# Methane is the main hydrocarbon in natural gas and is used as a fuel in domestic boilers. State the products formed when methane undergoes complete combustion and explain why complete combustion is preferred over incomplete combustion in a domestic boiler.

> Cambridge International IGCSE Chemistry (0620) — 11.3 Fuels · State and Explain · 4 marks

## Mark scheme (4 marks)

1. Complete combustion of methane produces carbon dioxide
2. Complete combustion of methane produces water
3. Incomplete combustion produces carbon monoxide, which is toxic / poisonous to humans
4. Complete combustion releases more energy than incomplete combustion / complete combustion is more efficient

## 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 "State and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/methane-is-the-main-hydrocarbon-in-6d2a2d0b) · Published by Druglandscape Ltd.