# Chlorofluorocarbons (CFCs) were once widely used in aerosol sprays and refrigerators. Scientists discovered that CFCs cause damage to the ozone layer. Explain why the ozone layer is important and describe how CFCs cause damage to it.

> OCR A-Level Chemistry B: Salters (H433) — OZ The ozone story · Explain · 5 marks

> The ozone layer sits in the stratosphere, approximately 15–35 km above the Earth's surface. International agreements such as the Montreal Protocol have restricted the use of CFCs since the late 1980s.

## Mark scheme (5 marks)

1. The ozone layer absorbs (harmful) ultraviolet (UV) radiation from the Sun
2. Without the ozone layer, increased UV radiation reaching Earth's surface would cause harm to living organisms / increased skin cancer / damage to ecosystems
3. CFCs are broken down / decomposed by UV radiation (in the stratosphere), releasing chlorine (free radicals / atoms)
4. Chlorine (free radicals / atoms) react with ozone molecules, breaking them down / converting ozone (O₃) into oxygen (O₂)
5. Chlorine acts as a catalyst / is regenerated / one chlorine atom can destroy many ozone molecules, so a small amount of CFC causes large-scale damage

## Key terms

- [ozone layer](https://www.gradenine.co.uk/glossary/ozone-layer)

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](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/chlorofluorocarbons-cfcs-were-once-widely-used-c9fd55b1) · Published by Druglandscape Ltd.