Heat of Transformation Question

[MathewsMD]

Given a substance, for example water, does the heat of vapourization vary with pressure or any other variables?

Also, at a specific pressure, water (like all other substances, but at its own respective pressure) changes phases from solid to gas without any intermediate phase. Would the heat of vapourization be the same here as in any other case? (The second question is essentially an extension of the first.)

 

[Chestermiller]

Given a substance, for example water, does the heat of vapourization vary with pressure or any other variables?

The equilibrium vapor pressure is a unique function of temperature, as is the heat of vaporization.

Also, at a specific pressure, water (like all other substances, but at its own respective pressure) changes phases from solid to gas without any intermediate phase. Would the heat of vapourization be the same here as in any other case? (The second question is essentially an extension of the first.)

When ice evaporates, the equilibrium vapor pressure is a function of temperature, as is the heat of vaporization.

The Clapeyron equation describes how the vapor pressure, the temperature, the heat of vaporization, and the specific volumes of the two phases in equilibrium are related.