# Explain why tungsten is used to make the filaments in incandescent light bulbs and why lead is used as a radiation shield in X-ray rooms. Give two reasons in total, one for each use.

> Cambridge International IGCSE Chemistry (0620) — 9.2 Uses of metals · Explain · 4 marks

## Mark scheme (4 marks)

1. Tungsten has a very high melting point, so it does not melt when the filament becomes extremely hot
2. Tungsten has a high electrical resistance, allowing it to heat up and emit light when current flows through it
3. Lead has a very high density, so it absorbs / stops X-rays (or other ionising radiation) from passing through
4. Lead does not react with / is not corroded by the surroundings, so it remains effective as a shield over a long period of time

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