Thermodynamics and Statistical Mechanics

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Thermodynamics and Statistical Mechanics

• Does the Internal Energy of a Real Gas Depend
  Only on Temperature?

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Change of Phase

• First Law is du dq Pdv
• For a finite change at constant temperature
• Du q PDv
• At transition, u2 u1 l12 P(v2 v1)
• l12 (u2 Pv2) (u1 P v1)
• l12 h2 h1

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Enthalpy and Latent Heat
Enthalpy is defined as h u Pv
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Enthalpy is a State Function
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Does u depend on Volume?
If u u(T, v), then,
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From Cyclical Relation
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Gay-LussacJoule Experiment
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Gay-LussacJoule Results
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Joule-Thompson Throttling Process
A gas passes through a constriction from a region
where it is at high pressure to a region where it
is at lower pressure. The gas expands, and the
temperature of the gas can be lowered. This is an
important tool in low temperature physics.
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Joule-Thompson Throttling Process
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Joule-Thompson Throttling Process
On high pressure side Wi PiVi On low
pressure side Wf PfVf Total work W
PfVf PiVi Q 0 DU W 0 Uf Ui PfVf
PiVi 0 (Uf PfVf ) (Ui PiVi )
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Enthalpy
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Enthalpy
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Enthalpy
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Enthalpy
True for ideal gas.
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Ideal Gas
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Joule-Thompson Throttling Process