When a substance is heated, energy is stored in its thermal store and its temperature rises. The change in thermal energy is ΔE = m × c × Δθ, where m is mass in kg, c is the specific heat capacity in J/kg °C and Δθ is the temperature change in °C. The specific heat capacity of a substance is the amount of energy needed to raise the temperature of one kilogram of the substance by one degree Celsius.
For example, warming 2 kg of water (c = 4200 J/kg °C) by 10 °C needs 2 × 4200 × 10 = 84000 J. A substance with a high specific heat capacity needs more energy to warm up than one with a low specific heat capacity.
Required practical: to find the specific heat capacity of a metal block, measure its mass, then put an electric heater and a thermometer in holes in the block. Record the starting temperature, switch on the heater for a set time and record the final temperature. The energy supplied is the electrical work done by the heater. Wrap the block in insulation to reduce thermal energy lost to the surroundings. Then rearrange the equation to find c.
A 0.5 kg block of aluminium (c = 900 J/kg °C) warming by 20 °C gains 0.5 × 900 × 20 = 9000 J, so its thermal energy store increases.