# Graphite and diamond are both giant covalent structures made entirely of carbon atoms, yet they have very different physical properties. Explain why graphite is soft and can be used as a lubricant, whereas diamond is the hardest natural substance.

> Cambridge International IGCSE Chemistry (0620) — 2.6 Giant covalent structures · Explain · 4 marks

## Mark scheme (4 marks)

1. In graphite, carbon atoms are arranged in layers (of hexagonal rings)
2. The layers in graphite are held together by weak (intermolecular/van der Waals) forces, allowing them to slide over one another easily
3. In diamond, each carbon atom is covalently bonded to four other carbon atoms (tetrahedral arrangement)
4. Diamond has a rigid three-dimensional network of strong covalent bonds throughout the structure, making it very hard

## Key terms

- [giant covalent structure](https://www.gradenine.co.uk/glossary/giant-covalent-structure)
- [lubricant](https://www.gradenine.co.uk/glossary/lubricant)

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Source: [GradeNine](https://www.gradenine.co.uk/q/graphite-and-diamond-are-both-giant-8446840a) · Published by Druglandscape Ltd.