# Silicon dioxide (SiO₂) is used to make glass and has a very high melting point. Explain why silicon dioxide has a very high melting point in terms of its giant covalent structure and the bonds present.

> OCR A-Level Chemistry B: Salters (H433) — 2.4 Electrons, bonding and structure · Explain · 5 marks

> Silicon dioxide is a giant covalent structure used in many industrial applications, including the manufacture of glass and ceramics, because of its exceptional thermal stability.

## Mark scheme (5 marks)

1. Silicon dioxide is a giant covalent structure containing many atoms covalently bonded together
2. A covalent bond is a shared pair of electrons between atoms
3. There are very many / a large number of covalent bonds throughout the structure
4. These covalent bonds are strong
5. A large amount of energy is needed to break these bonds, so the melting point is very high

## Key terms

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

## 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)
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