# Ethene is produced when long-chain hydrocarbons from crude oil are cracked. Explain why cracking is carried out in industry and describe the conditions needed for steam cracking.

> AQA A-Level Chemistry (7405) — 3.3.15 NMR spectroscopy (A-Level only) · Explain and Describe · 5 marks

## Mark scheme (5 marks)

1. There is greater demand for shorter-chain hydrocarbons (e.g. as fuels) than for longer-chain hydrocarbons
2. Cracking produces smaller, more useful molecules / fuels from less useful longer-chain hydrocarbons
3. Cracking also produces alkenes, which can be used to make polymers / other chemicals
4. For steam cracking, the long-chain hydrocarbon is heated (vaporised) and mixed with steam
5. The mixture is heated to a very high temperature (causing thermal decomposition)

## Key terms

- [cracking](https://www.gradenine.co.uk/glossary/cracking)
- [steam cracking](https://www.gradenine.co.uk/glossary/steam-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 and Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/ethene-is-produced-when-long-chain-hydrocarbons-e6bcd7e7) · Published by Druglandscape Ltd.