Set 4PAPER 2 : STRUCTURE 1 SECTION A The diagram shows the chemical reaction of propanol. D E II Chemistry Perfect Score Module 2007 C3H8 C3H6 I III Propanol Propanoic acid IV Heat gently with ethanoic acid and concentrated sulphuric acid Y (a) (i) Name process reaction I …………………………………………………………………………………………………………. [ 1 mark ] (ii) Write the general formula of compound E. …………………………………………………………………………………................................. [ 1 mark ] Name process II. …………………………………………………………………………………................................. [ 1 mark ] What is the catalyst used in process II? ………………………………………………………………………………….................................. [ 1 mark ] (c) Describe a chemical test to distinguish compound D and E. …………………………………………………………………………………………………………. …………………………………………………………………………………………………………. …………………………………………………………………………………………………………. [ 3 marks ] Name a chemical used in process III to convert the propanol to propanoic acid. ………………………………………………………………………………………………………….. [ 1 mark ] (ii) What is the observation in process III? ………………………………………………………………………………………………………….. [ 1 mark ] (iii) Propanoic acid can reacts with magnesium. Write the chemical equation for the reaction. ………………………………………………………………………………….................................. [ 1 mark ] (b) (i) (ii) (d) (i) 1 Set 4 (e) (i) Chemistry Perfect Score Module 2007 A compound Y is formed in process IV. Name the compound Y ..........………………………………………………………………………………….................................. [ 1 mark ] What is the function of concentrated sulphuric acid in process IV? …………………………………………………………………………………………………………………. . [ 1 mark] (ii) 2 The diagram below shows the flow chart for the conversion of an organic compound to other compounds through process I, II ,III and combustion of compound L. Compound J C2H6O Compound K C2H4O2 III Acidified potassium dicromate(VI) solution I II Compound L C2H4 Complete combustion in air Gas X + H2O (a) (i) Name the homologous series to which L belong. …………………………………………………………………………………................................. [ 1 mark ] (ii) Name gas X. ………………………………………………………………………………….................................. [ 1 mark ] (iii) Write a balanced equation for the combustion of L in air ………………………………………………………………………………….................................. [ 2 marks ] (iv) 0.5 mole of L burn completely in the air. Calculate the volume of gas X released. 3 (1 mole of gas occupies 24 dm at room temperature and pressure) [ 2 marks ] (b) What is the observation on acidified potassium dichromate(VI) solution in reaction III? ………………………………………………………………………………………………………….. [ 1 mark ] 2 Set 4 (c) Chemistry Perfect Score Module 2007 Compound J reacts with compound K to form compound M. (i) Name compound M. ………………………………………………………………………………………………… [ 1 mark] Draw the structural formula of M. (ii) [ 1 mark ] (iii) State one special characteristic of compound M. ………………………………………………………………………………………………… [ 1 mark ] (d) Draw the set up of apparatus used in process II. [ 2 marks ] 3 The diagram below shows the chemical reaction of compound X. Compound X, C2H6O Acidified potassium manganate (VII) solution I Porous pot chips Gas Q II III Compound Z + water as Compound Y, C2H4O2 Reflux with compound X and concentrated sulphuric acid (a) Name compound X. ………………………………………………………………………………………………………….. [ 1 mark ] 3 Set 4 (b) (i) Name gas Q. Chemistry Perfect Score Module 2007 ………………………………………………………………………………………………… [ 1 mark ] (ii) What is the use of porous pot chips in process I? …................................................................................................................................. [ 1 mark] (c) (i) What is the observation on potassium manganate(VII) solution in process II? …………………………………………………………………………................................ [ 1 mark ] (ii) Draw the structural formula of Y. (d) [ 1 mark] The mixture of compound X, Y and concentrated sulphuric acid are heated under reflux in process III. (i) What is the use of concentrated sulphuric acid? ………………………………………………………………………………………………… [ 1 mark ] (ii) Write a balanced chemical equation for the reaction. ………………………………………………………………………………………………… [ 1 mark ] State one special characteristic of compound Z. ………………………………………………………………………………………………… [ 1 mark] (iv) X is replaced with butanol. Name the product formed. ………………………………………………………………………………………………… [ 1 mark ] (iii) 4 Set 4 4 Chemistry Perfect Score Module 2007 The diagram below shows the flow chart for the conversion of C2H4 and C3H7OH to other compounds. C2H5OH C2H5 COOH Process 1 Process 2 C3 H7OH C2H4 Polymerization Compound P C 3 H6 a) Name process I. ……………………………………………………………………………………………………………........... [ 1 mark] Draw the structural formulae of C2H4 and compound P in the equation below to represent the polymerisation of C2H4. . Polymerisation b) C2H4 c)(i) Name process 2. Compound P [ 2 marks] ………………………………………………………………………………………………………………........ [ 1 mark] (ii) Acidified potassium dichromate(VII) solution is used in process 2. State the observation on the colour change of acidified potassium dichromate(VI) solution. …………………………………………………………………………………………………………………….... [1 mark] d) Name the product formed from the dehydration of C3 H7OH ……………………………………………………………………………………………………………………… [1 mark] e) The products from process 1 and process 2 react to form a sweet smell compound. (i) Name the process for the formation of the compound. ………………………………………………………………………………………………………………… [1 mark] Draw the structural formula of the compound. (ii) [ 1 mark] (iii) Name the compound. …………………………………………………………………………………………………………………… [1 mark] 5 Set 4 f) Chemistry Perfect Score Module 2007 C3 H6 in the above diagram undergoes polymerisation. Name the polymer formed. ………………………………………………………………………………………………………………… [1 mark] The boiling point of C3H6 is higher than C2H4. Explain why. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………… [3 marks] g) 5 The diagram shows an industrial preparation of compound X from suphuric acid and ammonia. Contact Process Suphuric acid Reaction A Compound X Haber Process Ammonia (a) (i) Sulphur dioxide is produced at the stage I of contact process. Name the reactants for the formation of sulphur dioxide. ……………………..…………………………………………………………………........... [1 mark] (ii) Write a chemical equation for the reaction in (a) (i) ……………………..…………………………………………………………………........... [1 mark] (b) In Contact Process, oleum is produced. (i) Write the chemical equation for the formation of oleum. ……………………………………………………………………………….......................... [1 mark] How is sulphuric acid produced from oleum? ……………………………………………………………………………............................ [1 mark] (ii) . (c) Name the catalyst used in Contact Process. …………………………………………………………………………………………………………. [1 mark] 6 Set 4 (d) (i) Chemistry Perfect Score Module 2007 Write the chemical equation for the formation of ammonia in Haber Process .................................................................................................................................... [1 mark] (ii) State the temperature, pressure and catalyst used in the Haber Process. .................................................................................................................................... [1 mark] (e) In the above diagram, sulphuric acid reacts with aqueous ammonia to form compound X. (i) Name the reaction A. ...................…………………………………………………………………........................ [1 mark] (ii) Write the chemical equation for reaction A. ……………………………………………………………………………............................ [1 mark] (iii) What is the use of compound X in daily lives? ……………………………………………………………………….................................... [1 mark] 6. Bronze and pewter are two example of an alloy. Bronze is made up of copper as a major component and other elements. Bronze is harder than pure copper. (a) Name the main element added to copper to form bronze. ……………………………………………………………………………………………………………………. [1 mark] (b) What type of particles is present in pure copper? …………………………………………………………………………………………………………………… [1 mark] (c) Draw an arrangement of the particles in (i) Pure copper [1 mark] 7 Set 4 (ii) bronze Chemistry Perfect Score Module 2007 [1 mark] (d) Explain why is bronze is harder than pure copper? .............................................................................................................................................................. .............................................................................................................................................................. .............................................................................................................................................................. [3 marks] (e) (i) Name the major component of pewter. ............................................................................................................................................................... [1 mark] (ii) Beside hardness, state another purpose of alloying to produce pewter. .............................................................................................................................................................. [1 mark] 7 The table shows the examples and uses of four types of manufactured substances in industry. Type of manufactured substance Example Component P Reinforced concrete Cement, sand, small pebbles and steel. Copper and zinc Vinyl chloride Alloy Polymer Brass S (a) (i) Name the type of substance P. ………………………………………………………………………………………….......………………… [ 1 mark] (ii) Concrete in an important component in construction. Suggest how the strength of concrete is increased to be used as a pillars of building. ……………………………………………………………………………………………………………….. [ 1 mark] 8 Set 4 (b) The diagram shows the structure of S. Chemistry Perfect Score Module 2007 H C H H H H H C C C C Cl H Cl H Draw the structural formula for monomer S. [1 mark ] (c) The diagram below shows an industrial preparation of sulphuric acid by the Contact Process. Compound X, 1 atm Sulphur Sulphur dioxide + oxygen Sulphur trioxide 450 C – 500 C o o 500 C Concentrated H2SO4 o Sulphuric acid Compound Y (i) Name compound X and Y. Compound X :............................................................................................................. Compound Y : ............................................................................................................... [ 2 marks] (ii) Write the chemical equation for the reaction between sulphur and oxygen to produce sulphur dioxide. ....................................................................................................................................... [1 markah] 9 Set 4 8 Chemistry Perfect Score Module 2007 Diagram A shows the structural formula of a detergent and a soap. O // C O- Na+ Part P Part Q Detergent Part P Soap Part Q (a) Name part P and part Q of the detergent and soap molecules. ………………………………………………………………………………………………………….. [ 1 mark] (b) Differentiate the detergent and soap molecule the aspect of: Detergent Name of part Q Sources Effectiveness in hard water Soap [ 3 marks] (c) Some of detergent are not biodegradable .What is meant by not biodegradable? ………………………………………………………………………………………………………….. [ 1 mark] 9 Soap, detergent, food additive and modern medicine are important chemicals for consumer. a) The diagram shows the structural formula of a soap CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 + CH 2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 C-O Na || O Hydrophobic Hydrophilic i) State the property of hydrophobic and hydrophilic part of soap molecule. ........................................................................................................................................................ …………………………………………………………………………………………….......................... [2 mark] Detergent is more effective cleaning agent in hard water than soap. Explain why. ……………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………..… [2 marks] ii) 10 Set 4 b) Preservative and antioxidant are two types of food additive. i) State the function of antioxidant Chemistry Perfect Score Module 2007 ii) ……………………………………………………………………………………………………………….. [ 1 mark] Give one example of food preservative. ……………………………………………………………………………………………………………….. [ 1 mark] c) What is the type of medicine should be given to a patient who is stress and depressed . Give an example of the medicine. i) Type of medicine: ……………………………………………………………………………………………………………….. [1 mark] Example of medicine: ……………………………………………………………………………………………………………….. [1 mark] ii) 11 Set 4 ESSAY SECTION B 10 (a) Chemistry Perfect Score Module 2007 Soap and detergent are two cleansing agents that we used in our daily life. (i) (ii) Explain the cleansing action of soap on greasy stains. [6 marks] Explain why detergent is more effective than soap as a cleansing agent in hard water. [5 marks] (b) Aspirin is an example of analgesic that should never be given to children. (i) (ii) (iii) What is meant by `analgesic`? State two examples of analgesics besides aspirin. [1 mark] [2 marks] Discuss four uses of aspirin and two side effects on health of using aspirin. [6 marks] 11 (a) Alcohol Q contains 52.2% carbon, 13.0% hydrogen and 34.8% oxygen by mass. (i) Determine the empirical formula and molecular formula of alcohol Q if the -1 molar mass of alcohol Q is 46 gmol . Relative atomic mass of H=1, C=12 dan O=16 [6 marks] (ii) Draw the structural formula of alcohol Q. [1 mark] (b) Describe how you could produce alcohol Q from glucose, C6H12O6. [8 marks] Describe how you could produce an acid from alcohol Q in the laboratory. In your answer, include the chemical equation for the reaction involved. [5 marks] (c) 12 Set 4 ESSAY SECTION C 12 (a) Chemistry Perfect Score Module 2007 Sulphuric acid is an example of manufactured substance in industry that has many uses in our daily life. (i) (ii) (b) . Steel and stainless steel are examples of alloys and their major metal is iron. Describe how you could compare the rate of rusting between iron, steel and stainless steel. Your answer should include tabulation of data and conclusion. [10 marks] State three uses of sulphuric acid. Describe the process of producing sulphuric acid in industry. [3 marks] [7 marks] 13 Diagram below shows the convertion of organic compound X to Z and organic compound X to Y. Z a) Oxidation X (C3H7OH) Dehydration Gas Y Compound X can form a few isomers. (i) (ii) What is meant by `isomer`? Draw the structural formulae and name all the isomers of compound X. [5 marks] b) Gas Y can be obtained from compound X through dehydration reaction. Describe how you could produce gas Y from compound X. In your answer, include (i) (ii) (iii) a labelled diagram to show the set-up of apparatus name of gas Y a test to confirm the presence of gas Y. [10 marks] c) Compound X can be oxidized to compound Z. Compound X can react with Z to produce an ester. (i) Name compound Z. (ii) Write the chemical equation for the oxidation of compound X. (iii) Name the ester that is formed from reaction betwen X and Z. State two physical properties of the ester. [5 marks] 13 Set 4 Chemistry Perfect Score Module 2007 Paper 3 14 The diagram below shows the apparatus set-up for an experiment to compare the elasticity properties of vulcanised rubber and unvulcanised rubber. Clip Rubber strip Ruler Weight An experiment is carried out using weights of 10g, 20g and 30g to get the increase in length of the vulcanised rubber and the unvulcanised rubber. The table below shows the results obtained from the experiment. Types of rubber Weights (g) Initial length, l1 (cm) Length after stretching, I2 (cm) Increase in length, I2 –I1 (cm) Increase in length after weight is removed. (cm) 8.5 9 9.5 10 12 14 10 8 10 Vulcanised rubber 20 8 12 30 8 11 Unvulcanised rubber 10 8 12 20 8 16 30 8 20 a) b) Complete the table above based on the above experiment. [3 marks] State one hypothesis for this experiment. ………………………………………………………………………………………………… ……………………………………………………………………………………………….... ………………………………………………………………………………………………… [3 marks] 14 Set 4 c) Name of variables (i) Manipulated variable: …………………………………….. …………………………………….. (ii) Responding variable: …………………………………… Chemistry Perfect Score Module 2007 Based on the information above, complete the following table. Action to be taken (i) The way to manipulate variable: ……………………………………….. ………………………………………... (ii) What to observe in the responding variable: ……………………………………….. ………………………………………..……… …………………………………… (iii) Controlled variable: …………………………………….. …………………………………….. (iii) The way to maintain the controlled variable: ……………………………………… ……………………………………… [6 marks] d) i) Based on the experiment above, which rubber strip is more elastic? ………………………………………………………………………………………………………….. [3 marks] Explain your answer in (d) (i). ii) ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. [3 marks] Give the definition of vulcanised rubber? ……………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………. [3 marks] 15 Copper wire in an electric cable can be bent with our bare hands. One cent shilling made from the alloy of copper with tin and zinc cannot be bent easily. e) Referring to the above situation, plan an experiment in the laboratory to investigate the effect of alloying towards the hardness of pure metal. Your planning should include the following: (i) Statement of the problem (ii) Hypothesis (iii) Variables (iv) List of substances and apparatus (v) Procedures (vi) Tabulation of data [17 marks] 15 Set 4 Sample Answer 1 Chemistry Perfect Score Module 2007 (a) (i) Dehydration (ii) CnH2n+2 (b) (i) Hydrogenation / addition with hydrogen (ii) Nicel/Platinum (c) Add bromine water and shake E decolourises the brown colour of bromine water. D does not change the brown colour of bromine water. (d) (i) Acidified potassium manganate(VII)/ Acidified potassium dichromate(VI) (ii) Purple to colourless / orange to green. (iii) C2H5COOH + Mg (C2H5COO) 2Mg + H2 (e) (i) Propyl ethanoate (ii) Catalyst 2 (a) (i) (ii) (iii) (iv) Alkene Carbon dioxide C2H4 + 3O2 → 2CO2 + 2H2O 1 mol C2H4→2 mol CO2 // 0.5 mol C2H4 → 1 mol CO2 Volume of gas X / CO2 = 1 x 24 dm // 24 dm (b) ( c) Orange to green (i) ethyl ethanoate (ii) O // CH3-C – O – C2 H5 (iii) sweet smell (d) Functional diagram Label 3 3 1 1 1 1 1 1 1 1 1 1 1+1 1 1 1 1 1 1 1 1 12 3 (a) (b) ethanol (i) ethane (ii) Functional diagram Label 1 1 1 1 (c) (i) (ii) Purple to colorless 1 H O 1 H - C - C-O-H H catalyst CH3CH2OH + CH3COOH CH3COOCH2CH3 + H2O sweet smell butyl ethanoate (d) (i) (ii) (iii) (iv) 1 1 1 1 10 16 Set 4 4 a) b) Hydration Chemistry Perfect Score Module 2007 H C H H C H n 1 1 1 1 1 n c) d) e) (i) Oxidation (ii) Orange of to green Propane (i) Esterification (ii) H H C H (iii) f) g) Ethyl propanoate H C H O C O H C H H C H 1 1 1 1 1 1 1 1 1 1 1 1 1 1 H Polypropane The size of propane molecule is larger than ethane molecule The intermolecular forces between propane molecules stronger than ethane More energy is needed to overcome the forces between propane. 5 a(i) (ii) b (i) (ii) c d (i) ii) e (i) (ii) (iii) Sulphur and oxygen gas S + O2 SO2 SO3 + H2SO4 H2S2O7 Dissolve SO3 in concentrated sulphuric acid Vanadium(v) oxide 3H2 + N2 2NH3 o [450 C], [200 atm], Iron Neutralization H2SO4 +2 NH4OH Fertilizer (NH4)2SO4 +2H2O 1 1 6 (a) Tin (b) Atom (c) (i) (ii) Copper atom Tin atom Copper atom (d) 1. Atoms of pure copper metal are the same size, they arranged orderly in layered pattern. 2. Layers of atoms are easily slide over each other when external force is applied on them. 3. Foreign atoms in alloy disrupt the orderly arrangement of metal atoms 17 Set 4 (e) (i) Tin (ii) Improve appearance / prevent corrosion. Chemistry Perfect Score Module 2007 4. Layers of metal atoms are prevented from sliding each other when external force is applied. 7 a) (i) Composite material (ii) Add steel b) H H C=C H Cl f) (i) X : vanadium (v) oxide Y : Oleum (ii) S + O2 SO2 1 1 1 1 1 1 1 6 8 (a) (b) hydrocarbon/ hydrophobic 1 Name of part Q Sources Effectiveness in hard water Soap Carboxylate Oil Not effective Detergent Sulphonate petroleum Effective 1+1+1 (c) Cannot decomposed by microorganism 1 1 9 a) i) Hydrophobic dissolve in organic solvent Hydrophilic dissolve in water ii) Soap forms scum with the presence of magnesium ion and calcium ion. Detergent does not form scum in hard water. iii) Not biodegradable. b) (i) Prevent food from being oxidized by oxygen in the oxygen in the air. (ii) sodium benzoate c) (i) Antidepressant (ii) Tranquilizer / Barbiturate 1 1 1 1 1 1 1 1 1 9 18 Set 4 SECTION B 10 (a) (i) 1. 2. 3. 4. 5. 6. Chemistry Perfect Score Module 2007 Soap anion consists of hydrophilic and hydrophobic. Hydrophilic dissolves in water. Hydrophobic dissolves in oils/grease. Soap reduces surface tension of water. Hydrophobic emulsify oil or grease. During rinsing, soap will remove the grease 2+ 1 1 1 1 1 1….6 2+ (ii) 1. Hard water contains calcium ions/Ca 2. 3. 4. 5. and magnesium ions/ Mg 1 2+ Soap anions react with calcium ions/Ca or magnesium ions/ 2+ Mg to form scum 1 Scum is insoluble in water 1 Waste soap 1 Detergent does not form scum 1....5 (b) (i) Medicine used to relieve pain without causing numbness or affecting consciousness Paracetamol Codeine 1. 2. 3. 4. 1…1 1 1…2 (ii) (iii) Relieves pain caused by headache, toothache Reduces fever Treat arthritis /reduce inflammation of the joints Reduces blood clotting / prevents stroke / prevents heart attacks a. Reduces inflammation caused by infection or injury (any four) 1+1+1+1....4 1. Causes internal bleeding of the stomach / Ulceration 2. Causes brain / liver damage if given to children 3. Overdose causes death (any two) 1+1....2 20 11 (a) Element 1. Number of moles of atoms 2. Ratio C 52.2 12 =4.35 2 H 13.0 1 =13.0 6 O 34.8 16 =2.175 1 1 1 1 1 1 1 3. Empirical formula of Q is C2H6O Relative molecular mass of (C2H6O) n = 46 4. 2n(12) + 6n(1) + n(16) = 46 46n = 46 5. n=1 6. Molecular formula of Q is C2H6O / C2H5OH 7. Structural formula is H H H - C - C -OH H H 1....7 19 Set 4 (b) 1. Add glucose into a conical flask. 2. Add water. 3. Add yeast. 4. Close the conical flask 5. Leave the flask for 1 to 3 days. 6. Filter the content 7. Distille the filtrate 0 8. Collect the fraction that boils at 78 -80 C 1. 2. 3. 4. 5. Add alcohol Q in a test tube. Add acidified potassium manganate (VII) solution Heat the solution. The purple colour of the solution turns colourless [Chemical equation] Chemistry Perfect Score Module 2007 1 1 1 1 1 1 1 1....8 1 1 1 1 1....5 20 (c) SECTION C 12 ( a)(i) 1. Manufacture fertilisers 2. Manufacture detergents 3. As an electrolyte in car batteries 4. Manufacture paint pigments 5. Synthetic fibres 6. Plastics 7. Clean metals 8. Pesticides [any 3 above] 1+1+1....3 (ii) 1. Sulphur is burnt in the air // Zinc sulphide is burnt to produce sulphur dioxide // Equation S + O2 3O2 SO2 // 2ZnO + 2SO2 1 2ZnS + 2. Sulphur dioxide react with oxygen to produce sulphur trioxide // Equation 2SO2 + O2 o 2SO3 1 1 1 1 3. Catalyst: vanadium(V) oxide 4. Temperature: (400 – 500 C) 5. Pressure: 1 atm 6. Sulphur trioxide reacts with concentrated sulphuric acid to produce oleum // Equation: SO3 H2S2O7 + b) + H2SO4 H2S2O7 2H2SO4 1 7. Oleum is diluted with water to produce sulphuric acid // Equation H2O 1..7 1. Material: iron nail, steel nail, stainless steel nail, jelly solution, potassium hexacyanoferrate(III) solution 1 2. Apparatus: Test tubes, test tube rack 3. Put iron nail in test tube A, steel nail in test tube B and stainless steel in test tube C 4. Add jelly solution and a few drops of potassium hexacyanoferrate(III) solution into the test tubes 5. Pour the jelly solution until the nails are fully immersed 6. Leave the test tubes for 2-3 days 1 1 1 1 1 20 Set 4 7. Observation Test tube A (Iron nail) B (Steel nail) C (Stainless steel nail) Intensity of blue colour High Low Nil Chemistry Perfect Score Module 2007 1 8. Potassium hexacynoferrate(III) solution to detect iron(III) ions 9. The higher the intensity of the blue colour, the higher the rate of rusting 10. Rate of rusting of iron is the highest follow by steel and stainless steel does not rust 1 1 1..10 20 13 (a) Isomers are molecules/compounds which have same molecular formulae but different structural formulae. 1 H H H │ │ │ H─C─ C ─ C─ OH │ │ │ H H H Propan-1-ol H OH H │ │ │ H – C─ C ─ C ─ H │ │ │ H H H Propan-2-ol 1+1 1+1..5 (b) 1. Functional set-up of apparatus 2. Label 3. Place the glass wool in a boiling tube. Add propanol/C3H7OH to the glass wool. 4. Place the porcelain chips in the tube. 5. Heat the porcelain strongly. 6. Heat the glass wool. 7. Collect gas Y using test tube. 8. Gas Y is propene. 9. Add bromine water (acidified potassium manganate(VII) solution) to the test tube. 10.Brown colour of bromine decolourised (purple colour of potassium manganate(VII) decolourised) X –propanoic acid C3H7OH + 2[O] → C2H5COOH + H2O Ester –propyl propanoate Sweet pleasant smell (fruity smell) Less dense than water Insoluble in water Colourless liquid Volatile (any two) 1 1 1 1 1 1 1 1 1 1..10 1 1 (c) (i) (ii) (iii) 1 1+1..5 20 21 Set 4 Paper 3 14 (a) To measure using numbers Chemistry Perfect Score Module 2007 Score Explanation 3 Able to record all the six readings correctly. Suggested answer Vulcanised rubber: 2, 4, 6 Unvulcanised rubber: 4, 8, 12 1(b) To make hypothesis Score Explanation 3 Able to relate between the manipulated variable and the responding variable. Suggested answer Vulcanised rubber is more elastic than the unvulcanised rubber// Unvulcanised rubber is less elastic than the vulcanised rubber 1(c) To control variable Score Explanation 6 Suggested answer Variable (i) Manupilated variable Vulcanized and unvulcanized rubber// Mass of weight (ii) Responding variable Increase in length of rubber strip//elasticity (iii) Fixed variable Initial length of rubber strip Action to be taken (i) The way to manupilate variable Repeat by replacing vulcanized rubber with unvulcanized rubber//Use weights with different masses (ii) What to observe in the responding variable To measure length of rubber strip (iii) The way to maintain the controlled variable Use the same length of vulcanized and unvulcanized rubber strips 1(d) To make inference Score Explanation 3 Able to make the correct inference Suggested answer: (i) Vulcanized rubber (ii) Presence of the sulphur cross links between the chain of rubber polymers in vulcanized rubber makes the small increase in length and can return to its original length after stretching. 1(e) Operational definition: Score Explanation 3 Able to make an operational definition correctly: Suggested answer: Rubber that can stretch a bit and returns to its original length when not stretched. 22 Set 4 15 (i) Chemistry Perfect Score Module 2007 Rubric [Able to give the correct problem statement.] Suggested answer: How does alloying affects the hardness of metal?//What is the effect of alloying towards the hardness of metal? [Able to state all the variables correctly] Suggested answer: Manipulated variable: metal and its alloy//copper and brass/bronze// iron and steel Responding variable: size/diameter of dent Fixed variable : Mass of weight//height of weight//type of metal of ball bearing// size of ball bearing [Able to list completely the substances and apparatus] Example: Metal (named), its alloy(named) Steel ball bearing, weight, ruler, rope/thread, retort stand [Able to state the procedures correctly] Example: 1. Put a ball bearing on a metal block/its alloy. 2. Hang a weight until (50-100 cm) above the metal block/its alloy 3. Let the weight fall. 4. Measure and record the diameter of the dent formed. 5. Repeat the activity a few more times 6. Repeat steps 1 – 5 by replacing the metal with its alloy// alloy wits metal [Able to show the correct tabulation of data] Table with the following elements: 1. 4 colums and 3 rows 2. Titled metal (named), its alloy (named), diameter (with unit), Average (with unit) Example Diameter (cm) Average(cm) 1 2 Metal (named) Alloy(named) Scor e 3 (ii) 3 (iii) 3 (iv) 3 (v) 3 23