# Crude oil contains many long-chain hydrocarbons that are in low demand. Explain why the oil industry uses cracking to improve the usefulness of these long-chain hydrocarbons, and describe how catalytic cracking is carried out.

> OCR GCSE Chemistry A: Gateway Science (J248) — C6.1 Improving processes and products · Explain · 4 marks

> Crude oil is a finite resource. When crude oil is fractionally distilled, large quantities of long-chain hydrocarbons are produced. These fractions are less commercially valuable than shorter-chain products such as petrol and plastics feedstocks.

## Mark scheme (4 marks)

1. Long-chain hydrocarbons are in low demand / there is greater demand for shorter-chain hydrocarbons (e.g. petrol / fuels)
2. Cracking breaks down / splits long-chain hydrocarbons into smaller, more useful molecules
3. The long-chain hydrocarbons are heated to vaporise / turn them into a gas
4. The vapour is passed over a hot powdered aluminium oxide catalyst, causing the long-chain molecules to split apart on the surface of the catalyst

## Key terms

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

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/crude-oil-contains-many-long-chain-hydrocarbons-de0b5e45) · Published by Druglandscape Ltd.