# Methane, propane and octane are all alkanes. Explain why alkanes are described as saturated hydrocarbons and explain why shorter-chain alkanes, such as methane, are more useful as fuels than longer-chain alkanes, such as octane.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 4.3 Alkanes · Explain · 4 marks

## Mark scheme (4 marks)

1. Alkanes contain only carbon and hydrogen atoms, so they are hydrocarbons
2. Alkanes contain only single bonds between carbon atoms, so they are saturated
3. Shorter-chain alkanes have lower boiling points / are more volatile, so they are easier to ignite / burn more readily
4. Shorter-chain alkanes flow / pour more easily (lower viscosity) making them easier to transport and use as fuels

## Key terms

- [saturated](https://www.gradenine.co.uk/glossary/saturated)
- [hydrocarbon](https://www.gradenine.co.uk/glossary/hydrocarbon)
- [alkane](https://www.gradenine.co.uk/glossary/alkane)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/methane-propane-and-octane-are-all-28cded40) · Published by Druglandscape Ltd.