Science glossary film: Density

Mass per unit of volume. The density of all substances varies with temperature and pressure: as a rule increasing the temperature reduces the density, as does reducing the pressure. Water is unusual: it is most dense at 4°C, and becomes less dense whether temperature increases or decreases from that point.

The density of all substances varies with temperature and pressure: as a rule increasing the temperature reduces the density, as does reducing the pressure. Water is unusual: it is most dense at 4°C, and becomes less dense whether temperature increases or decreases from that point.