AQA GCSE Combined Science: Trilogy Chemistry Paper 2 (Foundation), 2021: Question 2
10 marks · Standard Demand difficulty · Short Answer
Analyze data on car energy sources and nitrogen dioxide concentrations, perform calculations, and identify properties of catalysts and resources.
Practise this questionQuestion
Question text
02 Cars cause atmospheric pollution.
02.1 Figure 2 shows the percentage of cars in the UK using different energy sources.
Figure 2
The percentage of cars using petrol is 54%.
Draw the bar for petrol on Figure 2.8
[1 mark]
Some car emissions contain nitrogen dioxide.
Table 1 shows the concentration of nitrogen dioxide in the air in three different areas
for 1 week.
Table 1
Concentration of nitrogen dioxide in the air
in arbitrary units
Day City centre Countryside Motorway
Monday 35 8 22
Tuesday 37 8 23
Wednesday 37 8 23
Thursday 34 8 23
Friday 37 8 23
Saturday 29 7 20
Sunday 22 6 17
02.2 Which column of data has the greatest range?
[1 mark]
Tick ( ) one box.
City centre
Countryside
Motorway 9
02.3 Explain why the concentration of nitrogen dioxide in the air is lower on Sunday.
[2 marks]
02.4 Calculate the mean value for the concentration of nitrogen dioxide in the air in the
city centre for the days from Monday to Friday.
Use Table 1.
[2 marks]
Mean value for concentration of nitrogen dioxide = arbitrary units
Nitrogen dioxide is removed from car emissions by catalytic converters.
02.5 Which two of the following are correct statements about catalysts?
[2 marks]
Tick ( ) two boxes.
Catalysts are included in the chemical equation for a reaction.
Catalysts are not used up in a reaction.
Catalysts decrease the surface area of the reactants.
Catalysts increase the concentration of the reactants.
Catalysts lower the activation energy of a reaction.
02.6 The catalyst in catalytic converters contains platinum.
Platinum is an unreactive metal obtained from the Earth’s crust.
Complete the sentence.
Choose the answer from the box.
[1 mark]
finite resource formulation renewable resource
Platinum is a 11 .
02.7 Emissions from cars that burn fossil fuels contain carbon dioxide.
What is used to test for carbon dioxide?
[1 mark]
Tick ( ) one box.
Burning splint
Glowing splint
*10* Limewater
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
02.1 bar drawn to 54 (%) allow a tolerance of ± ½ a small 1 AO2
square 5.9.3.1
02.2 city centre 1 AO3
5.3.1.4
5.9.3.1
02.3 less traffic allow fewer lorries / cars 1 AO3
5.9.3.1
(because) fewer people working allow (because) no school 1
allow (because) businesses /
factories closed
35 + 37 + 37 + 34 + 37 1 AO2
02.4 (mean =)
5.9.3.1
= 36 (arbitrary units) 1
02.5 catalysts are not used up in a 1 AO1
reaction 5.6.1.4
catalysts lower the activation
energy of a reaction 1
02.6 finite resource 1 AO2
5.8.1.2
5.10.1.1
02.7 limewater 1 AO1
5.8.2.3
Total 10
How to answer it
Atmospheric Pollution and Car Emissions
What this question tests
This question assesses your ability to interpret data from graphs and tables, perform basic statistical calculations (mean and range), and recall fundamental chemistry facts about catalysts, resources, and gas tests.
Drawing Data on a Bar Chart
Exam Technique
On the graph, each large square represents 10 units, and there are 5 small squares within it. This means 1 small square = 2 units.
To draw 54%, go to the 50 line and count up exactly 2 small squares.
Correct Answer
A bar for "Petrol" drawn to the height of 54. The examiner allows a tiny tolerance of half a small square.
Identifying the Greatest Range
Calculation Steps
- City Centre: 37 - 22 = 15
- Countryside: 8 - 6 = 2
- Motorway: 23 - 17 = 6
Correct Answer
City centre
1 Mark: For correctly identifying the column with the largest difference between max and min values.
Explaining Data Trends
Key Knowledge
Nitrogen dioxide (NO₂) is a pollutant primarily produced by internal combustion engines in cars. Therefore, NO₂ levels are directly linked to traffic volume.
Correct Answer
- There is less traffic / fewer cars on Sunday.
- Because fewer people are working (or schools/factories are closed).
2 Marks: One for the observation (less traffic), one for the reason (no work/school).
Calculating the Mean
Step-by-Step Calculation
- Identify the correct data: Use only the "City centre" column and only the days "Monday to Friday".
35, 37, 37, 34, 37 - Add the values: 35 + 37 + 37 + 34 + 37 = 180
- Divide by the number of values: 180 ÷ 5 = 36
Final Answer
36 arbitrary units
Common Error
Students often lose marks by including Saturday and Sunday in the calculation. Always read the date range in the question carefully!
Properties of Catalysts
Key Knowledge
A catalyst speeds up a reaction without being used up. It does this by providing an alternative pathway with a lower activation energy.
Correct Answers
- Catalysts are not used up in a reaction.
- Catalysts lower the activation energy of a reaction.
Examiner Insight
Top students remember that catalysts are not written as reactants in a chemical equation; they are usually written above the reaction arrow.
Resources and Gas Tests
02.6: Resources
Platinum is a finite resource. This means it is being used up faster than it can be replaced and will eventually run out.
02.7: Gas Testing
The standard test for Carbon Dioxide (CO₂) is Limewater. If CO₂ is present, the limewater turns cloudy/milky.
Don't Mix Up Your Splints!
- Glowing splint: Tests for Oxygen (relights).
- Burning splint: Tests for Hydrogen (squeaky pop).
- Limewater: Tests for Carbon Dioxide.
Topics
Chemistry · C6: The Rate and Extent of Chemical Change · C8: Chemical Analysis · C9: Chemistry of the Atmosphere · C10: Using Resources
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 2 (Foundation), 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.