AQA GCSE Chemistry Chemistry Paper 2 (Foundation), June 2024: Question 6

9 marks · Standard Demand difficulty · Short Answer

Identify properties, reactions, and polymer structures related to alkenes, calculate a density ratio, and evaluate polymer suitability and sustainability.

Practise this question

Question

Question text

06 This question is about addition reactions.

Figure 7 shows the displayed structural formula of ethene.

Figure 7

06.1 Complete the sentence.

[1 mark]

When bromine water is added to ethene, the bromine water changes from orange to

Chlorine reacts with ethene.

06.2 What is used to identify chlorine?

[1 mark]

Tick ( ) one box.

A lighted splint

Damp litmus paper

Limewater

06.3 Which of the following shows the displayed structural formula of the compound

produced when chlorine reacts with ethene?

Use Figure 7.

[1 mark]

Tick ( ) one box.

06.4 Chloroethene can be used to produce a polymer called poly(chloroethene).

The displayed structural formula of chloroethene is

Which represents the structure of poly(chloroethene)?

[1 mark]

Tick ( ) one box.

Ethene can be used to produce another polymer called poly(ethene).

Table 3 shows information about poly(chloroethene) and poly(ethene).

Table 3

Poly(chloroethene) Poly(ethene)

Density in g/cm3 1.5 0.9

Temperature at which polymer

*26* 260 120

completely melts in °C

06.5 Determine the simplest whole number ratio of the

density of poly(chloroethene) : density of poly(ethene).

[3 marks]

Simplest whole number ratio = :

06.6 Poly(ethene) and poly(chloroethene) can both be used to make pipes.

Suggest why neither polymer is suitable for pipes carrying steam at a temperature of

300 °C.

Use Table 3.

[1 mark]

06.7 Poly(ethene) and paper can both be used to make shopping bags.

Poly(ethene) is produced from crude oil. Paper is produced from trees.

Suggest one reason why paper is more sustainable than poly(ethene) for making

shopping bags.

[1 mark]

Mark scheme

Show the mark scheme

Question 6

AO /

Question Answers Extra information Mark

Spec. Ref.

06.1 colourless ignore clear 1 AO1

4.7.1.4

AO /

Spec. Ref.

06.2 damp litmus paper 1 AO1

4.8.2.4

AO /

Spec. Ref.

06.3 1 AO1

4.7.2.2

AO /

Spec. Ref.

06.4 1 AO2

4.7.3.1

– – –

AO /

Spec. Ref.

06.5 1.5 × 10 0.9 × 10 1 AO2

4.7.3.1

(ratio =) 15 : 9 1

= 5 : 3 allow correct determination of 1

the simplest whole number ratio

from an attempt at a density

ratio

alternative approach

(ratio =) 17

1.5 0.9

(1)

0.9 0.9

1.666 : 1 (1)

= 5 : 3 (1) allow correct determination of

the simplest whole number ratio

from an attempt at a density

ratio

AO /

Spec. Ref.

06.6 the pipes will melt 1 AO3

or 4.7.3.1

the polymers will melt allow the melting point of both–– – 4.10.3.3

polymers is below 300°C

AO /

Spec. Ref.

06.7 oil is non-renewable allow oil is finite 1 AO2

or 4.10.1.1

paper is obtained from a

renewable source

Total Question 6 9

How to answer it

Alkenes, Addition Reactions & Polymers

📋 What this question tests

This 9-mark question assesses fundamental organic chemistry and practical skills from Topics 7, 8, and 10:

Alkene functional group: The C=C double bond and the standard bromine water test for unsaturation.
Gas identification: Chemical test for chlorine gas.
Addition reactions: How halogen molecules react across a carbon-carbon double bond.
Addition polymerisation: Identifying the repeating unit of a polymer from its monomer.
Mathematical skills: Simplifying decimal numbers into a simplest whole-number ratio.
Evaluating materials: Linking thermal properties (melting points) and sustainability (renewable vs non-renewable resources) to real-world uses.

Question 06.1 • 1 Mark

Test for Unsaturation (Alkenes)

Bromine water colour change

✅ Correct Answer

colourless

1 Mark: Awarded for writing "colourless".

❌ Common Errors

Writing "clear" instead of "colourless". A solution can be clear (see-through) but still have a colour (e.g. clear orange). The mark scheme explicitly notes "ignore clear".
Writing "white" or "discoloured".

💡 Key Knowledge

Bromine water (Br₂) is naturally orange / brown. When shaken with an unsaturated hydrocarbon (an alkene with a C=C bond), an addition reaction occurs, forming a colourless dibromoalkane. Alkanes (saturated) do not react and remain orange.

Question 06.2 • 1 Mark

Gas Identification: Chlorine

Selecting the correct testing reagent

✅ Correct Answer

Tick box 2: Damp litmus paper

1 Mark: Exactly one box ticked for damp litmus paper.

🧠 Exam Technique: Gas Tests Recall

Damp litmus paper: Chlorine bleaches it white (turns red momentarily first).
Lighted splint: Used for Hydrogen (gives a squeaky pop).
Limewater: Used for Carbon Dioxide (turns milky/cloudy).

Question 06.3 • 1 Mark

Addition Reaction of Halogens

Displayed structural formula of ethene + chlorine

✅ Correct Answer

Tick box 2 (the middle option):

   Cl  Cl
    |   |
H — C — C — H
    |   |
   H   H

1 Mark: 1,2-dichloroethane structure selected.

💡 How Addition Reactions Work

In an addition reaction, the double bond ( C=C ) opens up into a single covalent bond ( C—C ).
Each carbon atom gets one new chlorine atom attached to it.
Box 1 only added one Cl atom (incorrect formula). Box 3 added three Cl atoms (incorrect stoichiometry).

Question 06.4 • 1 Mark

Structure of Addition Polymers

Identifying the repeating unit of poly(chloroethene)

✅ Correct Answer

Tick box 1 (the top option):

  ( H   Cl )
  ( |   |  )
—(— C — C —)—
  ( |   |  ) n
  ( H   H  )

1 Mark: Correct repeating unit with 3 hydrogens and 1 chlorine.

🧠 Exam Technique: Monomer to Polymer

Check the atoms on the monomer: Chloroethene has 3 H atoms and 1 Cl atom.
The polymer must have the exact same ratio of atoms.
Opening the C=C double bond gives single C—C bonds extending through the brackets with subscript n .

Question 06.5 • 3 Marks

Simplest Whole Number Ratio Calculation

poly(chloroethene) density : poly(ethene) density

📐 Step-by-Step Calculation

From Table 3: Density of poly(chloroethene) = 1.5 g/cm³, Density of poly(ethene) = 0.9 g/cm³.

Eliminate decimals by multiplying both values by 10:
1.5 × 10 = 15 and 0.9 × 10 = 9
Ratio = 15 : 9 [1 mark]

Find the highest common factor (HCF):
Both 15 and 9 are divisible by 3:
15 ÷ 3 = 5 and 9 ÷ 3 = 3 [1 mark]

Write the final simplified whole number ratio:
Simplest whole number ratio = 5 : 3 [1 mark]

Mark Breakdown (3 Marks Total):
• 1 mark for multiplying to eliminate decimals ( 1.5 × 10 : 0.9 × 10 )
• 1 mark for the unsimplified ratio ( 15 : 9 )
• 1 mark for the simplest whole number ratio ( 5 : 3 )

❌ Common Errors to Avoid

Reversing the order: Giving 3 : 5 instead of 5 : 3. Always check which substance comes first in the question!
Leaving as decimals: Writing 1.67 : 1 or 1.5 : 0.9 is not a whole number ratio.

Question 06.6 • 1 Mark

Evaluating Material Suitability

Why neither polymer is suitable for 300 °C steam pipes

✅ Acceptable Answers (Any one)

The pipes / polymers will melt.
The melting point of both polymers is below 300 °C.

1 Mark: Clear reference to the polymers melting or operating above their melting points.

🧠 Exam Technique: Use the Provided Data

The question explicitly says "Use Table 3". Table 3 shows melting temperatures are 260 °C and 120 °C. Because 300 °C is higher than both melting temperatures, they cannot hold hot steam without melting and failing.

Question 06.7 • 1 Mark

Sustainability & Raw Materials

Why paper bags are more sustainable than poly(ethene)

✅ Acceptable Answers (Any one)

(Crude) oil is non-renewable / finite.
Paper / wood / trees is a renewable resource (trees can be replanted).

1 Mark: Correct comparison stating crude oil is finite/non-renewable OR paper is renewable.

❌ Common Errors

Focusing only on litter or recycling (e.g. "paper decomposes faster") when the prompt specifically directs you to the raw materials: "Poly(ethene) is produced from crude oil. Paper is produced from trees."
Vague words like "natural" or "eco-friendly" instead of precise GCSE terms like renewable or non-renewable / finite.

Topics

Chemistry · C7: Organic Chemistry · C8: Chemical Analysis · C10: Using Resources

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 2 (Foundation), June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.