CHE 104 Lecture 14: Lecture Notes 14

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6 Feb 2017
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February 6rd, 2017
Dr. Townsend
Lecture #14
Energy Changes
Relationships
When a solid melts to a liquid
ΔfusH
When a liquid freezes into a solid
ΔcrystH
When a liquid boils into a gas
ΔvapH
When a gas condenses into a liquid
ΔcondH
When a solid goes through sublimation and turns into a gas
ΔsubH
When a gas goes through deposition and turns into a solid
ΔdepH
When it comes to solid to liquid and liquid to solid, they are the opposite
processes
Their numerical value will be the same
BUT they will have opposite signs (+ or -)
Example:
ΔcrystH = - ΔfusH
ΔcondH = - ΔvapH
ΔdepH = - ΔsubH
Phase Diagrams
Notice in the figure 12.23 that there are three separate phases (solid,
liquid, and gas)
Triple Point: the one combination of pressure and temperature where
solid, liquid, and gas are all present at equilibrium
Liquid is turning into solid, solid is turning into a gas, gas is turning
into a liquid, liquid is turning into a gas… (and so on) all at the
same time!
Critical Point: the point where the liquid/vapor line ends
Recall critical temperature and critical pressure from our
discussions in chapter 11
No matter how much pressure is applied, gas can NOT get to liquid
state
Melting Point/Boiling Point
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