86 Chapter 4 • Heat Summary 4.3


Specific heat capacity (c in J/kg °C) Definition of specific heat capacity Specific heat capacity is the amount of heat energy required to raise the temperature of 1 kg of a substance 1 °C (or 1 K).


• Q =mc3t joules where Q = heat energy 3t = change in temperature (t2 – t1) – remember to convert kJ/kg °C to “J”/kg °C (× 1 000).


Heat transfer – calculations


• Heat lost = heat gained mc3t = mc3t


Thermal expansion • Volumetric expansion – Ball and ring (experiment 4.3, page 76). • Linear expansion (increase in length with increase in temperature). • Bimetal strip (experiment 4.4, page 77) – uses; thermostat switches, overload devices and fire detectors.


• Shrinking ring gears onto flywheels. • Unwanted effects – examples are expansion gaps in; rings on pistons (motor cars), railway lines, bridges and concrete drive-ways.


• 3ℓ = αℓo3t • ℓf = ℓo ± 3ℓ


Definition of coefficient of linear expansion (α) Te coefficient of linear expansion is the increase in length per unit length of a material per degree rise in temperature.


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