# Cracking is used in the petrochemical industry to break down larger hydrocarbon molecules. Explain why cracking is necessary and describe what happens during catalytic cracking.

> AQA A-Level Chemistry (7405) — 3.3.1 Introduction to organic chemistry · Explain · 5 marks

## Mark scheme (5 marks)

1. There is greater demand for shorter-chain hydrocarbons (fractions) than for longer-chain hydrocarbons
2. Cracking converts long-chain hydrocarbons into smaller, more useful molecules
3. The long-chain hydrocarbon is heated to vaporise it (turned into a gas)
4. The vapour is passed over a hot powdered aluminium oxide catalyst
5. The products of cracking include alkanes and alkenes

## Key terms

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

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/cracking-is-used-in-the-petrochemical-eb5bcbd9) · Published by Druglandscape Ltd.