# Describe how crude oil forms and explain why it is described as a finite resource.

> OCR GCSE Chemistry A: Gateway Science (J248) — C6.3 Interpreting and interacting with Earth systems · Describe · 4 marks

> Crude oil is one of the most widely used resources on Earth, providing fuels and raw materials for the chemical industry. However, concerns have been raised about its long-term availability.

## Mark scheme (4 marks)

1. Crude oil is formed from the remains of ancient biomass / organisms, consisting mainly of plankton
2. The organisms were buried in mud (over millions of years) / subjected to heat and pressure over time
3. A finite resource is one that cannot be replaced / is being used up faster than it can be reformed
4. Crude oil takes millions of years to form, so once used up it cannot be replenished in a human timescale

## Key terms

- [crude oil](https://www.gradenine.co.uk/glossary/crude-oil)
- [finite resource](https://www.gradenine.co.uk/glossary/finite-resource)

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-crude-oil-forms-and-8cbd18f5) · Published by Druglandscape Ltd.