Thermo & Stat Mech - Spring 2006 Class 4 1 Thermodynamics and Statistical Mechanics Does the Internal Energy of a Real Gas Depend Only on Temperature?

Thermo & Stat Mech - Spring 2006 Class 42 Change of Phase First Law is: du = đq – Pdv For a finite change at constant temperature  u = q – P  v At transition, u 2 – u 1 = l 12 – P(v 2 – v 1 ) l 12 = (u 2 + Pv 2 ) – (u 1 + P v 1 ) l 12 = h 2 – h 1

Thermo & Stat Mech - Spring 2006 Class 43 Enthalpy and Latent Heat Enthalpy is defined as: h = u + Pv

Thermo & Stat Mech - Spring 2006 Class 44 Enthalpy is a State Function

Thermo & Stat Mech - Spring 2006 Class 45 Does u depend on Volume? If u = u(T, v), then,

Thermo & Stat Mech - Spring 2006 Class 46 From Cyclical Relation

Thermo & Stat Mech - Spring 2006 Class 47 Gay-Lussac–Joule Experiment

Thermo & Stat Mech - Spring 2006 Class 48 Gay-Lussac–Joule Results

Thermo & Stat Mech - Spring 2006 Class 49 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.

Thermo & Stat Mech - Spring 2006 Class 410 Joule-Thompson Throttling Process

Thermo & Stat Mech - Spring 2006 Class 411 Joule-Thompson Throttling Process On high pressure side: W i = – P i V i On low pressure side: W f = + P f V f Total work: W = P f V f – P i V i Q = 0 =  U + W 0 = U f – U i + P f V f – P i V i 0 = (U f + P f V f ) – (U i + P i V i )

Thermo & Stat Mech - Spring 2006 Class 412 Enthalpy

Thermo & Stat Mech - Spring 2006 Class 413 Enthalpy

Thermo & Stat Mech - Spring 2006 Class 414 Enthalpy

Thermo & Stat Mech - Spring 2006 Class 415 Enthalpy True for ideal gas.

Thermo & Stat Mech - Spring 2006 Class 416 Ideal Gas

Thermo & Stat Mech - Spring 2006 Class 417 Joule-Thompson Throttling Process