# Crude oil is a mixture of hydrocarbons, including alkanes. Describe the structure and bonding of alkanes, and explain why alkanes are described as saturated hydrocarbons. In your answer, state one use of alkanes as fuels and explain why alkanes undergo complete combustion in excess oxygen.

> Edexcel A-Level Chemistry (9CH0) — 6.2 Alkanes · Describe · 5 marks

> Alkanes are obtained from crude oil by fractional distillation. They are widely used as fuels in homes, vehicles and power stations.

## Mark scheme (5 marks)

1. Alkanes contain only carbon and hydrogen atoms (are hydrocarbons)
2. Alkanes contain only single (C–C and C–H) covalent bonds
3. Saturated means alkanes contain no carbon–carbon double bonds (C=C)
4. Named use of an alkane as a fuel, e.g. methane used in natural gas for heating/cooking, butane in camping gas, or petrol/diesel (octane) in vehicles
5. In complete combustion, alkanes react with excess oxygen to produce only carbon dioxide and water (releasing energy)

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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/crude-oil-is-a-mixture-of-4b0826be) · Published by Druglandscape Ltd.