' will be used in place of I or litre.6 Conventions (e. 11 . terminology and nomenclature) Syllabuses and question papers conform with generally accepted international practice. published in the UK. should be used as guidelines: Reports produced by the Association for Science Education lASE): 51 Units. Symbols and Abbreviations (1981) Chemical Nomenclature. Symbols and Terminology for use in School Science (1985) Signs. signs. symbols. Biology) • 5129 0 Level Combined Science • 5130 0 Level Additional Combined Science Please note that IGCSE. Litre/dm' To avoid any confusion concerning the symbol for litre.3. Chemistry) • 5126 0 Level Science (Chemistry. Signs. CIE provides schemes of work. which includes both the Core and the Supplement. Core Supplement • Describe the states of matter and explain their interconversion in terms of the kinetic particle theory • • Describe and explain diffusion • Describe evidence for the movement of particles in gases and liquids (a treatment of Brownian motion is not required) Describe dependence of ra<e of diffusion on molecular mass (treated qualitatively) 2.. such as the availability and cost of raw materials and .g. mass and volume. It is important that. e.1 Measurement Core • Name appropriate apparatus for the measurement of time. including the use of R. In particular. foodstuffs and drugs Outline how chromatography techniques can be applied to colourless substances by exposing chromatograms to substances called locating agents (knowledge of specific locating agents is not required) 12 . throughout this course. pipettes and measuring cylinders 2. and to the natural and man-made worlds. attention should be drawn to: • the finite life of the world's resources and the need for recycling and conservation • economic considerations in the chemical industry.2 (a) Criteria of purity Core Supplement • Describe paper chromatography • • Interpret simple chromatograms Interpret simple chromatograms. teachers should make candidates aware of the relevance of the concepts studied to everyday life. which can be found on the CIETeacher Support website. Specific content has been limited in order to encourage this approach.The Curriculum content below is a guide to the areas on which candidates are assessed. energy • the importance of chemicals in both industry and everyday life. temperature. Candidates may follow the Core curriculum only or they may follow the Extended curriculum. and to allow flexibility in the design of teaching programmes. values • Identify substances and assess their purity from melting point and boiling point information • • Understand the importance of purity in substances in everyday life. including burettes. given information about the substances involved 3.2. (Refer to the fractional distillation of crude oil in sectioo 14.6. as shown in the Appendix. crystallisation.) • Suggest suitable purification techniques.) Note: a copy of the Periodic Table.1 Atomic structure and the Periodic Table Core • State the relative charges and approximate relative masses of protons. filtration. neutrons and electrons • Define proton number and nucleon number • Use proton number and the simple structure of atoms to explain the basis of the Periodic Table (see section 9).2 flnd products of fermentation in section 14.2 (b) Methods of purification Core • Describe methods of purification by the use of a suitable solvent. distillation (including use of fractionating column). will be available in Papers 1. 2 and 3) 13 . with special reference to the elements of proton number 1 to 20 • Define isotopes • State the two types of isotopes as being radioactive and non-radioactive • State one medical and one industrial use of radioactive isotopes • Describe the build-up of electrons in 'shells' and understand the significance of the noble gas electronic structures and of valency electrons (the ideas of the distribution of electrons in s and p orbitals and in d block elements are not required. 3.2 Bonding: the structure of matter Core • Describe the differences between elements . mixtures and compounds, and between metals and non-metals • Describe an alloy, such as brass, as a mixture of metal with other elements a- 3.2 (a) Ions and ionic bonds Core • • Describe the formation of ions by electron loss or gain Describe the formation of ionic bonds between elements from Groups I and VII 3.2 (b) lvlolecules and covalent bonds Core Supple.ment • Describe the formation of single covalent bonds in H,. C~ . H,O, CH, and HC1 as the sharing of pairs of electrons leading to the noble gas configuration • Describe the formation of ionic bonds between metallic and non-metallic elements • Describe the differences in volatility, solubility and electrical conductivity between ionic and covalent compounds • Describe the lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions 3.2 (c) lvlacromolecules Core Supplement • Describe the giant covalent structures of graphite and diamond • • Relate their structures to the use of graphite as a lubricant and of diamond in cutting Describe the electron arrangement in more complex covalent molecules such as N 2, C,H,. CH,OH and CO, • Describe the macromolecular structure of silicon(JV) oxide (silicon dioxide) 3.2 (d) lvletallic bonding Supplement ----------·---- ·------------------- 14 • Describe the similarity in properties between diamond and silicon(IV) oxide. related to their structures • Describe metallic bonding as a lattice of positive ions in a 'sea of electrons' and use this to describe the electrical conductivity and malleability of metals --~--~-------------- Core Supplement • Use the symbols of the elements and write the formulae of simple compounds • • Deduce the formula of a simple compound from the relative numbers of atoms present Determine the formula of an ionic compound from the charges on the ions .. present • Deduce the formula of a simple compound from a model or a diagrammatic representation Construct equations with state symbols, including ionic equations • Deduce the balanced equation for a chemical reaction, given relevant information • • Construct word equations and simple balanced chemical equations • Define relative atomic mass, A, • Define relative molecular mass, M,, as the sum of the relative atomic masses (relative formula mass or M, will be used for ionic compounds) (Calculations involving reacting masses in simple proportions may be set. Calculations will not involve the mole concept.) 4.1 The mole concept Supplement • Define the mole and the Avogadro constant 15 • Use the molar gas volume, taken as 24 dm 3 at room temperature and pressure • Calculate stoichiometric reacting masses and volumes of gases and solutions, solution concentrations expressed in g/dm' and mol/dm'. (Calculations involving the idea of limiting reactants may be set. Questions on the gas laws and the conversion of gaseous volumes to different temperatures and pressures will not be set.) • Calculate empirical formulae and molecular formulae • Calculate % yield and % purity Core Supplement • • Relate the products of electrolysis to the electrolyte and electrodes used, exempJified by the specific examples in the Core together with aqueous copper(ll) sulfate using carbon electrodes and using copper electrodes (as used in the refining of copper) Describe the electrode products in the electrolysis of: molten lead(! I) bromide concentrated hydrochloric acid concentrated aqueous sodium chloride between inert electrodes (platinum or carbon) • State the general principle that metals or hydrogen are formed at the negative electrode (cathode). and that non-metals (other than hydrogen) are formed at the positive electrode (anode) • Describe electrolysis in terms of the ions present and reactions at the electrodes in the examples given • Predict the products of the electrolysis of a specified binary compound in the molten state • • Describe the electroplating of metals Predict the products of electrolysis of a specified halide in dilute or concentrated aqueous solution • Name the uses of electroplating • Describe, in outline, the manufacture of • Describe the reasons for the use of copper and (steel-cored) aluminium in cables, and why plastics and ceramics are used as insulators aluminium from pure aluminium oxide in molten cryolite chlorine and sodium hydroxide from concentrated aqueous sodium chloride (Starting materials and essential conditions should be given but not technical details or diagrams.) - 6. 1 Energetics of a reaction Core • Supplement Describe the meaning of exothermic and • endothermic reactions 16 Describe bond breaking as endothermic and bond forming as exothermic mines) • 17 Describe and explain the effects of temperature and concentration in terms of collisions between reacting particles • Describe the effect of light on the speed of reactions • Describe the use of silver salts in photography as a process of reduction of silver ions to silver. as a 7. catalysts (including enzymes) and temperature on the speeds of reactions • Devise a suitable method for investigating the effect of a given variable on the speed of a reaction • Describe a practical method for investigating the speed of a reaction involving gas evolution • Interpret data obtained from experiments concerned with speed of reaction • Describe the application of the above factors to the danger of explosive combustion with fine powders (e.1 Speed of reaction Core Supplement • Describe the effect of concentration. particle size. and photosynthesis as the reaction between carbon dioxide and water in the presence of chlorophyll and sunlight (energy) to produce glucose .3.2 Production of energy Core Supplement • Describe the production of electrical energy from simple cells.6.) • Describe the use of hydrogen as a potential fuel reacting with oxygen to generate electricity in a fuel cell (details of the construction and operation of a fuel cell are not required) Describe the production of heat energy by burning fuels • Describe hydrogen as a fuel o Describe radioactive isotopes. (This should be linked with tbe·reactivity series in section 10. flour mills) and gases (e.g. two electrodes in an electrolyte.e.2 and redox in section 7.g. such as source of energy 235 U. i. 2 Types of oxides Core Supplement • • Classify oxides as either acidic or basic. limited to aqueous solutions on litmus • Describe the characteristic properties of bases as Define ac1ds and bases in terms of • reactions with acids and with ammonium salts and Describe the meaning of weak and strong acids and bases effect on litmus • Describe neutrality and relative acidity and alkalinity in terms of pH (whole numbers only) measured using Universal Indicator paper • Describe and explain the importance of controlling acidity in soil 8. dichromate(Vl) . manganate(VIl).1 The characteristic properties of acids and bases Core Supplement • • Describe the characteristic properties of acids as reactions with metals. is not required. e. and potassium iodide. bases. carbonates and effect proton transfer.) Define redox in terms of electron transfer • Identify redox reactions by changes in oxidation state and by the colour changes involved when using acidified potassium manganate(VIl). Concept of equilibrium is not required.' 7.g. related to Further classify other oxides as neutral or amphoteric metallic and non-metallic character 18 . (Oxidation state limited to its use to name ions.2 Reversible reactions Core Supplement • • Describe the idea that some chemical reactions can be reversed by changing the reaction conditions Predict the effect of changing the conditions (temperature and pressure) on other reversible reactions (Limited to the effects of heat on hydrated salts. (Recall of equations involving KMnO. copper([]). iron(! I). iron(III).) 8.3 Redox Supplement Core Define oxidation and reduction in terms of oxygen • • loss/gain.) • Concept of equilibrium- 7. sulfate (by reaction under acidic conditions with aqueous barium ions) gases: ammonia (using damp red litmus paper).4 Identification of ions and gases Core • Describe the following tests to identify: aqueous cations: aluminium.2(b) and the reactions specified in section 8. iron(lll) and zinc (using aqueous sodium hydroxide and aqueous ammonia as appropriate) (Formulae of complex ions are not required. copper(!!). carbon dioxide (using limewater). oxygen (using a glowing splint). chloride (by reaction under acidic conditions with aqueous silver nitrate). hydrogen (using lighted splint).3 Preparation of salts Core Supplement • • Describe the preparation of insoluble salts by precipitation • Suggest a method of making a given salt from suitable starting material. nitrate (by reduction with aluminium). separation and purification of salts as examples of some of the techniques specified in section 2.8. 19 .) anions: carbonate (by reaction with dilute acid and then limewater). iodide (by reaction under acidic conditions with aqueous silver nitrate). ammonium. chlorine (using damp litmus paper). calcium. iron(fl).1 8. given appropriate information Describe the preparation. given information about the elements concerned 9.e. given data. helium for filling balloons ---~·------ 20 . and state their reaction with other halide ions Predict the properties of other elements in Group VII. argon in lamps. and which. given data where appropriate • Identify trends in other Groups. high melting points and forming coloured compounds.4 Noble gases Core • Describe the noble gases as being unreactive Describe the uses of the noble gases in providing an inert atmosphere. where appropriate • Describe chlorine.3 Transition elements Core • Describe the transition elements as a collection of metals having high densities. often act as catalysts fi. i. as elements and compounds. sodium and potassium in Group I as a collection of relatively soft metals showing a trend in melting point. number of valency electrons and metallic/non-metallic character 9.2 Group properties Supplement Core • Describe lithium.1 Periodic trends Core Supplement • • Describe the change from metallic to non-metallic character across a period Describe the relationship between Group number. density and reaction with water • Predict the properties of other elements in Group I.Core • Describe the Periodic Table as a method of classifying elements and its use to predict properties of elements 9. bromine and iodine in Group VII as a collection of diatomic non-metals showing a trend in colour. illustrated by its reaction. the extraction of zinc from zinc blende .3 (a) Extraction of metals Core Supplement • Describe the ease in obtaining metals from their ores by relating the elements to the reactivity series • • Name the main ore of aluminium as bauxite (see section 5) Describe the essential reactions in the extraction of iron from hematite • Describe the conversion of iron into steel using basic oxides and oxygen 21 describe in outline.2. by reference to the reactions. calcium. Reactivity series Core Supplement Place in order of reactivity: potassium. of the metals with • water or steam Describe the reactivity series as related to the tendency of a metal to form its positive ion.1 Properties of metals Core Describe the general physical and chemical properties of metals Explain why metals are often used in the form of alloys Identify representations of alloys from diagrams of structure • 10. (hydrogen) and copper.10. with the aqueous ions dilute hydrochloric acid the oxides and the reduction of their oxides with carbon of the other listed metals • • Describe the action of heat on the hydroxides and nitrates of the listed metals • Account for the apparent unreactivity of aluminium in terms of the oxide layer which adheres to the metal Deduce an order of reactivity from a given set of experimental results 10. if any. magnesium. if any. iron. zinc. sodium. oxides of nitrogen and lead compounds • State the source of each of these pollutants: carbon monoxide from the incomplete combustion of carbon-containing substances sulfur dioxide from the combustion of fossil fuels which contain sulfur compounds (leading to 'acid rain'. 20% oxygen and the remainder as being a mixture of noble gases. the purification of the water supply in terms of filtration and chlorination • Name some of the uses of water in industry and in the home • Describe'the composition of clean air as being approximately 79% nitrogen.10. in outline. water vapour and carbon dioxide • Name the common pollutants in the air as being carbon monoxide.see section 13) oxides of nitrogen from car exhausts • • Describe and explain the presence of oxides of nitrogen in car exhausts and their catalytic removal • Describe the separation of oxygen and nitrogen from liquid air by fractional State the adverse effect of common pollutants on buildings and on health distillation 22 .3 (b) Uses of metals Core Supplement • • Name the uses of aluminium: in the manufacture of aircraft because of its strength and for making brass and low density • in food containers because of its resistance to corrosion • Describe the idea of changing the properties of iron by the controlled use of additives to form steel alloys • Name the uses of mild steel (car bodies and machinery) and stainless steel (chemical plant and cutlery) Name the uses of zinc for galvanising Name the uses of copper related to its properties (electrical wiring and in cooking utensils) Supplement Core • Describe a chemical test for water • Describe. sulfur dioxide. hydrocarbons or steam and air • Describe the carbon cycle.e. to include the processes of combustion. in simple terms.• Describe methods of rust prevention. respiration and photosynthesis as a product of complete combustion of carboncontaining substances as a product of respiration as a product of the reaction between an acid and a carbonate • State the sources of methane. i. phosphorus. including essential conditions • Describe the properties of dilute sulfuric acid as a typical acid . including decomposition of vegetation and waste gases from digestion in animals Supplement 23 • Name some sources of sulfur • Name the use of sulfur in the manufacture of sulfuric acid • Name the uses of sulfur dioxide as a bleach in the manufacture of wood pulp for paper and as a food preservative (by killing bacteria) • Describe the manufacture of sulfuric acid by the Contact process.and potassium-containing fertilisers • Describe the displacement of ammonia from its salts • State that carbon dioxide and methane are greenhouse gases and may contribute to climate change • Describe the formation of carbon dioxide: • Describe sacrificial protection in terms of the reactivity series of metals and galvanising as a method of rust prevention • Describe the essential conditions for the manufacture of ammonia by the Haber process including the sources of the hydrogen and nitrogen. specifically paint and other coatings to exclude oxygen • Describe the need for nitrogen-. 4-14. waxes and polishes bitumen for making roads 24 Name and draw the structures of the unbranched alkanes. given a chemical name ending in -ane. natural gas and petroleum Name methane as the main constituent of natural gas • Describe petroleum as a mixture of hydrocarbons and its separation into useful fractions by fractional distillation Name the uses of the fractions as: refinery gas for bottled gas for heating and cooking gasoline fraction for fuel (petrol) in cars naphtha fraction for making chemicals kerosene/paraffin fraction for jet fuel diesel oil/gas oil for fuel in diesel engines fuel oil fraction for fuel for ships and home heating systems lubricating fraction for lubricants. ethanol. or a molecular structure 14. ethane. -ene.2 Fuels Core • Name the fuels coal.g.Core • Describe the manufacture of lime (calcium oxide) from calcium carbonate (limestone) in terms of the chemical reactions involved • Name some uses of lime and slaked lime as in treating acidic soil and neutral ising acidic industrial waste products. alkenes (not cistrans). or -oic acid.1 Names of compounds Supplement Core • Name and draw the structures of methane. flue gas desulfurisation • Name the uses of calcium carbonate in the manufacture of iron and of cement 14. -ol.6 • State the type of compound present. alcohols and acids containing up to four carbon atoms per molecule . ethanoic acid and the products of the reactions stated in sections 14. e. hydrogen and steam .3 Homologous series Core Supplement • • Describe the general characteristics of an homologous series • Describe and identify structural Describe the concept of homologous series as a 'family' of similar compounds with similar properties due to the presence of the same functional group isomerism 14.14.4 Alkanes Core Supplement • Describe the properties of alkanes (exemplified by methane) as being generally unreactive.6 Alcohols Core • Describe the formation of ethanol by fermentation and by the catalytic addition of steam to ethene • Describe the properties of ethanol in terms of burning • Name the uses of ethanol as a solvent and as a fuel 25 Describe the properties of alkenes in terms of addition reactions with bromine.5 Alkenes Core Supplement • Describe the manufacture of alkenes and of hydrogen by cracking • • Distinguish between saturated and unsaturated hydrocarbons • - from molecular structures - by reaction with aqueous bromine Describe the formation of poly(ethene) as an example of addition polymerisation of monomer units 14. except in terms of burning • • Describe the bonding in alkanes Describe substitution reactions of alkanes with chlorine 14. 14. 0 0 I 0 I 0 I I -c~c-~-[]-~-c~c-~-[]-~-c~ H H H H and the structure of Terylene as: 0 0 0 0 -~~~-o-[]-o-~~~-o-[]-o(Details of manufacture and mechanisms of these polymerisations are not required.) 26 .8 Macromolecules Supplement • Describe the formation of ethanoic acid by the oxidation of ethanol by fermentation and with acidified potassium manganate(VII) • Describe ethanoic acid as a typical weak acid • Describe the reaction of ethanoic acid with ethanol to give an ester (ethyl ethanoatel Supplement • 14.7 Acids 14.. different macromolecules having different units and/or different linkages Supplement • Name some typical uses of plastics and of man-made fibres • Describe the pollution problems caused by non-biodegradable plastics • Deduce the structure of the polymer product from a given alkene and vice versa • Describe the formation of nylon (a polyamide) and Terylene (a polyester) by condensation polymerisation. Describe macromolecules in terms of large molecules built up from small units (mononomers). the structure of nylon being represented as: 0 I .8 (al Synthetic polymers . starch) to give simple sugars • Describe the fermentation of simple sugars to produce ethanol (and carbon dioxide) (Candidates will not be expected to give the molecular formulae of sugars.g. fats and carbohydrates as the main constituents of food • Describe proteins as possessing the same (amide) linkages as nylon but with different units Describe the structure of proteins as: H 0 R H 0 I I I I I -N-C-C-N-C-C-N-C-C1 I I I R H 0 R • Describe the hydrolysis of proteins to amino acids (Structures and names are not required.) • Describe fats as esters possessing the same linkage as Tery!ene but with different units • Describe soap as a product of hydrolysis of fats • Describe complex carbohydrates in terms of a large number of sugar units.14. the usefulness of chromatography in separating and identifying the product of hydrolysis of carbohydrates and proteins -----~ 27 . considered as Ho-D-oH. e.g.) • Describe. joined together by condensation polymerisation. in outline.8 (b) Natural macromolecules Supplement • Name proteins. -·--~- -o-D-o-D-o-D-o- • Describe the acid hydrolysis of complex carbohydrates (e. or more than one step if structured help is given • identify a pattern or trend where only minor manipulation of data is needed • recognise which of two given hypotheses explains a set of facts or data A Grade A candidate will be able to: A Grade C candidate will be able to: A Grade F candidate will be able to: 36 . or find facts to support a hypothesis • link facts to situations not specified in the syllabus • describe the correct procedure(s) for a multi-stage operation • select a range of information frorn a given source and present it in a clear logical form • identify patterns or trends in given information • solve a problem involving more than one step. • relate facts to principles and theories and vice versa • state why particular techniques are preferred for a procedure or operation • select and collate information from a number of sources and present it in a clear logical form • solve problems in situations which may involve a wide range of variables • process data from a number of sources to identify any patterns or trends • generate a hypothesis to explain facts. but with a limited range of variables • generate a hypothesis to explain a given set of facts or data • recall facts contained in the syllabus • indicate the correct procedure for a single operation • select and present a single piece of information from a given source • solve a problem involving one step. I The scheme of assessment is intended to encourage positive achievement by all candidates.1 Grade descriptions .6. • relate facts to principles and theories and vice versa • state why particular techniques are preferred for a procedure or operation • select and collate information from a number of sources and present it in a clear logical form o solve problems in situations which may involve a wide range of variables • process data from a number of sources to identify any patterns or trends o generate a hypothesis to explain facts. but with a limited range of variables • generate a hypothesis to explain a given set of facts or data • • • • recall facts contained in the syllabus • • indicate the correct procedure for a single operation select and present a single piece of information from a given source solve a problem involving one step. or find facts to support a hypothesis • • • link facts to situations not specified in the syllabus A Grade A candidate will be able to: . A Grade C candidate will be able to: A Grade F candidate will be able to: describe the correct procedure(s) for a multi-stage operation select a range of information from a given source and present it in a clear logical form • identify patterns or trends in given information • solve a problem involving more than one step.1 Grade descriptions The scheme of assessment is intended to encourage positive achievement by all candidates. or more than one step if structured help is given identify a pattern or trend where only minor manipulation of data is needed recognise which of two given hypotheses explains a set of facts or data ~-~-------·--·--~----------~----------- 36 --- .6.. Tests for aqueous cations aluminium IAZ'•I white ppt. solub[e in excess. or very slight white ppt. iodide WI lin solution} acidify with dilute nitric acid. then add aqueous silver nitrate white ppt. insoluble in excess no ppt.J ammonia produced on warming calcium (Ca''l white ppt. warm carefully ammonia produced sulfate (SO .... insoluble in excess light blue ppt.3 Notes for use in qualitative analysis Tests for anions carbonate (C0 3''1 add dilute acid effervescence. insoluble in excess green ppt. carbon dioxide produced chloride (CrJ (in solution} acidify with dilute nitric acid. giving a dark blue solution green ppt.. then add aqueous silver nitrate yellow ppt. giving a colourless solution ammonia (NH 3) turns damp red litmus paper blue carbon dioxide (C0 2) turns limewater milky chlorine (CI.. insoluble in excess red-brown ppt. soluble in excess.. light blue ppt.1 relights a glowing splint 38 white ppt. giving a colourless solution white ppt.) bleaches damp litmus paper hydrogen 'pops' with a lighted splint oxygen 10.. insoluble in excess . soluble in excess giving a colourless solution ammonium (NH. soluble in excess. nitrate (N0 3·1 [in solution} add aqueous sodium hydroxide.'·1 [in solution} acidify.. then add aqueous barium nitrate white ppt... then aluminium foil. insoluble in excess white ppt. insoluble in excess red-brown ppt.6.. org/networks/learnnet/Safety. Associations CLEAPSS is an advisory service providing support in practical science and technology. 2006 Topics in Safety. 2001 CLEAPSS Laboratory Handbook.htm.uk/safety.ac. 1997 Hazardous Chemicals.org. publications and regulations. ncbe.uk/SI/si2002/20022677. SSERC. ASE. a brief guide may be found at http:/ /www.html Publications Safeguards in the School Laboratory. SSERC. Further information can be found in the following UK associations. HMSO.htm http://www. 3" Edition. An interactive manual for science education. 2005 update of 1995 edition (available to CLEAPSS members only) Safety in Science Education.6. 1996 Hazardous Chemicals Manual.html http:/ /www. 2002 (CD) Ul< Regulations Control of Substances Hazardous to Health Regulations (COSH H) 2002 http:/ /www.microbiologyonline.opsi.hse. 11 <h Edition.chemsoc.pdf 39 . International schools and post-16 colleges can apply for associate membership which includes access to the CLEAPSS publications listed below http:/ /www. updated 2005 (available to CLEAPSS members only) CLEAPSS Hazcards.uk/NCBE/SAFETYI menu.4 Safety in the laboratory Responsibility for safety matters rests with Centres.cleapss.gov.uk{pubns/indg136.uk Websites http:/ /www. websites.gov. ASE. DIES.org. primarily for UK schools.reading. 4. Predict implies that the candidate is not expected to produce the required answer by recall but by making a logical connection between other pieces of information. I is intended literally. describe should be interpreted more generally (i. or the necessary reasoning is to be included in the answer. especially where two or more terms are included in the question. e. or to imply that candidates are expected to apply their general knowledge of the subject to a 'novel' situation. 5. In the former instance. etc. in Chemistry. i.. measure. Where a given number of points is specified this should not be exceeded. either to imply that there is no unique answer (e. What do you understand by/What is meant by (the term lsi . one that may be formally 'not in the syllabus'. a numerical answer that can readily be obtained 'by inspection'). generally each of one word. 9.g.. as may state and explain. 8. In other contexts. State implies a concise answer with little or no supporting argument (e. determine.e. Predict also implies a concise answer with no supporting statement required. Outline implies brevity (i. Describe and explain may be coupled. Deduce is used in a similar way to predict except that some supporting statement is required. 11. the term usually implies that the answer should include reference to (visual) observations associated with the phenomena. The glossary has been deliberately kept brief.g. two or more substances may satisfy the given conditions describing an 'unknown'). only a formal statement or equivalent paraphrase being required. It is often used with reference either to particular phenomena or to particular experiments.rnany data response and problem solving questions are of this type. I normally implies that a definition should be given. restricting the answer to giving essentials). Discuss requires the candidate to give a critical account of the points involved in the topic. but it is neither exhaustive nor definitive. reference to a law or principle. 6. 1. Define (the term(s) .6. Describe requires the candidate to state in words (using diagrams where appropriate) the main points of the topic. 40 . Find is a general term that may variously be interpreted as calculate. in part. together with some relevant comment on the significance or context of the term(s) concerned. 3. 7. Such information may be wholly given in the question or may depend on answers extracted in an earlier part of the question. 12..e.5 Glossary of terms used in science papers The glossary (which is relevant only to Science subjects) will prove helpful to candidates as a guide.g. Explain may imply reasoning or some reference to theory. The amount of supplementary comment intended should be interpreted in the light of the indicated mark value. Suggest is used in two main contexts. on its context. the candidate has greater discretion about the nature and the organisation of the material to be included in the answer). with no elaboration.e. 10. not only with respect to the number of terms included. depending on the context. but also to the descriptions of their meanings. List requires a number of points. Candidates should appreciate that the meaning of a term must depend. 2. g. some quantitative aspects may be looked for (e. calculation. Measure implies that the quantity concerned can be directly obtained from a suitable measuring instrument (e. using a balance). but candidates should be aware that. substituting measured or known values of other quantities into a standard formula e. length. passing through the origin. nevertheless. ·- 16. sketch implies that simple. when applied to graph work. working should be shown. depending on the context. having an intercept). Determine often implies that the quantity concerned cannot be measured directly but is obtained by. care should be taken over proportions and the clear exposition of important details. 17.g.13. Estimate implies a reasoned order of magnitude statement or calculation of the quantity concerned.g. especially where two or more steps are involved. or mass. using a rule. In general. 41 . 14. relative molecular mass. Sketch. 15. making such simplifying assumptions as may be necessary about points of principle and about the values of quantities not otherwise included in the question. freehand drawing is acceptable. In diagrams. Calculate is used when a numerical answer is required. implies that the shape and/or position of the curve need only be qualitatively correct. compasses. rectangle and diagonal • solve equations of the form x = yz for any one term when the other two are known. whole number indices • • draw charts and graphs from given data interpret charts and graphs • select suitable scales and axes for graphs • • make approximate evaluations of numerical expressions recognise and use the relationship between length. curve. diameter. 42 . parallelogram. circle. radius. fractions._subtract. set square) • understand the meaning of angle. square. percentages.6. multiply and divide use averages.6 Mathematical requirements Calculators may be used in all parts of the examination.. protractor. Candidates should be able to: • • • • add . decimals. ratios and reciprocals recognise and use standard notation use direct and inverse proportion • use positive. surface area and volume and their units on metric scales • use usual mathematical instruments (ruler. . 2 Boron 4 12 14 16 19 20 c N 0 F Ne Nrtrogen Carbon 'G· 5 7 Oxvgcn 8 No~ fluonnu 10 9 23 24 27 28 31 32 35.p..n 51 50 Bromme Selenli.Jrc~el Cobalt 28 27 Z•nc Copper 29 Gallrurll 31 30 101 103 106 108 112 115 Ru Rh Pd Ag Cd In Ruthenium 44 190 Rhodium 45 Palladium 46 Silver Cadmium 48 47 " Sulfur 16 Argcn Chlounc 18 17 73 75 79 80 84 Ge As Se Br Kr Gerrnar.t..5 40 Na Mg A/ Si p s C/ Ar Aluminium Srflcon Sod rum lvld(l<lf!SIUm 11 12 13 " 39 Ca K C~ICrum Potassrum 19 45 48 51 52 55 56 59 59 64 65 70 Sc Ti v Cr Mn Fe Co Ni Cu Zn Ga Scandium 20 Titamum 22 21 Vanadrurn 23 Chromium 24 85 88 89 91 93 96 Rb Sr y Zr Nb Mo Rubrdium 37 Yttrium Strontium 38 Zircomum 39 Nrobium 41 40 Iron Manganese 26 25 Tc Molybdenum Technetium 42 43 I.stat"'~ Radl>'1 -7 56 55 Fr fronc•um 87 ·ss-71 72 226 227 Ra Ac Rad•um 73 76 75 74 78 77 79 80 81 209 83 82 " c 86 85 actm•um 88 89 t Lanthanoid series t90-1 03 Actinoid series Key0 140 141 144 Ce Pr Nd Cerium PraseO<jy<'ltum 58 a = relat1vei.lss X= atomic symbol b =proton (atomic) number 90 Neodymium 60 59 232 Pm Prometh•um 150 152 157 159 163 165 167 169 173 175 Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Samanum 62 61 Europ•um 63 Tmb<um GadolllliUm 64 65 Dysp<osium 66 Hoi mourn Erb1um 68 67 Thuhum Luleuum Yumbium 71 70 69 238 Th Pa u Np Pu Am Cm Bl< Cf Es Fm Md No Lr Thorium PrO!OCII!liUffi Uran•um Neptumum PlutOnium Ameut•um Cunum Berkelium Cal•fornoum E•nsteu11um Ferm1um Mendelov1um ~lobelium Lawrencoum 91 92 93 94 95 96 97 98 99 The volume of one mole of any gas is 24 dm 3 at room temperature and pressure {r..J ' ' The Periodic Table of the Elements Group I II I I Ill I IV I v I VI I VII I 0 1 4 H He Heiiun1 Hydrogen 1 7 9 11 Li Be B Beryllrum Lrthrunl 3 .) ~ 101 102 ---'-- 103 .um 32 119 Arsemc 33 Krypton 36 35 122 128 127 131 Sb Te I Xe Antimony '.Bll 34 Sn tndrun1 49 Phosphorus 15 Xenon lod'na Teilunum 52 54 53 133 137 139 178 181 184 186 192 195 197 201 204 207 Cs Ba La Hf Ta w Re Os lr Pt Au Hg Tl Pb Bi Po At Rn c~esrum Barium Lanthanum Hafnium Tantalum Tun(!sten Rhenium Osm•um l<id•um Plahnum Gold Mercury Thallium Lead B•smulh Polon•um A.l tomic rn<. giving a dark blue solution green ppt. giving a colourless solution iron(II) (Fe 2 ') - Tests for gases gas test and test result ammonia (NH3 ) turns damp red litmus paper blue carbon dioxide (C0 2 ) turns limewater milky chlorine ( C 12 ) bleaches damp litmus paper hydrogen (Hz) 'pops' with a lighted splint oxygen (0 2 ) relights a glowing splint . warm carefully ammonia produced sulfate (SO/l [in solution] ~cidify. soluble in excess..l [in solution] add aqueous sodium hydroxide.. insoluble in excess zinc (Zn'•) white ppt. insoluble in excess iron(I!I) (Fe 3•) red-brown ppt. soluble in excess.. then add aqueous barium nitrate Tests for aqueous cations cation effect of aqueous sodium hydroxide effect of aqueous ammonia aluminium (A1 3') white ppt. soluble in excess giving a colourless solution white ppt. insoluble in excess no ppt. carbon dioxide produced chloride (CZ-) [in solution] acidify with dilute nitric acid.) ammonia produced on warming calcium (Ca2 ') white ppt.. soluble in excess. or very slight white ppt.... insoluble in excess light blue ppt. then add aqueous silver nitrate yellow ppt..CHEMISTRY 0620 IGC0to ZUlu NOTES FOR USE IN QUALITATIVE ANALYSIS Tests for anions anion test test result carbonate (CO 3 '-) add dilute acid effervescence. copper (Cu'•) light blue ppt.. insoluble in excess red-brown ppt.. then aluminium foil. giving a colourless solution white ppt. insoluble in excess ammonium (NH. nitrate (NO. then add aqueous silve~ nitrate white ppt. iodide (J) [in solution] acidify with dilute nitric acid.. white ppt. insoluble in excess green ppt. 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