Q = mcθ
When a substance takes in or gives out heat its temperature changes. The heat exchanged can be worked out step by step.
Heat to raise 1 kg by 1 °C = c
Heat to raise m kg by 1 °C = mc
Heat to raise m kg by θ °C = mcθ
Quantity of heat
Q = mcθ
- Q — the quantity of heat (J)
- m — the mass (kg)
- c — the specific heat capacity (J kg-1 K-1 or J kg-1 °C-1)
- θ — the change in temperature (K or °C)
A kelvin and a degree Celsius are the same size, so a temperature change can be taken in either.
Worked example
Heating 6 kg of copper by 20 K (c = 400 J kg-1 K-1)
1 kg by 1 K: 400 J
6 kg by 1 K: 6 × 400 J
6 kg by 20 K: 6 × 400 × 20 J
= 48 000 J