Thermodynamics and Statistical Mechanics

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Thermodynamics and Statistical Mechanics

• The Third Law of Thermodynamics

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Statements of Third Law

• All reactions in a liquid or solid in thermal
  equilibrium take place with no change of entropy
  in the neighborhood of absolute zero.
• (Nernst)
• The entropy of a true equilibrium state of a
  system at absolute zero is zero.
• (Planck)

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Statements of Third Law

• It is impossible to reduce the temperature of a
  system to absolute zero using a finite number of
  processes.
• (Unattainability statement)

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Entropy
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Nernst Postulate
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Planck
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Equivalence of Statements

• Assume that the unattainability statement of the
  third law is valid, and show that it leads to the
  Nernst statement.
• DS0 S01 S02 0

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Equivalence of Statements
Consider adiabatic cooling
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Adiabatic Cooling Plot
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Can Achieve T 0
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Real Cooling
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Consequences of Third Law
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Consequences of Third Law
Clausius-Clapeyron equation
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Consequences of Third Law