Specific heat capacity

The specific heat capacity of a substance is the amount of energy needed to raise the temperature of 1 kg of the substance by 1 °C.
ΔE = m c Δθ, where ΔE is the change in thermal energy (J), m the mass (kg), c the specific heat capacity (J/kg °C) and Δθ the temperature change (°C).
Water has a high specific heat capacity (4200 J/kg °C), so it takes a lot of energy to heat and cools slowly. This makes it good for central heating systems.

Rearranging the equation

Measure the mass of a metal block (such as 1 kg of aluminium) and wrap it in insulation to reduce energy loss.
Put an electric heater and a thermometer into the holes in the block. Record the starting temperature.
Switch on the heater and measure the energy transferred with a joulemeter (or calculate it from E = V I t) and the temperature every minute.
Plot temperature against energy transferred. The gradient = 1 ÷ (m c), so c = 1 ÷ (gradient × m).
The measured value is usually too high, because some energy heats the surroundings instead of the block.

The higher the thermal conductivity of a material, the faster energy is transferred through it by conduction.
The rate of cooling of a building depends on the thickness of its walls and their thermal conductivity: thicker walls with lower thermal conductivity cool more slowly.
Loft insulation, cavity wall insulation, double glazing and draught excluders all reduce energy loss from homes.

Specific heat capacity: The energy needed to raise the temperature of 1 kg of a substance by 1 °C.
Thermal energy: Energy in the thermal store of an object, linked to its temperature.
Temperature change: The final temperature minus the starting temperature.
Joulemeter: A meter that measures the energy transferred by an electric circuit.
Thermal conductivity: How well a material conducts thermal energy.
Insulator: A material with low thermal conductivity that reduces energy transfer.