# Crude oil is described as a finite resource and a mixture. Explain what is meant by both of these terms and describe how crude oil was formed.

> AQA A-Level Chemistry (7405) — 3.3.2 Alkanes · Explain · 5 marks

## Mark scheme (5 marks)

1. Finite resource means it cannot be replaced / will run out / is non-renewable
2. A mixture contains two or more substances that are not chemically combined
3. Each substance in the mixture retains its own chemical properties
4. Crude oil is the remains of an ancient biomass / mainly plankton
5. The biomass / plankton was buried in mud over millions of years

## Key terms

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

## 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/crude-oil-is-described-as-a-1016e54a) · Published by Druglandscape Ltd.