AQA GCSE Chemistry Chemistry Paper 2 (Higher), 2024: Question 8
13 marks · Standard Demand difficulty · Short Answer
This multi-part question assesses knowledge of organic functional groups, chemical testing, combustion reactions, polymerisation, and the properties of polymers.
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Question text
08 This question is about monomers and polymers.
Compound A has an alkene functional group and an ester functional group.
Figure 8 represents a molecule of compound A.
Figure 8
08.1 Draw a circle around the alkene functional group on Figure 8.
[1 mark]
08.2 Describe what will be seen when compound A is shaken with bromine water.
[2 marks]
08.3 Figure 9 is a repeat of Figure 8.
Figure 9
Draw a circle around the ester functional group on Figure 9.
[1 mark]
08.4 Compound A has the formula C4H6O2
Compound A is flammable.
Write a balanced equation for the complete combustion of compound A.
[3 marks]
+ 31 → +
08.5 Many molecules of compound A join together to form polymer B.
Complete the displayed formula equation which represents this reaction.
[2 marks]
08.6 What type of polymer is polymer B?
[1 mark]
Tick ( ) one box.
Addition polymer
Condensation polymer
DNA
Protein 32
Polymer B is a polymer which melts when heated.
08.7 What word is used to describe polymers which melt when heated?
[1 mark]
08.8 Explain why some polymers do not melt when heated.
[2 marks]
Mark scheme
Show the mark scheme
Question 8
AO /
Question Answers Extra information Mark
Spec. Ref.
08.1 1 AO2
4.7.2.1
AO /
Spec. Ref.
08.2 orange (bromine water) allow yellow / brown 1 AO2
4.7.1.4
turns colourless allow is decolourised 1
ignore clear
AO /
Spec. Ref.
08.3 1 AO3
4.7.2.4
4.7.3.2
– – –
AO /
Spec. Ref.
08.4 2 C4H6O2 + 9 O2→8 CO2 + 6 H2O allow multiples 3 AO2
4.7.2.1
4.1.1.1
allow 1 mark for 4.3.1.1
C4H6O2 + O2 → 4.7.2.1 25
with incorrect / no multipliers
4.7.2.4
allow 1 mark for
→ CO2 + H2O
with incorrect / no multipliers
ignore state symbols
AO /
Spec. Ref.
08.5 single C-C bond in polymer do not accept extra atoms 1 AO2
repeating unit added to trailing bonds 4.7.3.1
n after polymer repeating unit 1
an answer of
scores 2 marks– – –
AO /
Spec. Ref.
08.6 addition polymer 1 AO2
4.7.3.1
AO /
Spec. Ref.
08.7 thermosoftening allow thermoplastic 1 AO1
4.10.3.3
AO /
Spec. Ref.
08.8 cross-links between (polymer) allow covalent bonds between 1 AO1
chains (polymer) chains 4.2.2.5
4.10.3.3
(so) too much energy needed to allow (so) too much energy 1
overcome the cross-links needed to overcome the
covalent bonds between
(polymer) chains
Total Question 8 13
How to answer it
Monomers, Polymers, and Organic Reactions
What this question tests
This question assesses your ability to identify functional groups in organic molecules, describe the chemical test for unsaturation, balance complex combustion equations, and understand the structure and properties of addition polymers.
Identifying Functional Groups
Recognising Alkenes and Esters
💡 Key Knowledge
- Alkene: Contains a Carbon-to-Carbon double bond ( C=C ).
- Ester: Contains the functional group -COO- (a carbon double-bonded to one oxygen and single-bonded to another).
🧠 Exam Technique
When asked to "draw a circle around the group," make sure your circle includes only the atoms involved in that specific functional group. Don't be messy!
✅ Correct Answers
08.1: Circle the C=C double bond at the top of the molecule.
08.3: Circle the O=C-O section in the middle of the molecule.
The Bromine Water Test
Testing for Unsaturation
✅ Correct Answer
The solution turns from orange to colourless.
❌ Common Errors
Never use the word "clear" to describe the final result. A solution can be clear but still have a colour (like apple juice). You must use the word "colourless".
🧠 Exam Technique
For "describe what is seen" questions, always give the initial colour and the final colour to ensure you get both marks.
Complete Combustion
Balancing Equations
📐 Calculation: Step-by-Step Balancing
Equation: C₄H₆O₂ + O₂ → CO₂ + H₂O
- Carbon: 4 carbons on the left means we need 4 CO₂ .
- Hydrogen: 6 hydrogens on the left means we need 3 H₂O (because 3 × 2 = 6).
- Oxygen: Count the right side: (4 × 2) + 3 = 11 oxygens.
- Balance Oxygen: The fuel (C₄H₆O₂) already has 2 oxygens. We need 9 more. This means 4.5 O₂ .
- Whole Numbers: Double everything to get whole numbers.
✅ Final Balanced Equation
2 C₄H₆O₂ + 9 O₂ → 8 CO₂ + 6 H₂O
Addition Polymerization
From Monomer to Polymer
💡 Key Knowledge
In addition polymerization, the C=C double bond "opens up" to form single bonds that connect to the next monomer. No other atoms are lost or gained.
🧠 Drawing the Polymer
- Change the C=C to C-C .
- Draw "extension bonds" through the brackets.
- Place a small n at the bottom right.
✅ Correct Answers
08.5: The diagram should show a single bond between the two carbons and an n outside the bracket.
08.6: Addition polymer.
Polymer Properties
Melting and Structure
✅ Correct Answers
08.7: Thermosoftening (or thermoplastic).
08.8: Some polymers do not melt because they have cross-links (covalent bonds) between the polymer chains. These require a lot of energy to break.
❌ Common Errors
Students often forget to mention energy. It isn't enough to say they have cross-links; you must explain that these bonds are strong and require large amounts of energy to overcome, which is why they don't melt/soften easily.
Topics
Chemistry · C7: Organic Chemistry · C2: Bonding, Structure and the Properties of Matter
Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 2 (Higher), 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.