# Describe two differences between complete combustion and incomplete combustion of a hydrocarbon fuel. For each difference, state what is produced and explain how availability of oxygen causes that difference.

> Cambridge International IGCSE Chemistry (0620) — 11.3 Fuels · Describe · 4 marks

## Mark scheme (4 marks)

1. Complete combustion produces carbon dioxide / CO₂; incomplete combustion produces carbon monoxide / CO and/or carbon (soot)
2. Complete combustion occurs when there is a plentiful/excess supply of oxygen; incomplete combustion occurs when oxygen supply is limited/insufficient
3. Both complete and incomplete combustion produce water / H₂O
4. Complete combustion releases more energy than incomplete combustion (because the fuel is fully oxidised)

## Key terms

- [complete combustion](https://www.gradenine.co.uk/glossary/complete-combustion)
- [incomplete combustion](https://www.gradenine.co.uk/glossary/incomplete-combustion)
- [hydrocarbon](https://www.gradenine.co.uk/glossary/hydrocarbon)

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-two-differences-between-complete-combustion-d594908f) · Published by Druglandscape Ltd.