Specific Heat Capacity
Q = mcΔT links heat energy, mass, material, and temperature change.
Specific heat capacity (c):
The energy required to raise the temperature of 1 kg of a substance by 1°C (or 1 K). Q = mcΔT
- Q = heat energy (J), m = mass (kg), c = specific heat capacity (J/kg°C), ΔT = temperature change (°C or K)
Typical values:
| Material | c (J/kg°C) |
|---|---|
| Water | 4200 |
| Aluminium | 900 |
| Iron | 450 |
| Copper | 400 |
Why water has high c:
- Water has strong hydrogen bonds that require much energy to break before temperature rises
- High c makes water excellent for cooling systems and climate regulation
Example: How much energy is needed to heat 2 kg of water from 20°C to 100°C?
Q = 2 × 4200 × 80 = 672 000 J = 672 kJ
Experimental measurement:
- Use electrical heater (power P, time t): energy = Pt
- Measure temperature change with thermometer
- c = Q/(mΔT) = Pt/(mΔT)
- Q = mcΔT. c = specific heat capacity (J/kg°C).
- Water: c = 4200 J/kg°C (highest of common substances).
- Electrical heater: energy = power × time = Pt.