# Propene and propane are both hydrocarbons with three carbon atoms. Describe how the structures of propene and propane differ, and explain how this structural difference affects their reactions with bromine water.

> Edexcel GCSE Chemistry (1CH0) — 10.2 Alkenes (Chem only) · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. Propene contains a carbon–carbon double bond (C=C) whereas propane only contains carbon–carbon single bonds
2. Propene decolourises / decolourisez bromine water (orange to colourless)
3. Propane does not decolourise bromine water / bromine water remains orange with propane
4. The C=C double bond in propene allows addition reactions to occur, so bromine adds across the double bond; propane cannot undergo addition reactions as it has no double bond

## Key terms

- [bromine water](https://www.gradenine.co.uk/glossary/bromine-water)

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/propene-and-propane-are-both-hydrocarbons-ef761d97) · Published by Druglandscape Ltd.