# Crude oil is described as a finite resource. Explain what is meant by the term 'finite resource' and describe the origin of crude oil, including the type of ancient biomass from which it formed.

> AQA A-Level Chemistry (7405) — 3.3.1 Introduction to organic chemistry · Explain · 5 marks

## Mark scheme (5 marks)

1. Finite resource means it cannot be replaced / will eventually run out / is being used up faster than it is formed
2. Crude oil is the remains of ancient biomass / dead organisms
3. The biomass consisted mainly of plankton
4. The plankton / biomass was buried in mud
5. Most of the compounds in crude oil are hydrocarbons / molecules made up of hydrogen and carbon only

## Key terms

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

## 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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/crude-oil-is-described-as-a-071bf8a0) · Published by Druglandscape Ltd.