LECTURE PHYSICAL CHEMISTRY 3rd EDITION ROBERT G. MORTIMER

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Heat Transferred during Phase Changes
When a phase change occurs, heat can be
transferred to or from the system without changing its
temperature or its pressure. This heat is sometimes
called latent heat.
The amount of latent heat per unit mass is
characteristic of the substance and the phase
transition.
•The latent heat of fusion (melting) is denoted by
∆ fus H. For water at 0 ◦ C and a constant pressure of
1.000 atm ∆ fus H equals 79.72 cal g −1 .
•The latent heat of vaporization (boiling) is denoted
by ∆ vap H. For water at 100 ◦ C and 1.000 atm ∆ vap H
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equals 539.55 cal g −1 .
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