# Carbon dioxide is a simple molecular compound. Explain why carbon dioxide is described as a compound rather than a mixture, and why it has a low melting point compared to diamond, which is also made up of non-metal atoms.

> OCR A-Level Chemistry A (H432) — 2.1 Atoms, compounds, molecules and equations · Explain · 5 marks

> Carbon dioxide, CO₂, is produced during the combustion of fossil fuels. Diamond is a naturally occurring form of carbon. Both substances contain only non-metal atoms, yet their physical properties are very different.

## Mark scheme (5 marks)

1. A compound contains atoms of different elements chemically bonded together (whereas a mixture does not involve chemical bonding)
2. Carbon dioxide has covalent bonds between the carbon and oxygen atoms
3. Carbon dioxide is a simple molecular substance with intermolecular forces between molecules
4. Only a small amount of energy is needed to overcome these intermolecular forces, giving carbon dioxide a low melting point
5. Diamond is a giant covalent structure with many strong covalent bonds throughout, requiring a large amount of energy to break them, giving diamond a high melting point

## Key terms

- [compound](https://www.gradenine.co.uk/glossary/compound)
- [mixture](https://www.gradenine.co.uk/glossary/mixture)

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](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/carbon-dioxide-is-a-simple-molecular-8e9ef6d0) · Published by Druglandscape Ltd.