CH301H - Principles of Chemistry I: Honors
Fall 2017, Unique 50135

Lecture Summary, 5 December 2017

Entropy as disorder:  We worked through a thought experiment in which we defined a property called "microstates."  Microstates (W) are experimentally indistinguishable configurations that all give the same experimentally distinguishable result.  Boltzmann quantified the entropy of a system based on the number of available microstates:

   S = kb ln W

A system will move spontaneously in the direction of increasing number of microstates:

  deltaS = kb ln(Wf/Wi) > 0

This defines both the direction of entropy and provides a molecular level reason for quantifying the magnitude of change in entropy.  This also implies entropy is a state function, because the function is defined only by the number of microstates, which is a property of a system that is independent of how it acquired those microstates.