# Methane, ethane and propane are the first three members of the alkane homologous series. State the molecular formula of propane and explain what is meant by the term 'homologous series', referring to functional groups and chemical properties in your answer.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 4.1 Introduction · State and Explain · 4 marks

## Mark scheme (4 marks)

1. Correct molecular formula of propane: C₃H₈
2. A homologous series is a series of compounds with the same functional group
3. Members of a homologous series have similar chemical properties
4. Each successive member differs by CH₂ (one carbon and two hydrogen atoms)

## Key terms

- [molecular formula](https://www.gradenine.co.uk/glossary/molecular-formula)
- [homologous series](https://www.gradenine.co.uk/glossary/homologous-series)
- [functional group](https://www.gradenine.co.uk/glossary/functional-group)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "State and 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/methane-ethane-and-propane-are-the-4cf2c460) · Published by Druglandscape Ltd.