- Physical Chemistry I
Spring 2013, Unique 52575
Lecture Summary, 11 February 2013
|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.