# Alkanes are used as fuels. Describe what happens when a long-chain alkane undergoes cracking, and explain why cracking is carried out in the petroleum industry.

> Cambridge International IGCSE Chemistry (0620) — 11.4 Alkanes · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. A long-chain alkane is broken down / split into smaller molecules
2. Produces a shorter-chain alkane AND an alkene (unsaturated product)
3. Cracking is carried out because there is greater demand for shorter-chain / smaller fractions (e.g. petrol / gasoline) than for longer-chain fractions
4. Alkenes produced by cracking are used as monomers / to make plastics / polymers, making cracking industrially valuable

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-used-as-fuels-describe-8b52c0e1) · Published by Druglandscape Ltd.