# Ethane (C₂H₆) and ethene (C₂H₄) are both hydrocarbons. Ethene is described as an unsaturated hydrocarbon, while ethane is described as a saturated hydrocarbon. Explain the difference between a saturated and an unsaturated hydrocarbon, and describe a chemical test that would allow you to distinguish between ethane and ethene, including the result for each compound.

> WJEC GCSE Chemistry (Wales) — 2.6 Carbon chemistry / organic chemistry · Explain · 4 marks

> Ethane and ethene are both colourless gases at room temperature and are members of different homologous series.

## Mark scheme (4 marks)

1. A saturated hydrocarbon contains only single carbon–carbon bonds (C–C).
2. An unsaturated hydrocarbon contains at least one carbon–carbon double bond (C=C).
3. Add bromine water to each compound — the bromine water decolourises / turns from orange-brown to colourless with ethene.
4. The bromine water remains orange-brown / does not decolourise with ethane.

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Chemistry (Wales)](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/ethane-c-h-and-ethene-c-h-are-d707075e) · Published by Druglandscape Ltd.