Heating and specific heat capacity

Heating a material

Heating increases a material’s thermal store. Different materials need different amounts of energy for the same temperature rise.

Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C.

An ideal heating model: all supplied energy enters the block. Real experiments lose some energy to the surroundings.

Use the temperature change

Δθ = final temperature − initial temperature. Use the rise, not the final temperature.

Example: 2 kg, c = 500 J/(kg °C), warming from 20 °C to 30 °C:

Required practical: find c

1. Measure the mass of a metal block with a balance.
2. Insert an electric heater and thermometer into its holes. Insulate the block and record its initial temperature.
3. Connect the heater to a suitable power supply and joulemeter. Switch on and record the energy supplied and temperature rise.
4. Calculate c = E / (mΔθ). Repeat readings to check the result.

A known heater power and time can give E = Pt instead of a joulemeter. Good contact between thermometer and block improves the temperature reading.

Follow your teacher’s instructions: the heater and block can become hot.

Explain the main error

Some supplied energy heats the surroundings rather than the block. Using all the electrical input as the block’s energy gain therefore tends to overestimate c.

Insulation reduces this unwanted transfer. Record temperature carefully and allow the thermometer to respond.