IGCSE §5: Solids, Liquids and Gases · IGCSE
Specific Heat Capacity
Revision notes on Specific Heat Capacity for the OCR A-level Physics specification (H556). Free to read, with 5 practice questions in the app.
Specific heat capacity (c) — the energy needed to raise the temperature of 1 kg of a substance by 1 °C (equivalently, by 1 K).
E = m c ΔT
with energy in joules, mass in kilograms, specific heat capacity in J/(kg °C) and temperature change in °C or K. Because a change of 1 °C is the same size as a change of 1 K, either unit works here — but only for a change, never for a temperature itself.
Water has an unusually high specific heat capacity, about 4200 J/(kg °C). That means a great deal of energy is needed to warm it, and it releases a great deal as it cools.
This explains several things at once:
- Water is used in central heating because it carries a lot of energy per kilogram from the boiler to the radiators.
- Coastal climates are milder than inland ones. The sea warms and cools slowly, moderating the temperature of the land nearby.
- A hot water bottle stays warm for hours, releasing its energy gradually.
- Car engines are water-cooled because water absorbs a lot of energy for a modest rise in temperature.
By contrast a metal such as copper, at about 390 J/(kg °C), heats up rapidly for the same energy — which is why a metal saucepan handle becomes too hot to hold while the water inside is still warming.
ΔT is a change, not a temperature. Heating water from 20 °C to 60 °C gives ΔT = 40 °C, not 60. Substituting the final temperature rather than the change is the single most common error here.
Measuring specific heat capacity — take a block of known mass with a hole for an electric heater and one for a thermometer. Supply a measured amount of electrical energy (E = IVt), record the temperature rise, and calculate c = E ÷ (mΔT). Insulating the block reduces energy lost to the surroundings, which otherwise makes the measured value of c come out too high, since some of the supplied energy never reached the block.
Example: heating 0.30 kg of water from 18 °C to 78 °C needs E = mcΔT = 0.30 × 4200 × 60 = 75 600 J. The same energy into 0.30 kg of copper would raise it by 75 600 ÷ (0.30 × 390) = 646 °C — enough to melt most things touching it.
5 questions on Specific Heat Capacity
Reading is not revising. This topic has 5 questions in the app — multiple choice, calculations, and written answers marked against the mark scheme, point by point. Miss one and it comes back later with its options reshuffled, so you have to know it rather than remember where the answer sat.
- Every topic of Edexcel International GCSE Physics (4PH1)
- Flashcards and every equation, linked to the topic it comes from
- Full mock papers in the real paper structure
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