ps f4 set 5

Set 5 Marking Scheme :Manufactured Substances in Industry 2010

Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 5 38

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) (ii)

NH3 + CO2 → CO(NH2)2 + H2O RMM urea = 60 % N = 2(14) x 100 60 = 46.6%

1

1 1

(g) 1.Blue precipitate soluble in excess ammonia solution 2.Forming dark blue solution

2

2(a)(i) (ii)

Contact process Haber Process

1 1

(b)(i) (ii)

2SO2 + O2 → 2 SO3 Vanadium(V) oxide

1 1

(c)(i) (ii)

N2 + 3H2 → 2NH3 Temperature, 450oC , Pressure 200 atm

1 1

(d)(i) (ii) (iii)

Ammonium sulphate (NH4)2SO4 RMM ammonium sulphate = 132 % N = 2(14) x 100 = 21.2 % 132

1

2

(e) Manufacture of detergents/ production of fertilizer/ manufacture of artificial fibres/ manufacture of paint / leather tanning/ as electrolyte in car batteries

1

3(a)

Large molecules made up of many identical repeating sub-units called monomers which are joined together by covalent bonds.

1

(b) Monomer Polymer Amino acid Protein

Glucose Starch Ethene Polyethene

Isoprene Natural rubber

4

(c)

H H | | ── C ── C ── | | H H n

(d)(i) (ii)

PVC does not rust, iron will rust

(e) Natural polymer – protein, starch, natural rubber Synthetic polymer – polyethene, polychloroethene

Cl



PAPER 2: ESSAY No. Answer Marks 4(a)(i) (ii) (iii)

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 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 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

3

3

(b)(i) (ii) (iii)

1. aluminium is a pure metal 2. it is soft and not strong / cannot withstand compression 1. duralumin 2. an alloy of aluminium that stronger and harder than aluminum. 3. can withstand compression 4. yet is light as aluminium 1. tin and copper 2.stronger than tin 3. able to withstand corrosion 4. shinier surface than tin

2

4

4

20 5(a)(i) (ii)

Large/long/giant/big chain smaller molecules/monomers made from joining of smaller monomers.

Synthetic polymers

Monomers Uses

Polythene Ethene Plastic bags/ containers/ electrical wiring

Polypropene Propene Piping / bottle crates/ carpets / car batteries/ ropes

Polyvinyl Chloride

Chloroethene/vinyl chloride Artificial leather/water pipes

Perspex Methylmethacrylate/methyl 2-methyl propenoate

Safety glass/reflectors/lens

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

1

6

(b)(i) Formed by combining two or more different substances/ materials 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

2



Photochromic glass Optical lenses/car windshields/windows in buildings/ information display panels/ lens in cameras/optical switches

Names of 2 composites material. Respective use.

4

(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. 8. The air pollution index reading will increase // air quality become worse // causing the air pollution. ( choose any 7 above )

7

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 Different type of material

The way to manipulate variable Repeat the experiment by using brass block to replace copper block.

Responding variable Diameter of the dent

What to observe in the responding variable Observe the different diameter made by the ball bearing on both copper and brass.

Fixed variable Mass and height of the weight, size of the steel ball bearing

Way to maintain fixed variable: Use the same mass and height of the weight and size of the ball bearing in each experiment

(d) Bronze is harder than copper

(e)

Pure metal: iron, copper, aluminium Alloy : bronze, duralumin



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) (ii) (iii)

Concrete and reinforce concrete Hardness of the material 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) (ii)

To make sun glasses / window panes / camera lenses 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

3

[ Able to state the problem statement clearly and accurately] Suggested answer Does iron rust faster than steel?

2

[Able to state the problem statement slightly inaccurate] Suggested answer To study the rusting of iron and steel.

1 [Able to provide an idea of a problem statement] Suggested answer

The rusting of iron and steel 8 (ii) KK051202 – Stating all variables Score Rubric

3

[Able to state all the corresponding variables accurately] Suggested answer Manipulated variable : Iron and steel 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].



8 (iii) KK051202 – Statement of hypothesis Score Rubric

3

[Able to state the relationship between manipulated variable and responding variable correctly] Suggested answer: Iron rusts faster than steel.

2

[Able to state the relationship between manipulated variable and responding variable but in reverse direction] Suggested answer: Steel rusts faster than iron

1 [Able to state an idea of the hypothesis] Suggested answer: Iron and steel rust.

8. (iv) KK051205 – List of materials and apparatus Score Rubric

3

[Able to list all materials and apparatus correctly] Suggested answer Materials Iron nail, steel nail, jelly solution, potassium hexacyanoferrate(III) solution, Sandpaper, Water. Apparatus :Test tubes

2

[Able to list the basic materials and apparatus required] Suggested answer Iron nail, steel nail, potassium hexacyanoferrate(III) solution Apparatus : Test tubes

1 [Able to provide an idea of materials and apparatus used] Suggested answer Iron nail, steel nail, jelly solution

8. (v) KK051204 – Experimental procedure

Score Rubric

3

[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. 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.

2 [Able to provide 3 steps correctly to carry out the experiment]

Steps 2, 3 and 4

1 [Able to provide minimum of 2 steps correctly to carry out the experiment] Steps 2 and 3



8. (vi) KK 0501-05 – Tabulation of data Score Rubric

3

[Able to construct a table correctly containing the following elements] - Columns and rows - Observation for each test tube

Suggested answer

Test tube No. Intensity of blue colour

1

2

2

[Able to construct a tabulation of data containing the following elements] - Rows and columns present - Observation Suggested answer

Test tubes Observation

1

[An idea of a tabulation of data ] - Minimum of 2 rows and columns

ps f4 set 5

Business