# Explain why metals have high thermal conductivity and why this property decreases when the metal forms an alloy.

> IB DP Chemistry Standard Level (2023 syllabus) — S2.3 The metallic model · Explain · 4 marks

## Mark scheme (4 marks)

1. In a metal, delocalised (free/mobile) electrons are present throughout the lattice.
2. These delocalised electrons can gain kinetic energy from a heat source and transfer it rapidly through the lattice, giving high thermal conductivity.
3. In an alloy, atoms of different sizes are introduced, distorting the regular lattice structure.
4. This distortion increases scattering/collision of delocalised electrons, impeding their movement and reducing thermal conductivity.

## Key terms

- [thermal conductivity](https://www.gradenine.co.uk/glossary/thermal-conductivity)
- [alloy](https://www.gradenine.co.uk/glossary/alloy)

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](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/explain-why-metals-have-high-thermal-0a6d8f15) · Published by Druglandscape Ltd.