# Propene (C₃H₆) is an alkene produced during the cracking of long-chain hydrocarbons. Explain why propene is described as unsaturated and outline how bromine water can be used to distinguish propene from propane.

> Edexcel A-Level Chemistry (9CH0) — Topic 3 Organic chemistry I · Explain · 5 marks

> Propene (C₃H₆) is a short-chain alkene obtained from the cracking of larger hydrocarbon molecules found in crude oil. It is an important feedstock for the chemical industry.

## Mark scheme (5 marks)

1. Propene is unsaturated because it contains a carbon-to-carbon double bond (C=C)
2. Propene does not contain the maximum possible number of hydrogen atoms (it is not saturated / not fully hydrogenated)
3. Add bromine water to each compound
4. Propene decolourises (turns from orange/brown to colourless) the bromine water
5. Propane does not decolourise the bromine water (it remains orange/brown) because propane is saturated and does not undergo addition reactions

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "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/propene-c-h-is-an-alkene-produced-d20a5e67) · Published by Druglandscape Ltd.