# Methane, ethane, propane and butane are all members of the alkane homologous series. Explain why these four substances belong to the same homologous series and describe how their physical properties change as the number of carbon atoms increases.

> Eduqas A-Level Chemistry — 2.4 Organic compounds · Explain · 5 marks

## Mark scheme (5 marks)

1. All alkanes have the same general formula (CnH2n+2)
2. Each member differs from the next by one CH2 unit (successive members differ by CH2)
3. All alkanes have similar chemical properties (react in the same way / undergo the same reactions)
4. Boiling point increases as the number of carbon atoms increases
5. Viscosity increases (substances become thicker / less runny) as the number of carbon atoms increases

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Chemistry](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/methane-ethane-propane-and-butane-are-6ee67cc1) · Published by Druglandscape Ltd.