Download Unary Phase Diagrams

Unary and Binary Phase Diagrams
GLY 4200
Fall, 2012
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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
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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
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H2O Diagram
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Terminology
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Water ice
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Silica Phase Diagram
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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
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Carbon Phase
Diagram
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Climate Change Application
• Greenhouse Warming on Terrestrial Planets
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