Unary and Binary Phase Diagrams GLY 4200 Fall, 2012

Unary Diagrams Unary diagrams have a single component We therefore usually choose to plot both P (pressure) and T (temperature) since composition is not a variable Examples Water Silica Carbon

Phase Rule for Unary Systems f = c - p + 2 = 1- p + 2 = 3 - p If one phase is present, there are two degrees of freedom (both T and P) If two phases are present, there is one degree of freedom (either T or P) If three phases are present, there are no degrees of freedom

H2O Diagram Image: h2ophase.gif

Terminology Image: triple_point.gif

Water ice Image: ice-phase-diagram.gif

Silica Phase Diagram Image: silica-phase-diag.gif

Snowflake Obsidian The white patches are crystals of cristobolite, formed at high temperature The magma-crystal mix then erupted, chilling the magma and forming a volcanic glass matrix around the metastable cristobolite, which cooled too quickly to revert to tridymite Source: http://www.lazygecko.com/minerals/infoimages/obsidian.html

Carbon Phase Diagram Image: Carbon_Phase_Diagram.gif

Climate Change Application From David Archer, Global Warming, figure 7.2 Greenhouse Warming on Terrestrial Planets