# Cracking is an important industrial process used in the oil refinery industry. Explain why cracking is carried out and describe what happens during the cracking of a long-chain alkane molecule.

> Edexcel A-Level Chemistry (9CH0) — Topic 5 Organic chemistry II · Explain and Describe · 5 marks

> Long-chain hydrocarbons produced from fractional distillation of crude oil are less useful than shorter-chain hydrocarbons. Cracking converts these long-chain molecules into more useful, shorter-chain products.

## Mark scheme (5 marks)

1. There is greater demand / more uses for shorter-chain hydrocarbons (e.g. as fuels) than for longer-chain ones
2. Cracking involves breaking (thermal decomposition of) long-chain hydrocarbon molecules into shorter molecules
3. High temperature is required / the process is carried out at high temperature
4. A catalyst is used (e.g. aluminium oxide / silica / zeolite) OR the process can be carried out without a catalyst using very high temperatures (steam cracking)
5. Products include a shorter-chain alkane AND an alkene (unsaturated molecule / molecule with a C=C double bond)

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain and Describe" 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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Source: [GradeNine](https://www.gradenine.co.uk/q/cracking-is-an-important-industrial-process-dc7cda6f) · Published by Druglandscape Ltd.