# Ethanol can be manufactured by the fermentation of sugar solutions using yeast. Describe what happens during fermentation and explain why ethanol produced this way is considered a more sustainable fuel than petrol.

> AQA GCSE Chemistry (8462) — 4.7.2 Reactions of alkenes and alcohols (Chem only) · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. Fermentation is a chemical process in which glucose/sugar is broken down anaerobically (without oxygen) by yeast
2. Fermentation produces ethanol (and carbon dioxide)
3. Ethanol is produced from a renewable/biological source (sugar/plants) whereas petrol is derived from crude oil, which is a finite/non-renewable resource
4. The carbon dioxide released when ethanol burns was previously absorbed by the plants during photosynthesis, so it is (approximately) carbon neutral / does not add new carbon dioxide to the atmosphere

## Key terms

- [fermentation](https://www.gradenine.co.uk/glossary/fermentation)
- [ethanol](https://www.gradenine.co.uk/glossary/ethanol)

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/ethanol-can-be-manufactured-by-the-a9b60797) · Published by Druglandscape Ltd.