Polymer: Chemistry Tingkatan 5 questions

Section A: objective questions

12 marks

Choose the best answer for each question.

What is a monomer?

The basic repeating unit that joins to form a polymer
A long-chain molecule made of repeating units
A by-product of polymerisation
A substance that coagulates latex

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A monomer is the basic unit that combines to form a polymer.

For the teacher: Remembering, low difficulty, standard 4.1.1

Textbook p. 144

Which pair is a natural polymer and its monomer?

Polystyrene and styrene
Starch and glucose
PVC and chloroethene
Nylon and glucose

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Starch is natural and made from glucose. The polymers named in A, C and D are synthetic, and glucose is not the monomer of nylon.

For the teacher: Remembering, low difficulty, standard 4.1.1

Textbook p. 144

Which polymer is a thermoset?

Polyethene
Nylon
Bakelite
Polyvinyl chloride

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Bakelite (and melamine) cannot be remoulded after heating. The others are thermoplastics.

For the teacher: Understanding, low difficulty, standard 4.1.1

Textbook p. 145

Which monomer can undergo addition polymerisation?

Ethane
Propane
Butane
Ethene

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Addition polymerisation needs a C=C double bond. Ethane, propane and butane are saturated.

For the teacher: Understanding, low difficulty, standard 4.1.2

Textbook p. 146

Which by-product is formed when nylon is made from 1,6-hexanediamine and decanedioyl dichloride?

Water
Carbon dioxide
Hydrogen chloride
Ammonia

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The acid chloride loses Cl and the amine loses H, so HCl forms.

For the teacher: Remembering, low difficulty, standard 4.1.2

Textbook p. 147

A polymer has the repeat unit -CH₂-CHCl-. What is the monomer?

Ethene
Chloroethane
Dichloroethene
Chloroethene

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Put the double bond back: CH₂=CHCl, chloroethene (vinyl chloride).

For the teacher: Applying, medium difficulty, standard 4.1.2

Textbook p. 146

Which action best reduces plastic waste in landfills?

Using biodegradable plastic additives
Burning plastic in the open
Dumping plastic into rivers
Using thicker plastic bags

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Additives let bacteria or light break plastic down, reducing waste.

For the teacher: Understanding, medium difficulty, standard 4.1.3

Textbook p. 150

What is the IUPAC name of the monomer of natural rubber?

Propene
2-methylbut-1,3-diene
Styrene
Ethene

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Isoprene is 2-methylbut-1,3-diene.

For the teacher: Remembering, low difficulty, standard 4.2.1

Textbook p. 151

Why does latex coagulate when ethanoic acid is added?

Hydroxide ions neutralise the rubber
The acid forms cross-links between chains
The acid dissolves the rubber particles
Hydrogen ions neutralise the negative charge on the protein membrane

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H⁺ neutralises the negative membrane, so particles no longer repel and clump together.

For the teacher: Understanding, medium difficulty, standard 4.2.2

Textbook p. 154

Why is ammonia solution added to latex stored for making gloves?

To make rubber elastic
To neutralise acid produced by bacteria
To form sulphur cross-links
To make latex solid

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OH⁻ neutralises the acid, so the membrane stays negative and the latex does not coagulate.

For the teacher: Understanding, low difficulty, standard 4.2.2

Textbook p. 155

What is formed between rubber chains during vulcanisation?

Sulphur cross-links
Hydrogen bonds
Ionic bonds
Double bonds

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Sulphur atoms bond at the C=C and link the chains.

For the teacher: Understanding, low difficulty, standard 4.2.3

Textbook p. 156

Which rubber is best for making a petrol hose, and why?

Natural rubber, because it is elastic
Unvulcanised rubber, because it is soft
Neoprene, because it resists oil and heat
Natural rubber, because it is biodegradable

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Neoprene resists heat, oxidation and solvents; natural rubber reacts with organic solvents.

For the teacher: Applying, medium difficulty, standard 4.3.2

Textbook p. 160

Section B: structured questions

34 marks

Answer all questions.

Polymers can be natural or synthetic.

[1 mark] (a)What is meant by a polymer?

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A long-chain molecule made from many repeating monomer units1

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[2 marks] (b)Name one natural polymer and its monomer.

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Starch / cellulose, glucose [1]1
(or protein, amino acid; natural rubber, isoprene)[1]1

Tick each point you got.

For the teacher: Understanding, low difficulty, standard 4.1.1

Textbook p. 144

The polymer PVC is made from chloroethene, CH₂=CHCl.

[1 mark] (a)Name the type of polymerisation.

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Addition polymerisation1

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[2 marks] (b)Draw the repeat unit of PVC.

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-CH₂-CHCl- with open bonds at both ends [1]1
Double bond no longer present (all C-C single) [1]1

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[2 marks] (c)Explain why PVC can be recycled.

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It is a thermoplastic [1]1
It softens on heating and can be remoulded [1]1

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For the teacher: Applying, medium difficulty, standard 4.1.2

Textbook p. 146

Nylon is made by condensation polymerisation of 1,6-hexanediamine and decanedioyl dichloride.

[2 marks] (a)State two differences between addition and condensation polymerisation.

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Addition: monomers have C=C; condensation: monomers have two functional groups [1]1
Addition: polymer only; condensation: a small molecule (water or HCl) is also formed [1]1

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[1 mark] (b)Name the small molecule formed when nylon is made.

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Hydrogen chloride (HCl)1

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For the teacher: Understanding, low difficulty, standard 4.1.2

Textbook p. 147

Plastic bags are the polymer product most thrown away in Malaysia.

[1 mark] (a)State one problem caused by disposing of plastic bags.

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Landfills fill up / marine life dies / microplastics enter the food chain1

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[2 marks] (b)Suggest two ways to reduce this problem.

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Recycle plastics [1]1
Use biodegradable or photodegradable plastics / reduce single-use plastics [1]1

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For the teacher: Understanding, low difficulty, standard 4.1.3

Textbook p. 149

Beaker A has latex with ethanoic acid, beaker B has latex with ammonia solution and beaker C has latex only.

[2 marks] (a)State what is observed in beaker A and beaker B.

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A: latex coagulates / solid forms [1]1
B: latex stays liquid [1]1

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[3 marks] (b)Explain the observation in beaker A.

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H⁺ ions from the acid neutralise the negative charge on the protein membrane [1]1
Rubber particles no longer repel and collide [1]1
Membranes break and the rubber polymers combine [1]1

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For the teacher: Understanding, medium difficulty, standard 4.2.2

Textbook p. 154

Diagram 1 shows the lengths of two rubber strips, M and N, of the same size. Each was stretched with a 50 g weight and then the weight was removed.

Strip M: 10 cm original, 18 cm with weight, 12 cm after. Strip N: 10 cm, 14 cm, 10 cm — Diagram 1

[1 mark] (a)Calculate the extension of strip M with the weight.

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18 - 10 = 8 cm1

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[3 marks] (b)Which strip is vulcanised rubber? Explain.

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Strip N [1]1
It stretches less and returns to its original length (10 cm) [1]1
Sulphur cross-links stop the chains sliding / pull it back [1]1

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[1 mark] (c)Which strip will snap first if the weight is increased?

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Strip M (unvulcanised)1

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For the teacher: Analysing, medium difficulty, standard 4.2.4

Textbook p. 157

Vulcanisation improves the properties of natural rubber.

[2 marks] (a)What is meant by vulcanisation?

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Process of making rubber more elastic and better quality [1]1
by forming sulphur cross-links between polymer chains [1]1

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[2 marks] (b)Why does vulcanised rubber resist oxidation better?

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Sulphur uses up the C=C double bonds [1]1
Fewer double bonds for oxygen to react with [1]1

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[1 mark] (c)State one advantage of vulcanisation by irradiation.

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Rubber free of sulphur / more environmentally friendly1

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For the teacher: Understanding, low difficulty, standard 4.2.3

Textbook p. 156

Surgical gloves can be made from natural rubber or from a synthetic rubber such as nitrile rubber.

[1 mark] (a)What is meant by synthetic rubber?

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A man-made elastomer (polymer) with rubber-like elasticity1

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[1 mark] (b)State one way synthetic rubber gloves differ from natural rubber gloves.

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Resist oil, solvents and heat better1

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[3 marks] (c)Justify the use of synthetic rubber, and state one drawback.

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Mass produced, not dependent on weather or disease [1]1
Resistant to heat, chemicals and oxidation [1]1
Drawback: takes very long to decompose [1]1

Tick each point you got.

For the teacher: Evaluating, high difficulty, standard 4.3.2

Textbook p. 161

Section A: objective questions

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Section B: structured questions

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20