AQA GCSE Combined Science: Trilogy Chemistry Paper 2 (Foundation), June 2025: Question 4
14 marks · Low Demand difficulty · Short Answer
Answer questions on potable water, waste water treatment, comparing poly(propene) and wool, recycling, and the cracking and testing of alkenes.
Practise this questionQuestion
Question text
04 Humans use many different resources.
Water is an important natural resource.
04.1 What is meant by ‘potable water’?
[1 mark]
Tick ( ) one box.
Water from the ground
Water that is pure
Water that is safe to drink
04.2 Waste water needs treatment before the water is put back into rivers and the sea.
The first stage of waste water treatment is to pass the waste water through
metal grids.
Why is the waste water passed through metal grids?
[1 mark]
Tick ( ) one box.
To remove dissolved salts
To remove large solid objects
To remove microbes
To remove oxygen gas
Clothes can be made from different materials.
Some clothes are made from wool and some clothes are made from poly(propene).
04.3 One sheep produces 4.5 kg of wool.
50 g of wool is needed to make a hat.
Calculate the number of hats that can be made from the wool of one sheep.
1 kg = 1000 g
[3 marks]
17 Number of hats =
04.4 Table 4 gives information about poly(propene) and wool.
Table 4
Poly(propene) Wool
Source of material Crude oil Sheep
Level of insulation High Medium
Cost Low High
Durability High Medium
Explain the advantages of using poly(propene) and of using wool for clothing.
[4 marks]
Extra space
04.5 After being used, clothes can be:
• given to other people to wear
• used to make insulation blocks for buildings.
Complete the sentences.
Choose answers from the box.
[2 marks]
recycled reduced released reused reversed
When clothes are given to other people to wear,
the clothes are .
When clothes are used to make insulation blocks for buildings,
the clothes are .
Poly(propene) is made from an alkene.
Alkenes are produced by cracking alkanes.
04.6 A high temperature is used for cracking alkanes.
Which two of the following can also be used to crack alkanes?
[2 marks]
Tick ( ) two boxes.
A catalyst
A solvent
Carbon dioxide
Steam
Sulfuric acid
04.7 Which chemical is used to test for alkenes?
[1 mark]
Tick ( ) one box.
Ammonia
Bromine water
Copper sulfate
Nitrogen
Mark scheme
Show the mark scheme
Question 4
AO /
Question Answers Extra information Mark
Spec. Ref.
04.1 water that is safe to drink 1 AO1
5.10.1.2
AO /
Spec. Ref.
04.2 to remove large solid objects 1 AO1
5.10.1.3
AO /
Spec. Ref.
04.3 (conversion 4.5 kg =) 4500 (g) 1 AO2
5.10.1.1
4500 allow correct use of incorrect /
(number of hats =) 1
50 no conversion
= 90 1
alternative approach
(conversion 50 g =) 0.05 (kg) (1)
4.5 allow correct use of incorrect /
(number of hats =) (1)
0.05 no conversion
= 90 (1) – – –
AO /
Question Answers Mark
Spec. Ref.
04.4 Level 2: Relevant points (reasons / causes) are identified, given in 3–4 AO3
detail and logically linked to form a clear account 5.10.1.1
Level 1: Points are identified and stated simply, but their relevance 1–2
is not clear and there is no attempt at logical linking.
No relevant content 0
Indicative content
(poly(propene) has)
• higher level of insulation
o (so) keeps the wearer warmer
• lower cost
o (so) the clothes are cheaper
• higher durability
o (so) the clothes last longer
(wool is)
• sheep are a renewable resource
o so are sustainable
for Level 2 there must be an advantage for both poly(propene) and
wool plus a linked explanation
AO /
Spec. Ref.
04.5 must be in this order AO2
5.10.2.2
reused 1
recycled – – 1 –
AO /
Spec. Ref.
04.6 a catalyst 1 AO1
5.7.1.4
steam 1
14 AO /
Spec. Ref.
04.7 bromine water 1 AO1
5.7.1.4
Total Question 4 14
How to answer it
Earth's Resources, Water Treatment & Polymers
What this question tests
This 14-mark question tests core recall and application from AQA GCSE Combined Science: Trilogy (Chemistry Paper 2):
- Potable water vs pure water: Defining potable water correctly.
- Waste water treatment: Screening and grit removal using metal grids.
- Quantitative skills: Metric unit conversion (kg to g) and multi-step ratio calculations.
- Evaluating materials & sustainability: Comparing synthetic polymers (from crude oil) with natural materials (wool).
- Reducing resource use: Distinguishing between reusing and recycling.
- Hydrocarbon chemistry: Cracking conditions (steam and catalysts) and testing for alkenes using bromine water.
Definition of Potable Water
AQA Specification 5.10.1.2
✅ Correct Answer
Water that is safe to drink (box 3)
💡 Key Knowledge
Potable water is not chemically pure water! It contains safe, low levels of dissolved minerals and salts, and has no harmful microbes.
❌ Common Error
Do not confuse "pure" with "potable"! Pure water contains strictly 100% H₂O molecules with zero dissolved solutes. Bottled mineral water is potable, but chemically impure.
Waste Water Treatment: Metal Grids
AQA Specification 5.10.1.3
✅ Correct Answer
To remove large solid objects (box 2)
💡 Key Knowledge
The first stage of sewage treatment is screening. Metal grids filter out large debris such as twigs, leaves, plastics, and wipes before sedimentation.
🧠 Exam Technique
Think about scale: dissolved salts and bacteria (microbes) pass straight through metal mesh grids; only large physical solids get trapped.
Unit Conversion & Mass Calculation
AQA Specification 5.10.1.1
📐 Step-by-Step Calculation
- Step 1: Convert units so they match (kg to g)
Mass of wool from one sheep = 4.5 kg
4.5 kg × 1000 = 4500 g [1 mark] - Step 2: Divide total mass available by mass per hat
Number of hats = 4500 ÷ 50 [1 mark] - Step 3: State the final answer
Number of hats = 90 [1 mark]
❌ Common Trap
Dividing 50 ÷ 4.5 = 11.1 without converting units! Always make sure your units match before calculating.
🧠 Exam Technique
Show every line of working. If you make an arithmetic slip, the examiner can still award error carried forward (ecf) marks if the method is visible.
Evaluating Materials: Poly(propene) vs Wool
AQA Specification 5.10.1.1 (Level of Response)
| Property | Poly(propene) | Wool |
|---|---|---|
| Source | Crude oil | Sheep |
| Insulation | High | Medium |
| Cost | Low | High |
| Durability | High | Medium |
✅ Model Full-Mark Answer (Level 2, 4 Marks)
- Advantage of poly(propene): It has higher insulation, so it keeps the wearer warmer. It also costs less, making the clothes cheaper to buy, and has higher durability, so garments last longer without wearing out.
- Advantage of wool: Wool comes from sheep, which is a renewable resource, meaning it is more sustainable and does not deplete finite fossil fuels like crude oil.
🧠 Examiner Insight: How to Score Level 2 (3–4 marks)
- You must give an advantage of poly(propene) AND an advantage of wool.
- You must include a linked explanation ("which means...", "so that..."). Simply quoting the table (e.g. "poly(propene) has high insulation") only scores Level 1 (1–2 marks).
Reusing vs Recycling
AQA Specification 5.10.2.2
✅ Correct Sentences
When clothes are given to other people to wear, the clothes are reused. [1 mark]
When clothes are used to make insulation blocks for buildings, the clothes are recycled. [1 mark]
💡 The Difference
Reusing: Using an item again for its original purpose without reprocessing it.
Recycling: Breaking down or reprocessing a waste material into an entirely new product.
Methods of Cracking Alkanes
AQA Specification 5.7.1.4
✅ Correct Answers (Choose 2)
- A catalyst (box 1) [1 mark]
- Steam (box 4) [1 mark]
💡 The Two Types of Cracking
Cracking is thermal decomposition that breaks long-chain alkanes into smaller, more useful molecules:
- Catalytic cracking: High temperature + hot aluminium oxide / zeolite catalyst.
- Steam cracking: High temperature + mixed with steam.
Chemical Test for Alkenes
AQA Specification 5.7.1.4
✅ Correct Answer
Bromine water (box 2) [1 mark]
💡 Key Knowledge & Colour Change
When shaken with an alkene (contains a C=C double bond):
Bromine water turns from orange-brown to colourless.
With an alkane (saturated), there is no reaction and bromine water stays orange-brown.
❌ Word Choice Alert
Examiners reject "turns clear". Solutions can be clear and orange. You must say colourless or decolourised.
Topics
Chemistry · C10: Using Resources · C7: Organic Chemistry
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 2 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.