# Ethene is produced by cracking long-chain hydrocarbons. Describe what happens during steam cracking and explain why cracking is an important industrial process.

> AQA A-Level Chemistry (7405) — 3.3.16 Chromatography (A-Level only) · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. Long-chain hydrocarbons are heated to vaporise them / turn them into a gas
2. The hydrocarbon vapour is mixed with steam and heated to a very high temperature
3. Thermal decomposition causes the long-chain molecules to split into smaller molecules
4. Cracking produces alkenes (such as ethene), which are used to make polymers / other chemicals
5. Cracking converts less useful long-chain hydrocarbons into shorter-chain molecules that are in greater demand / more useful as fuels because they are more flammable

## Key terms

- [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 and Explain" 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/ethene-is-produced-by-cracking-long-chain-7ac35c90) · Published by Druglandscape Ltd.