# Methane, ethane, propane and butane are all members of the alkane homologous series. Describe four properties that all members of a homologous series share, and explain why alkanes are described as saturated hydrocarbons.

> AQA A-Level Chemistry (7405) — 3.3.1 Introduction to organic chemistry · Describe · 5 marks

## Mark scheme (5 marks)

1. Members of a homologous series have the same functional group / same general formula (CnH2n+2 for alkanes)
2. Members of a homologous series have similar chemical properties
3. Members of a homologous series differ by one CH2 unit / show a gradual trend in physical properties
4. Alkanes are saturated because they contain only single bonds between carbon atoms / no carbon–carbon double bonds
5. Alkanes are hydrocarbons because they contain hydrogen and carbon atoms only

## Key terms

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

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/methane-ethane-propane-and-butane-are-c098df77) · Published by Druglandscape Ltd.