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Grade 10 Advanced About 20 min Version 1 Awaiting review Premium

Specific heat capacity: why water heats up slowly

Different substances need different amounts of energy to warm up. The specific heat capacity (c) of a substance is the energy needed to raise the temperature 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

  1. Heat 1 kg of water with the 100 W heater. Record the temperature after 2, 5 and 10 minutes.
  2. Heat 1 kg of oil, aluminium and sand for 5 minutes each and record.
  3. 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).