# Butene is an alkene with the molecular formula C₄H₈. Explain why butene belongs to the alkenes homologous series and describe how a student could use a chemical test to distinguish butene from butane.

> AQA A-Level Chemistry (7405) — 3.3.4 Alkenes · Explain and Describe · 5 marks

> Butene and butane are both hydrocarbons that can be produced from crude oil. They have similar molecular formulae but different chemical properties.

## Mark scheme (5 marks)

1. Butene contains a carbon-carbon double bond / is unsaturated
2. Butene fits the general formula CₙH₂ₙ (e.g. C₄H₈ fits with n=4)
3. Alkenes have the same functional group / similar chemical properties to other members of the series
4. Add bromine water to each sample / shake each hydrocarbon with bromine water
5. Bromine water turns from orange to colourless with butene but remains orange with butane

## Key terms

- [alkenes](https://www.gradenine.co.uk/glossary/alkenes)
- [homologous series](https://www.gradenine.co.uk/glossary/homologous-series)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain and 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/butene-is-an-alkene-with-the-19a5915f) · Published by Druglandscape Ltd.