# Alkanes are a homologous series of hydrocarbons. Explain what is meant by the term 'homologous series' and describe the general trend in the physical properties of alkanes as the number of carbon atoms in the chain increases. Include in your answer a description of the complete combustion of methane.

> Edexcel A-Level Chemistry (9CH0) — 6.2 Alkanes · Explain · 5 marks

> Methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀) are the first four members of the alkane homologous series.

## Mark scheme (5 marks)

1. A homologous series is a series of compounds that share the same general formula / differ by CH₂ between successive members
2. Alkanes have the general formula CₙH₂ₙ₊₂
3. Boiling point / melting point increases as the number of carbon atoms increases
4. Complete combustion of methane produces carbon dioxide and water
5. Complete combustion requires excess / sufficient oxygen (or occurs in a plentiful supply of oxygen)

## Key terms

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

## 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)
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Source: [GradeNine](https://www.gradenine.co.uk/q/alkanes-are-a-homologous-series-of-ecde7418) · Published by Druglandscape Ltd.