IGCSE Chemistry 0620 · Chemistry of the environment · 10.3

Air quality and climate: past paper questions

97 real questionsasked in 8 of the last 10 exam series2019–2026usually: State, Which, Draw, Suggest, Describe

Real questions on air quality and climate

The newest 20 of 97 written questions. Open one to see it on the real paper.

0620/31 · May/June 2026 · Q7b(i)[1]
State one source of sulfur dioxide in the air.
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0620/31 · May/June 2026 · Q7b(ii)[1]
State one adverse effect of sulfur dioxide in the air. (ii)
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0620/31 · May/June 2026 · Q7b(iii)[1]
Oxides of nitrogen are also air pollutants. They form acids when they dissolve in water. Choose the pH value that is acidic. Draw a circle around your chosen answer. pH 3 pH 7 pH 10 pH 14 (iii)
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0620/32 · February/March 2026 · Q1a[1]
is approximately 78% of clean, dry air
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0620/32 · February/March 2026 · Q1g[1]
is a product of photosynthesis
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0620/32 · February/March 2026 · Q1i[1]
is a gas needed for iron to rust.
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0620/32 · February/March 2026 · Q5b[2]
State why phosphates and some metal compounds found in river water are harmful. phosphates metal compounds (b) Water from natural sources can be polluted with harmful substances.
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0620/32 · February/March 2026 · Q5c(ii)[2]
State two adverse effects of nitrogen dioxide in air.
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0620/32 · October/November 2025 · Q4g(ii)[1]
State one adverse effect to the environment of the production of carbon dioxide.
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0620/33 · October/November 2025 · Q3c(i)[1]
The water contains harmful microbes. Suggest a source of the microbes in the water.
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0620/33 · October/November 2025 · Q3c(ii)[1]
State how the water is treated so that the microbes do not cause harm to people.
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0620/33 · October/November 2025 · Q3d[1]
Before the treatment in (c)(ii), the water has a bad taste and odour. State the name of a substance that is added to remove the bad taste and odour from the water.
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0620/33 · October/November 2025 · Q6c(i)[2]
State the adverse effect that increased levels of sulfur dioxide have on the environment.
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0620/33 · October/November 2025 · Q6c(ii)[1]
Increased levels of carbon dioxide in the atmosphere can lead to increased global warming. State one strategy which would help to remove carbon dioxide that is already in the atmosphere.
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0620/31 · May/June 2025 · Q8d[1]
A sample of polluted air contains carbon monoxide and methane. carbon monoxide State one harmful effect of each of these air pollutants.
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0620/32 · May/June 2025 · Q8c(i)[2]
State one harmful effect of each of these air pollutants. sulfur dioxide
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0620/32 · May/June 2025 · Q8c(ii)[2]
Describe how flue gas desulfurisation reduces emissions of sulfur dioxide gas.
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0620/33 · May/June 2025 · Q4b(i)[1]
State one source of oxides of nitrogen in the air.
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0620/33 · May/June 2025 · Q7c[2]
A sample of air contains carbon dioxide and oxides of nitrogen. State one harmful effect of each of these air pollutants. carbon dioxide
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0620/41 · May/June 2025 · Q1d[1]
is produced by the decomposition of vegetation
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What examiners said

Comprehensive responses • Most candidates knew that nitrogen is approximately 78 percent of clean, dry air.
— Examiner report, February/March 2026, 0620/32 Q1(a) (Cambridge)

Comprehensive responses • Most candidates knew a product of photosynthesis.
— Examiner report, February/March 2026, 0620/32 Q1(g) (Cambridge)

Comprehensive responses • A few candidates knew the correct reasons for why the given substances were harmful in river water. ‘Phosphates in the deoxygenation of water’ and ‘metal compounds being toxic or poisonous’ were good answers. Limited responses • A few candidates knew one correct reason only. • Many candidates did not know any correct reasons. ‘Kills marine life’ and ‘causing rusting for...
— Examiner report, February/March 2026, 0620/32 Q5(b) (Cambridge)

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In the syllabus

10.3 Air quality and climate

State the composition of clean, dry air as approximately 78% nitrogen, N2, 21% oxygen, O2 and the remainder as a mixture of noble gases and carbon dioxide, CO2
State the source of each of these air pollutants, limited to: (a) carbon dioxide from the complete combustion of carbon-containing fuels (b) carbon monoxide and particulates from the incomplete combustion of carbon- containing fuels (c) methane from the decomposition of vegetation and waste gases from digestion in animals (d) oxides of nitrogen from car engines (e) sulfur dioxide from the combustion of fossil fuels which contain sulfur compounds
State the adverse effect of these air pollutants, limited to: (a) carbon dioxide: higher levels of carbon dioxide leading to increased global warming, which leads to climate change (b) carbon monoxide: toxic gas (c) particulates: increased risk of respiratory problems and cancer (d) methane: higher levels of methane leading to increased global warming, which leads to climate change (e) oxides of nitrogen: acid rain, photochemical smog and respiratory problems (f) sulfur dioxide: acid rain
State and explain strategies to reduce the effects of these environmental issues, limited to: (a) climate change: planting trees, reduction in livestock farming, decreasing use of fossil fuels, increasing use of hydrogen and renewable energy, e.g. wind, solar (b) acid rain: use of catalytic converters in vehicles, reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas desulfurisation with calcium oxide
Describe photosynthesis as the reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light
State the word equation for photosynthesis, carbon dioxide + water → glucose + oxygen
Describe how the greenhouse gases carbon dioxide and methane cause global warming, limited to: (a) the absorption, reflection and emission of thermal energy (b) reducing thermal energy loss to space
Explain how oxides of nitrogen form in car engines and describe their removal by catalytic converters, e.g. 2CO + 2NO → 2CO2 + N2
State the symbol equation for photosynthesis, 6CO2 + 6H2O → C6H12O6 + 6O2

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