# Methane, pentane and decane are all alkanes found in crude oil. Describe how the properties of these three alkanes change as the number of carbon atoms increases, and explain why these differences make some fractions more useful as fuels for vehicles than others.

> Edexcel GCSE Chemistry (1CH0) — 10.1 Crude oil, hydrocarbons and alkanes (Chem only) · Describe · 4 marks

> Methane has 1 carbon atom, pentane has 5 carbon atoms and decane has 10 carbon atoms.

## Mark scheme (4 marks)

1. Boiling point increases as the number of carbon atoms increases
2. Viscosity increases (or the alkanes become less easy to flow / thicker / less runny) as the number of carbon atoms increases
3. Flammability decreases (or they are harder to ignite / less flammable) as the number of carbon atoms increases
4. Shorter-chain alkanes (e.g. petrol fraction) are more useful as vehicle fuels because they are more flammable / ignite more easily and flow more easily through engines

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](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-pentane-and-decane-are-all-3a491fd0) · Published by Druglandscape Ltd.