# Catalytic cracking and steam cracking are two processes used to break down long-chain hydrocarbons. Describe both processes and explain why cracking is important to the petrochemical industry.

> AQA A-Level Chemistry (7405) — 3.3.14 Organic synthesis (A-Level only) · Describe · 5 marks

## Mark scheme (5 marks)

1. Catalytic cracking: long-chain hydrocarbons are heated to vaporise them / turned into a gas
2. Catalytic cracking: the vapour is passed over a hot powdered aluminium oxide catalyst
3. Steam cracking: the hydrocarbon vapour is mixed with steam and heated to a very high temperature
4. Cracking produces smaller, more useful molecules / produces alkenes and shorter-chain alkanes
5. The products are important as fuels or as feedstock / alkenes are used to make polymers or other chemicals

## Key terms

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

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](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/catalytic-cracking-and-steam-cracking-are-c0d5e871) · Published by Druglandscape Ltd.