Specific heat capacity: why water heats up slowly
Heat water, cooking oil, an aluminium block and dry sand with the same immersion heater and compare how much their temperatures rise.
Core concept
Specific heat capacity is the energy needed to raise 1 kg of a substance by 1 °C; water's is very high
Topic: Heat
Different substances need different amounts of energy: What is needed to make things move, heat up, light up or grow. All key words to warm up. The specific heat capacity (c) of a substance is the energy needed to raise the temperature: How hot or cold something is, measured in degrees Celsius (°C). All key words of 1 kg of it by 1 °C, measured in J/(kg °C). The energy supplied E = m × c × ΔT, so ΔT = E ÷ (m × c). A joulemeter measures the energy an electric heater supplies. Water has a very high specific heat capacity, about 4200 J/(kg °C), so it warms up and cools down slowly.
What you will learn
- Use E = m × c × ΔT to calculate temperature rise or specific heat capacity.
- Compare the specific heat capacities of water, oil, aluminium and sand.
- Explain everyday effects of water's high specific heat capacity.
Before you start
- Know that energy is measured in joules and power in watts (1 W = 1 J/s).
Materials
- Water, cooking oil, an aluminium block and dry sand, 1 kg and 2 kg of each
Equipment
- 100 W immersion heater and a joulemeter
- Thermometer, stopwatch and insulation
Procedure
- Heat 1 kg of water with the 100 W heater. Record the temperature after 2, 5 and 10 minutes.
- Heat 1 kg of oil, aluminium and sand for 5 minutes each and record.
- Heat 2 kg of water for 5 minutes and compare with 1 kg.
How this simulation is simplified
- Every sample starts at 20 °C, is well insulated and loses no heat; the heater gives a steady 100 W.
- Specific heat capacities: water 4200, cooking oil 2000, aluminium 900, dry sand 800 J/(kg °C).