This is a metal tank (210 x 80 x 75mm) with 5 inlets to accommodate 3mm rods of copper, iron, brass, aluminium and glass, which are mounted in rubber stoppers. Once the rods are coated in paraffin wax, the thermal properties of each rod can be compared. The coefficient of thermal conductivity is a measure of the steady-state rate at which a rod of a given material conducts thermal energy when the two ends of the rod are held at different temperatures. The rate at which a temperature pulse travels down the rod depends on the thermal conductivity, and the reciprocals of the density and the specific heat capacity; this combination is called the diffusivity.