# Describe the process of catalytic cracking and explain why cracking is carried out in industry. In your answer, refer to the products formed.

> AQA A-Level Chemistry (7405) — 3.3.7 Optical isomerism (A-Level only) · Describe · 5 marks

## Mark scheme (5 marks)

1. Long-chain hydrocarbons are heated to vaporise them / turned into a gas
2. The vapour is passed over a hot powdered aluminium oxide catalyst
3. The long-chain molecules break apart / split into smaller molecules
4. Products include smaller alkanes (which are more useful as fuels / more flammable)
5. Alkenes are also produced, which are used to make polymers / other chemicals (OR: demand for shorter-chain fractions is greater than for longer-chain fractions so cracking converts surplus long-chain hydrocarbons into more useful products)

## Key terms

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

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-process-of-catalytic-cracking-cb7e6c03) · Published by Druglandscape Ltd.