# A large block of ice floats partially submerged in seawater. The density of ice is approximately 917 kg/m³ and the density of seawater is approximately 1025 kg/m³. Explain, using the concept of density, why ice floats in seawater rather than sinking.

> Cambridge International IGCSE Physics (0625) — 1.4 Density · Explain · 4 marks

## Mark scheme (4 marks)

1. Density is defined as mass per unit volume
2. The density of ice (917 kg/m³) is less than the density of seawater (1025 kg/m³)
3. A given volume of ice has less mass than the same volume of seawater
4. Because the ice is less dense than the seawater, the seawater exerts an upward force (upthrust) sufficient to support the ice, so it floats

## Key terms

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

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-large-block-of-ice-floats-e4938824) · Published by Druglandscape Ltd.