# Sodium chloride is an ionic compound used to preserve food. Explain why sodium chloride has a high melting point but does not conduct electricity when solid, yet does conduct electricity when melted.

> OCR A-Level Chemistry A (H432) — 2.4 Electrons, bonding and structure · Explain · 5 marks

> Sodium chloride is made up of sodium ions (Na⁺) and chloride ions (Cl⁻) arranged in a giant lattice structure. It is widely used in the food industry as a preservative.

## Mark scheme (5 marks)

1. Sodium chloride is held together by strong electrostatic forces (between oppositely charged ions)
2. A large amount of energy is needed to overcome these strong electrostatic forces, so the melting point is high
3. In the solid state, the ions are held in fixed positions and cannot move
4. Therefore charge cannot be carried and electricity cannot be conducted when solid
5. When melted, the ions are free to move and carry charge, so the ionic compound conducts electricity

## Key terms

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

## 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)
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Source: [GradeNine](https://www.gradenine.co.uk/q/sodium-chloride-is-an-ionic-compound-35ebb25e) · Published by Druglandscape Ltd.