AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Atmospheric pollutants from fuels: The combustion of fuels is a major source of atmospheric pollutants.
When fuels burn, the elements inside them react with oxygen and release gases into the atmosphere.
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
When fuels burn, the elements inside them react with oxygen and release gases into the atmosphere. Carbon in the fuel forms carbon dioxide, which is a greenhouse gas. Hydrogen forms water vapour. If the fuel contains sulfur impurities, sulfur dioxide is produced, and this can dissolve in rain to form acid rain. At high temperatures in engines, nitrogen and oxygen from the air react to form nitrogen oxides, which also contribute to acid rain and to photochemical smog. Incomplete combustion, caused by too little oxygen, produces carbon monoxide, a toxic gas, and solid particles called particulates, which can cause breathing problems and reduce visibility. A balanced equation such as CH₄ + 2O₂ → CO₂ + 2H₂O shows complete combustion, while limited oxygen gives CO instead of CO₂.
What earns the marks
- States that burning fuels releases gases into the atmosphere, making combustion a major pollution source.
- Names carbon dioxide as a product of complete combustion and links it to the greenhouse effect.
- Names sulfur dioxide from sulfur impurities and links it to acid rain.
- Names nitrogen oxides formed at high temperature and links them to acid rain or smog.
- Names carbon monoxide and particulates from incomplete combustion and gives a harmful effect of each.
- Uses a word or balanced symbol equation to show complete or incomplete combustion.
Common mistakes and how to put them right
Saying carbon dioxide causes acid rain.
Put it right: Sulfur dioxide and nitrogen oxides are the acidic gases; carbon dioxide is a greenhouse gas.
Writing that carbon monoxide is produced when there is plenty of oxygen.
Put it right: Carbon monoxide forms during incomplete combustion when oxygen is limited.
Confusing particulates with gases.
Put it right: Particulates are tiny solid particles, often carbon, released in smoke.
Exam tips
- Link each pollutant to its source and its effect in a three-part chain: fuel, gas, consequence.
- Use correct names and formulae, for example CO₂, SO₂, NOₓ and CO, and balance any equation you write.
- If asked to evaluate, compare pollutants by harm, for example carbon monoxide is toxic while carbon dioxide contributes to climate change.
- Read the question carefully: 'atmospheric pollutants' means gases and particles released into the air, not waste left in the engine.
Try the lesson
The start of the Atmospheric pollutants from fuels: The combustion of fuels is a major source of atmospheric pollutants. lesson, made from checked teaching notes for this specification point.
Have a go first
Which gas is produced from the carbon in a hydrocarbon fuel when it burns in a plentiful supply of air?
Listen
When fuels burn, the elements inside them react with oxygen and release gases into the atmosphere. Carbon in the fuel forms carbon dioxide, which is a greenhouse gas. Hydrogen forms water vapour. If the fuel contains sulfur impurities, sulfur dioxide is produced, and this can dissolve in rain to form acid rain. At high temperatures in engines, nitrogen and oxygen from the air react to form nitrogen oxides, which also contribute to acid rain and to photochemical smog. Incomplete combustion, caused by too little oxygen, produces carbon monoxide, a toxic gas, and solid particles called particulates, which can cause breathing problems and reduce visibility. A balanced equation such as CH₄ + 2O₂ → CO₂ + 2H₂O shows complete combustion, while limited oxygen gives CO instead of CO₂. A strong answer earns marks for these points. States that burning fuels releases gases into the atmosphere, making combustion a major pollution source. Names carbon dioxide as a product of complete combustion and links it to the greenhouse effect. Names sulfur dioxide from sulfur impurities and links it to acid rain. Names nitrogen oxides formed at high temperature and links them to acid rain or smog. A common slip: Saying carbon dioxide causes acid rain. Instead, sulfur dioxide and nitrogen oxides are the acidic gases; carbon dioxide is a greenhouse gas. Exam tip: Link each pollutant to its source and its effect in a three-part chain: fuel, gas, consequence.
Key words
Say what each word means before you turn the card.
Complete combustion
Try answering aloud or in your head before turning the card.
Incomplete combustion
Try answering aloud or in your head before turning the card.
Acid rain
Try answering aloud or in your head before turning the card.
See every definition
- Complete combustion
- Burning a fuel with enough oxygen, producing carbon dioxide and water vapour.
- Incomplete combustion
- Burning a fuel with too little oxygen, producing carbon monoxide and solid particles called particulates.
- Acid rain
- Formed when sulfur dioxide or nitrogen oxides dissolve in rain.
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