CH353 - Physical Chemistry I
Spring 2012, Unique 52135

Lecture Summary, 25 January 2012


Real Gases Continued:  When comparing a real gas to an ideal gas, a very helpful tool is compressibility, Z = VmP/RT.  If Z = 1, the gas is behaving identically to an ideal gas.  If Z > 1, the gas is dominated by repulsive forces, and if Z < 1, the gas is dominated by attractive forces.

First Law of Thermodynamics:  heat + work = Internal Energy

  Work (w).  Thermodynamic work is defined by changes in volume of the thermodynamic system.  By convention, if w < 0, then the system has done work on the surroundings.  If w > 0, then work has been done on the system.

  Heat (q).  Heat is the flow of energy into or out of a system that results in a change in temperature of that system.  Heat and temperature are related through heat capacity, C, which is a property of a material. 

Heat and work are path functions, meaning the magnitude of w and q depend on the path taken between initial and final states.  We will spend much of the next couple days investigating the effects of various thermodynamic paths on heat and work.