Free energy and entropy

• The total energy of the gas, U, remains unchanged

  • Same number of particles
  • Same temperature

• The free energy, Fe, and the entropy, S, both change

  • Both are related to the number of states (degrees of freedom)
    • Fe = U – TS

• For our experiment, the total energy U is constant

DFe is the (negative) heat siphoned off into the bath

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