Marking scheme-chemistry-perfect-score-module-form-4-set-5


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Marking scheme-chemistry-perfect-score-module-form-4-set-5

  1. 1. Set 5 Marking Scheme :Manufactured Substances in Industry 2010 PAPER 2 : STRUCTURE NO. Answer Marks 1(a) Haber Process 1 (b) N2 + 3H2 → 2NH3 1 (c) Iron 1 (d) Temperature, 450oC , Pressure 200 atm 1 (e) Ammonium sulphate 1 (f)(i) NH3 + CO2 → CO(NH2)2 + H2O 1 (ii) RMM urea = 60 % N = 2(14) x 100 1 60 1 = 46.6% (g) 1.Blue precipitate soluble in excess ammonia solution 2 2.Forming dark blue solution 2(a)(i) Contact process 1 (ii) Haber Process 1 (b)(i) 2SO2 + O2 → 2 SO3 1 (ii) Vanadium(V) oxide 1 (c)(i) N2 + 3H2 → 2NH3 1 (ii) Temperature, 450oC , Pressure 200 atm 1 (d)(i) Ammonium sulphate 1 (ii) (NH4 )2SO4 (iii) RMM ammonium sulphate = 132 % N = 2(14) x 100 = 21.2 % 2 132 (e) Manufacture of detergents/ production of fertilizer/ manufacture of artificial fibres/ 1 manufacture of paint / leather tanning/ as electrolyte in car batteries 3(a) Large molecules made up of many identical repeating sub-units called monomers which 1 are joined together by covalent bonds. (b) Monomer Polymer 4 Amino acid Protein Glucose Starch Ethene Polyethene Isoprene Natural rubber (c) H H | | ── C ── C ── | | H H n (d)(i) PVC does not rust, iron will rust (ii) Cl (e) Natural polymer – protein, starch, natural rubber Synthetic polymer – polyethene, polychloroethene Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 5 38
  2. 2. Set 5 Marking Scheme :Manufactured Substances in Industry 2010 PAPER 2: ESSAY No. Answer Marks 4(a)(i) 1. pure metal atom have similar size and shape 2. arranged closely and form layers of atoms 3.when force is applied, layers of atoms slide on each other easily 3 (ii) 1. the atoms of the foreign metal added to pure metal have different size 2. these atoms distrupts the arrangement of the pure metal atoms 3. preventing the layers of metal from sliding on one another easily 3 (iii) 1. increase the strength and hardness of metal 2. prevent corrosion of metal 3. improve the appearance of metal and make it more attractive. 3 (b)(i) 1. aluminium is a pure metal 2. it is soft and not strong / cannot withstand compression 2 (ii) 1. duralumin 2. an alloy of aluminium that stronger and harder than aluminum. 4 3. can withstand compression 4. yet is light as aluminium (iii) 1. tin and copper 2.stronger than tin 4 3. able to withstand corrosion 4. shinier surface than tin 20 5(a)(i) Large/long/giant/big chain smaller molecules/monomers made from joining of smaller 1 monomers. Synthetic Monomers Uses (ii) polymers Polythene Ethene Plastic bags/ containers/ electrical wiring Polypropene Propene Piping / bottle crates/ carpets / car batteries/ ropes Polyvinyl Chloroethene/vinyl chloride Artificial leather/water pipes Chloride Perspex Methylmethacrylate/methyl Safety glass/reflectors/lens 2-methyl propenoate 6 Terylene Hexane-1,6-diol Clothing/sails/ropes Nylon 1,6-diamine hexane Rope/clothing/carpets Name of 2 synthetic polymers 2 marks their are respective monomers 2 marks 2 uses (b)(i) Formed by combining two or more different substances/ materials 2 That is better/stronger/superior /durable than the original component. Composites material Uses Reinforced Concrete Buildings / bridges/ oil platforms Superconductors Magnetic energy-storage systems/ generators/ transformers/ computer parts Fibre optic Telephone lines/ mobile phones/video cameras/ LAN Fibre glass Household products: water storage tanks/ badminton rackets/small boats/skis/helmets Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 5 39
  3. 3. Set 5 Marking Scheme :Manufactured Substances in Industry 2010 Photochromic glass Optical lenses/car windshields/windows in buildings/ information display panels/ lens in 4 cameras/optical switches Names of 2 composites material. Respective use. (c) 1. Sulphur dioxide gas / toxic waste dissolves in rain / water to form acid rain /acid dissolved in water. 2. Acid rain lowers the pH value of water / soil / air/ increases acidity. 3. Causing the death of plants. 4. Causing the death of aquatic creatures/fish 5. Causing damage to buildings / vehicles. 6. Decay of aquatic creatures by bacteria causing 7. The oxygen content in water to become less// (BOD) increases. 7 8. The air pollution index reading will increase // air quality become worse // causing the air pollution. ( choose any 7 above ) 20 PAPER 3: STRUCTURE No. Answer 6(a) Copper : 0.53 cm Brass : 0.27 (b) Operation definition: if the dent is smaller, the material is harder (c) Manipulated variable The way to manipulate variable Different type of material Repeat the experiment by using brass block to replace copper block. Responding variable What to observe in the responding variable Diameter of the dent Observe the different diameter made by the ball bearing on both copper and brass. Fixed variable Way to maintain fixed variable: Mass and height of the weight, size of the Use the same mass and height of the weight steel ball bearing and size of the ball bearing in each experiment (d) Bronze is harder than copper Pure metal: iron, copper, aluminium (e) Alloy : bronze, duralumin Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 5 40
  4. 4. Set 5 Marking Scheme :Manufactured Substances in Industry 2010 No. Answer 7(a) Concrete is a composite material consisting of small stones and sand bound together by cement. (b) Steel , steel is strong and high tensile stength (c) Make pillars of high rise buildings Make pillars of bridges Make pillars of oil rig platform (d) Is reinforced concrete stronger than concrete ? (e)(i) Concrete and reinforce concrete (ii) Hardness of the material (iii) Height dropped of the weight, mass of the weight, size of the reinforced concrete (f) The strength of the composite material is the ability of the material to withstand an impact (force). The stronger the material, the heavier the weight required to break the material. (g)(i) To make sun glasses / window panes / camera lenses (ii) Silver nitrate solution is added to sodium chloride solution in a beaker and stirred. The mixture is filtered and the precipitate rinsed with distilled water. The precipitate is dried in an oven PAPER 3 : ESSAY 8. (i) KK051201 - Problem statement No. Rubric [ Able to state the problem statement clearly and accurately] Suggested answer 3 Does iron rust faster than steel? [Able to state the problem statement slightly inaccurate] Suggested answer 2 To study the rusting of iron and steel. [Able to provide an idea of a problem statement] 1 Suggested answer The rusting of iron and steel 8 (ii) KK051202 – Stating all variables Score Rubric [Able to state all the corresponding variables accurately] Suggested answer Manipulated variable : Iron and steel 3 Responding variable : Intensity of amount of blue colour Fixed variables : Siza of nails, concentration of solutions used, duration for rusting 2 [Able to state two corresponding variables accurately]. 1 [Able to state any one corresponding variable correctly]. Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 5 41
  5. 5. Set 5 Marking Scheme :Manufactured Substances in Industry 2010 8 (iii) KK051202 – Statement of hypothesis Score Rubric [Able to state the relationship between manipulated variable and responding variable correctly] Suggested answer: 3 Iron rusts faster than steel. [Able to state the relationship between manipulated variable and responding variable but in reverse direction] 2 Suggested answer: Steel rusts faster than iron [Able to state an idea of the hypothesis] 1 Suggested answer: Iron and steel rust. 8. (iv) KK051205 – List of materials and apparatus Score Rubric [Able to list all materials and apparatus correctly] Suggested answer Materials 3 Iron nail, steel nail, jelly solution, potassium hexacyanoferrate(III) solution, Sandpaper, Water. Apparatus :Test tubes [Able to list the basic materials and apparatus required] Suggested answer 2 Iron nail, steel nail, potassium hexacyanoferrate(III) solution Apparatus : Test tubes [Able to provide an idea of materials and apparatus used] 1 Suggested answer Iron nail, steel nail, jelly solution 8. (v) KK051204 – Experimental procedure Score Rubric [Able to state all experimental steps correctly] Suggested answer 1. Rub nails with sandpaper until clean of rust. 2. Put iron nail in test tube 1 and steel nail in test tube 2. 3 3. Add jelly solution containing potassium hexacyanoferrate(III) into the test tubes until the nails are completely immersed in it. 4. Leave the nails for three days. 5. After three days, observe the intensity of the blue colour. [Able to provide 3 steps correctly to carry out the experiment] 2 Steps 2, 3 and 4 [Able to provide minimum of 2 steps correctly to carry out the experiment] 1 Steps 2 and 3 Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 5 42
  6. 6. Set 5 Marking Scheme :Manufactured Substances in Industry 2010 8. (vi) KK 0501-05 – Tabulation of data Score Rubric [Able to construct a table correctly containing the following elements] - Columns and rows - Observation for each test tube Suggested answer 3 Test tube No. Intensity of blue colour 1 2 [Able to construct a tabulation of data containing the following elements] - Rows and columns present - Observation Suggested answer 2 Test tubes Observation [An idea of a tabulation of data ] 1 - Minimum of 2 rows and columns Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 5 43