Department of Earth Sciences, University of Bristol
Chemistry for Earth Sciences
Prof. D.M. Sherman
Lecture 11: The Phase Rule and Colligative Properties of Solutions
The phase rule is a powerful tool in geology since it constrains how the phases in a system (e.g.,the minerals in a rock) can vary as a function of the intensive properties (e.g., pressure, temperature, pH..).
The colligative properties of a solution show how boiling and melting temperatures of the solventare affected by composition.
You should be able to:
describe the phase rule
be able to identify the phases, components and degrees of freedom in a system
understand boiling point elevation and freezing point depression and relate these colligative properties to the lowered activity of the solvent.
explain how a the features of a phase diagram involving two solid phases and a melt results
from the colligative property (freezing point depression) of the melt.