# Explain why cracking is carried out in the petrochemical industry and describe the two methods used to crack hydrocarbons.

> AQA A-Level Chemistry (7405) — 3.3.10 Aromatic chemistry (A-Level only) · Explain · 5 marks

## Mark scheme (5 marks)

1. There is greater demand for shorter-chain hydrocarbons / fractions than for longer-chain ones
2. Cracking breaks down larger / longer-chain hydrocarbons into smaller / shorter-chain molecules
3. Catalytic cracking: the hydrocarbon vapour is passed over a hot powdered aluminium oxide catalyst
4. Steam cracking: the hydrocarbon vapour is mixed with steam and heated to a very high temperature
5. Products of cracking include alkenes (as well as alkanes), which can be used to make polymers / as fuels

## Key terms

- [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 "Explain" 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/explain-why-cracking-is-carried-out-8c952787) · Published by Druglandscape Ltd.