AQA GCSE Combined Science: Trilogy Chemistry Paper 2 (Foundation), 2021: Question 3
9 marks · Standard Demand difficulty · Short Answer
Analyze the effects of climate change, describe and calculate trends in atmospheric carbon dioxide levels from a graph, and predict future levels.
Practise this questionQuestion
Question text
03 An increase in greenhouse gases in the Earth’s atmosphere causes an increase
in global temperature.
03.1 An increase in global temperature is a major cause of climate change.
Give two effects of global climate change.
[2 marks]
Carbon dioxide is a greenhouse gas.
Figure 3 shows the percentage of carbon dioxide in the Earth’s atmosphere
from 1750.
Figure 3
*0133.*2 Describe the trend in the percentage of carbon dioxide in the
Earth’s atmosphere from 1750 to 2000.
Use Figure 3.
[2 marks]
*14* Determine the change in the percentage of carbon dioxide in the
03.3
Earth’s atmosphere from 1950 to 2000.
Use Figure 3.
[2 marks]
Percentage of carbon dioxide in 1950
Percentage of carbon dioxide in 2000
Change in percentage of carbon dioxide = %
03.4 Give one reason why the percentage of carbon dioxide in the
atmosphere is changing.
[1 mark]
03.5 Predict the percentage of carbon dioxide in the Earth’s atmosphere in 2050.
You should extend the graph line on Figure 3.
[2 marks]
Percentage of carbon dioxide in 2050 = %
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
03.1 any two from: 2 AO1
• global warming 5.9.2.3
• melting polar ice caps
• rising sea levels
• flooding
• crop failure
or
famine
• extremes of weather
• loss of habitats
do not accept acid rain
do not accept global dimming
do not accept references to
ozone
ignore temperature rise
03.2 constant allow no change 1 AO2
allow stays same 5.9.2.2
(then) increases ignore values if given 1
03.3 (1950) 0.030 1 AO2
and 5.9.2.2
(2000) 0.036
(0.036 – 0.030)
= 0.006 (%) allow correct use of incorrectly 1
determined percentage
reading(s)
ignore + or –
03.4 any one from: 1 AO1
• combustion of fuel allow any named activity which 5.9.2.2
burns fuel
• deforestation
• population increase
03.5 extrapolation on graph 1 AO3
5.9.2.2
determine value from allow a value in the range 0.044 1
extrapolation at 2050 to 0.050
allow a tolerance of ± ½ a small
square
Total 9
How to answer it
Greenhouse Gases and Global Climate Change
What this question tests
This question assesses your ability to recall the environmental impacts of climate change, identify human activities that increase CO₂ levels, and demonstrate data skills including graph reading, calculating differences, and extrapolating trends.
Effects of Climate Change
✅ Correct Answers (Any two)
- Melting polar ice caps
- Rising sea levels
- Flooding
- Extreme weather (e.g., storms, droughts)
- Loss of habitats
- Crop failure or famine
❌ Common Errors
- Acid Rain: This is caused by sulfur dioxide, not greenhouse gases!
- Ozone Layer: Greenhouse gases do NOT "hole" the ozone layer.
- Global Dimming: Caused by particulates, not CO₂.
🧠 Exam Technique
The question states that temperature rise causes climate change. Therefore, simply writing "temperature rise" or "global warming" as an effect will not score marks. You must describe the consequences of that warming.
Describing Graph Trends
✅ Correct Answer
The percentage stayed constant (or no change) until roughly 1850, and then it increased.
💡 Key Knowledge
When a graph is a flat horizontal line, we describe the trend as "constant" or "stable". When it curves upwards, it is an "exponential increase".
Calculating Change
📐 Step-by-Step Calculation
- Find 1950 on the x-axis: Follow the line up to the curve and across to the y-axis.
Value = 0.030% - Find 2000 on the x-axis: Follow the line up to the curve and across to the y-axis.
Value = 0.036% - Calculate the difference: 0.036 - 0.030 = 0.006%
❌ Calculation Traps
Look closely at the y-axis scale. There are 5 small squares between 0.026 and 0.028. This means each small square represents 0.0004%. However, in this specific question, the points fall exactly on the major grid lines (0.030 and 0.036), making it easier to read.
Reasons for CO₂ Increase
✅ Correct Answers (Any one)
- Combustion of fossil fuels (e.g., driving cars, coal power stations)
- Deforestation (cutting down trees means less CO₂ is removed by photosynthesis)
- Increased population (leading to more energy use)
🧠 Examiner Commentary
Top-level responses use specific terms like combustion or deforestation. If you mention a specific activity like "burning peat" or "flying planes," you will still get the mark as these are examples of burning fuel.
Extrapolating Data
💡 What to Draw
To "extend the graph line," you should use a pencil to continue the curve of the line in the same direction it is already heading. Do not use a ruler to make a straight line if the existing trend is a curve!
✅ Prediction
Any value between 0.044% and 0.050% is acceptable, provided your drawn line matches your answer.
🧠 Exam Technique
You get 1 mark for the drawing and 1 mark for the value. Even if your drawing is slightly off, as long as you read the value from your own line correctly, you can often still get the second mark.
Topics
Chemistry · C9: Chemistry of the Atmosphere
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.