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Thermal Physics II. Part 2 A) Thermodynamic Potentials & Maxwell Relations B) Statistical Thermodynamics. http://ppewww.ph.gla.ac.uk/~parkes/teaching/TP/TP.html. Chris Parkes. Thermodynamic Potentials & Maxwell Relations. Maxwell Relations from 1 st Laws for U,H,F,G Heat Capacities
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Thermal Physics II Part 2 A) Thermodynamic Potentials & Maxwell Relations B) Statistical Thermodynamics http://ppewww.ph.gla.ac.uk/~parkes/teaching/TP/TP.html Chris Parkes
Thermodynamic Potentials& Maxwell Relations • Maxwell Relations from 1st Laws for U,H,F,G • Heat Capacities • Joule-Kelvin Process • Joule-Kelvin Co-efficients • Inversion Temperature • Inversion Curve for Real Gas • Practical Joule Kelvin Effect • Phase Changes (use of Gibbs function, Phase Diagrams) • Clausius Clapeyron Equation • Vaporisation Curve • 1st order Phase Transitions • 2nd Order phase Transitions
Thermodynamic Potentials Potential Definition First Law Internal Energy: U(S,V) dU=Tds-PdV Enthalpy: H(S,P) H=U+PV dH=Tds+VdP Helmholtz fn: F(T,V) F=U-TS dF=-SdT-PdV Gibbs fn: G(T,P) G=U+PV-TS dG=-SdT+VdP
Maxwell Relations First Law Maxwell Relation dU=Tds-PdV dH=Tds+VdP dF=-SdT-PdV dG=-SdT+VdP
P, V, T P’ Throttling Process Piston P’, V’, T’ P
PVT Surface • Water expands on freezing (as shown here) • Most substances contract
T-P Water • Triple point at 612Pa, 0.010C • -ve slope for ice - water is unusual • Actual phase diagram more complex – • since also crystalline forms of ice, multiple triple points