Page 27 - FINAL DBS10012_HEAT TEMPERATURE 20102022 (2) (1)
P. 27
1.5 SPECIFIC LATENT HEAT
The amount of heat required to change the phase of substance depends on the mass and the type of
material of the substance. A small ice cube melts quickly but a large block of ice melts very slowly. A
piece of wax at its melting point melts very quickly but a piece of iron of the same mass melts slowly.
The specific heat latent of a substance is the amount of heat required to change the phase of 1 kg of
the substance at a constant temperature.
Specific heat latent, ;
=
Where, Q = latent heat absorbed or released by the substance,
m = mass of the substance , with unit in J/kg
The latent heat absorbed or released when a substance of mass m changes from one phase to
another is given by:
=
The specific latent heat (SLH) of fusion of a substance is defined as the amount of heat required to
change 1 kg of the substance from a solid to liquid phase without a change in temperature. The
specific latent heat (SLH) of vaporization of a substance is defined as the amount of heat required
to change 1 kg of the substance from liquid to gaseous phase without a change in temperature. Table
6.4 shows the specific latent heats of some common substance.
21
