**Glossary**

**Specific heat capacity (J kg ^{−1} K^{−1})**

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.

**Young's modulus**

A measure of the stiffness of a substance. It provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.

**Shear modulus**

A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain.

**Bulk modulus**

A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume.

**Vapour pressure**

A measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.