CH301H - Principles of Chemistry I: Honors
Fall 2013, Unique 52195

Lecture Summary, 3 December 2013

Phase Transitions and Diagrams:  One of the most instructive ways to investigate any given phase is to study transitions is to study the transition between that phase and something else.  This information is wrapped up in a phase diagram, which plots the phase space of an atom or molecule as a function of pressure and temperature.  Phase diagrams describe where transitions between phases occur, which in turn helps us figure out how much energy is necessary to cause a phase transition. 

Aside About Water:  There are three interesting properties of water that are of central importance to life on earth as we know it:

   1.  It has a high melting point compared to other molecules of similar shape and formal weight (for example methane);
   2.  The solid is less dense than the liquid;
   3.  The triple point of water is very near the ambient temperature and pressure of earth.  This means that the solid, liquid, and gas can all appear under near ambient conditions with very small inputs or outputs of energy.

We will see a couple interesting consequences of these properties in this class, but keep this in mind as you move forward in your chemistry and biology classes.