CH353 - Physical Chemistry I
Spring 2015, Unique 51170

Lecture Summary, 24 February 2015


Refocus on the system:  Although the 2nd law provides us with a convenient definition of the direction of spontaneous change, it is cumbersome to have to quantify what is going on in the surroundings as well as the system.  We would like to be able to focus only on the system.  So we derived an expression to combine information on changes in energy and change in entropy during a thermodynamic transformation:

   dG = dH - TdS

Furthermore, we found that if we apply our 2nd law condition of a spontaneous process, we saw that dG < 0, the process will proceed without any additional input of work. 

Free Energy:  Today we used our definitions of Gibbs and Helmholtz free energies to derive a bunch of equations: the natural variables and the Maxwell relations.  These will become very powerful tools to help us solve complex thermodynamic problems in the coming weeks.