What is the difference between complete and incomplete combustion? 

Complete combustion happens when there is plenty of oxygen and all of the fuel is burned completely.


Incomplete combustion happens when there is limited oxygen and can result in the production of pollutants.

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What pollutants can incomplete combustion produce? 

  1. Carbon (soot).
  2. Carbon monoxide.
  3. Unburnt hydrocarbons.

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How is soot in the air harmful? 

Soot is a particulate.

  1. If inhaled, it can get stuck in our lungs and cause damage, leading to respiratory problems.
  2. It also cause smog / global dimming - the particles, and the clouds they help produce, reflect sunlight back into space so less light reaches earth.

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Why is carbon monoxide dangerous?

  1. It binds to haemoglobin, so less oxygen is transported around the body.
  2. Lack of oxygen causes fainting, a coma, or even death.
  3. It also has no smell or colour so it's hard to detect.

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How can the combustion of fossil fuels form sulfur dioxide? 

Some fossil fuels contain sulfur impurities - so when the fossil fuel is combusted, the sulfur becomes oxidised into sulfur dioxide.

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How can the combustion of fossil fuels form nitrogen oxides? 

Combustion takes place in engines at high temperatures and pressures.


These conditions allow nitrogen and oxygen from the air to react together and form nitrogen oxides.

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How does acid rain form?

Nitrogen oxides and sulfur dioxide can dissolve in the water vapour in the atmosphere, forming dilute nitric or sulfuric acid, which falls as acid rain.

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What are 3 negative effects of acid rain?

  1. Kills plants.
  2. Damages buildings.
  3. Corrodes statues.

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