10.3.2 — Atmospheric Pollutants
Sources & Effects of Pollution — Papers 2 & 3 Style
Total Available
27 marks
15
Questions
3
Sections
Core
Level
🎯 Examiner's Note: In pollutant questions, the most common reason students lose marks is being too vague. "Cars pollute" is not an answer. Process + Source = Full marks.
State the source of carbon monoxide (CO) in the atmosphere.
⚠️ Trap: Don't just say 'cars'. The mark scheme wants the PROCESS — incomplete combustion.
Explain why carbon monoxide is toxic to humans.
⚠️ Trap: 'It stops you breathing' scores 0. The mark scheme wants the word HAEMOGLOBIN.
State TWO sources of methane (CH₄) in the atmosphere.
⚠️ Trap: 'Animals' alone scores 0. You must state the PROCESS — digestion, not just existence.
State why carbon dioxide (CO₂) is considered a pollutant even though it is naturally present in the atmosphere.
⚠️ Trap: You must link to ENHANCED greenhouse effect, not just 'greenhouse effect'.
Compare the conditions that lead to complete combustion versus incomplete combustion of a hydrocarbon fuel.
⚠️ Trap: 'Enough oxygen' is vague. Say 'excess oxygen' or 'sufficient / plentiful supply of oxygen'.
State the source of oxides of nitrogen (NOₓ) in the atmosphere and explain how they form.
⚠️ Trap: Say 'car engines' not just 'cars'. The HIGH TEMPERATURE is the key mechanism.
Explain how sulfur dioxide (SO₂) enters the atmosphere.
⚠️ Trap: Must say fossil fuels CONTAIN sulfur compounds — the sulfur is IN the fuel, not added separately.
Describe how acid rain is formed from sulfur dioxide and oxides of nitrogen in the atmosphere.
⚠️ Trap: 'They dissolve in rain' is incomplete. You must say they REACT WITH water to form ACIDS.
State TWO harmful effects of acid rain on the environment.
⚠️ Trap: 'It damages things' scores 0. Be specific — lakes, forests, buildings.
State ONE method used to reduce the emission of sulfur dioxide from power stations.
⚠️ Trap: 'Remove the sulfur' is too vague. Name the process — flue gas desulfurisation — or state it reacts with calcium oxide/limestone.
Name the solid pollutant formed during the incomplete combustion of a hydrocarbon fuel.
⚠️ Trap: Three acceptable answers — particulates, carbon, or soot. Any ONE scores the mark.
Write a word equation AND a balanced symbol equation for the incomplete combustion of methane (CH₄) to form carbon monoxide and water.
⚠️ Trap: Balance the equation carefully. Limited O₂ means CO, not CO₂.
Explain why particulates (soot) from incomplete combustion are harmful to human health.
⚠️ Trap: Must link to the RESPIRATORY SYSTEM. 'They are bad for you' scores 0.
A student claims: 'We should always burn fuels in a limited air supply to save oxygen.' Evaluate this statement using your knowledge of combustion products.
⚠️ This is a 3-mark evaluate question. You need: the correct point, the counter-argument, AND a conclusion.
Describe and explain the formation of THREE different atmospheric pollutants that result from the use of petrol-powered vehicles. For each, state the source and one harmful effect.
⚠️ Trap: Don't repeat pollutants. Name THREE distinct ones: CO, NOₓ, and particulates.
📚 Quick-Fire Pollutant Source Table
| Pollutant | Source / Formation | Key Harm |
|---|---|---|
| Carbon monoxide (CO) | Incomplete combustion of fuels | Binds to haemoglobin → reduces O₂ transport |
| Carbon dioxide (CO₂) | Complete combustion of fossil fuels | Enhanced greenhouse effect → global warming |
| Particulates / Soot | Incomplete combustion of fuels | Lodge in lungs → respiratory disease |
| Methane (CH₄) | Decomposition of vegetation; animal digestion | Greenhouse gas → global warming |
| Sulfur dioxide (SO₂) | Combustion of S-containing fossil fuels | Acid rain → kills aquatic life / forests |
| Oxides of nitrogen (NOₓ) | N₂ + O₂ react at high temp in car engines | Acid rain; photochemical smog |
Cambridge IGCSE Chemistry 0620 — Syllabus Topic 10.3.2
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