# Crude oil contains hydrocarbons of different chain lengths. During fractional distillation, short-chain alkanes and long-chain alkanes are separated into different fractions. Compare the properties of short-chain alkanes with those of long-chain alkanes, and explain why short-chain fractions are more useful as fuels.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 4.3 Alkanes · Compare · 4 marks

## Mark scheme (4 marks)

1. Short-chain alkanes have lower boiling points than long-chain alkanes
2. Short-chain alkanes are more volatile / evaporate more easily than long-chain alkanes
3. Short-chain alkanes flow more easily / are less viscous than long-chain alkanes
4. Short-chain alkanes ignite more easily / are more flammable, making them more useful as fuels because they release energy when burned

## Key terms

- [alkanes](https://www.gradenine.co.uk/glossary/alkanes)
- [fractional distillation](https://www.gradenine.co.uk/glossary/fractional-distillation)
- [fractions](https://www.gradenine.co.uk/glossary/fractions)
- [crude oil](https://www.gradenine.co.uk/glossary/crude-oil)
- [hydrocarbons](https://www.gradenine.co.uk/glossary/hydrocarbons)
- [fuel](https://www.gradenine.co.uk/glossary/fuel)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Compare" 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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