Internal Energy and Specific Heat Capacity — AQA GCSE Physics
Heating a substance raises its temperature by an amount that depends on its specific heat capacity.
Internal energy
The internal energy of a substance is the total kinetic and potential energy of its particles. Heating a substance increases this internal energy, which can raise its temperature or change its state.
Specific heat capacity
The specific heat capacity of a substance is the energy needed to raise the temperature of 1 kg of the substance by 1 °C.
$$\Delta E = m \times c \times \Delta\theta$$
- ΔE = energy transferred (J)
- m = mass (kg)
- c = specific heat capacity (J/kg°C)
- Δθ = temperature change (°C)
A substance with a high specific heat capacity (like water) needs a lot of energy to warm up and releases a lot when it cools.
Required practical
To measure specific heat capacity, use an electric heater to warm a known mass of material (e.g. a metal block), measuring the energy supplied and the temperature rise, then calculate c = ΔE ÷ (m × Δθ). Insulation reduces heat loss for a more accurate result.
Worked example
Heating 2 kg of water (c = 4200 J/kg°C) by 10 °C: ΔE = 2 × 4200 × 10 = 84 000 J.
Exam tips
- Define specific heat capacity (energy to raise 1 kg by 1 °C).
- Learn ΔE = mcΔθ and rearrange to find c.
- Water has a high specific heat capacity.
- In the practical, use insulation to reduce heat loss.