During a change of state, such as melting or boiling, heat is absorbed or released without a change in temperature. Specific latent heat is defined as the amount of heat required to change the state of one unit of mass of a substance. The specific latent heat of fusion is the amount of heat required to melt one unit of mass of a solid into a liquid, while the specific latent heat of vaporization is the amount of heat required to vaporize one unit of mass of a liquid into a gas. Latent heat is used in applications like autoclaving hospital equipment and cooking fish quickly using steam.

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2. 2
Specific Latent Heat
Applications
Problem solving
Experiment
Definition
Change of state of matter
Fusion
Vaporisation

3. 3
Learning outcomes
• State that transfer of heat during a change of
phase does not cause a change in temperature
• Define specific latent heat
• State that l = Q/m
• Determine the specific latent heat of a fusion.
• Determine the specific latent heat of vaporization
• Solve problems involving specific latent heat

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Change of phase (state) of matter
Melting Boiling
Freezing Condensation
Heat absorbed
Heat released (liberated)
at constant
temperature during a

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Amount of heat required to
convert unit mass of a solid into
liquid without a change in
temperature

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Amount of heat required to
convert unit mass of a liquid into
vapour without a change in
temperature

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Latent heat of
vaporisation is
used in an
autoclave to
sterilise
hospital
equipment
Steam releases
large quantity of
latent heat when
changes to water
during
condensation.
This large
amount of
heat cooks the
fish in a very
short time

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Pg 121 : Mastery practice 4.3