Phase+Diagrams

A **phase diagram** is a graphical way to represent the conditions under which equilibria exist between different states of matter. This includes liquid-gas equilibria, solid-liquid equilibria, and even solid-gas equilibria.

The blue area in the above diagram represents the gas phase, the yellow area the liquid phase, and the cyan area the solid phase. The green region represents the critical region in the phase diagram where it is not possible to distinguish between gas and liquid. Words in italics represent the process (double arrows). Letters in Arial mark special points on the graph and normal test labels the regions and the axes Normal Freezing Point & Normal Boiling Point).

A phase diagram works somewhat like a coordinate plane in math. You find a "point" on the diagram by finding where the temperature and pressure "coordinates" meet. Wherever this "point" is decides what phase the substance is in. If you find that the "point" is in the yellow area, then the substance is a liquid at that temperature and pressure. If the "point" lies on the border between two areas, then it is at a freezing point, boiling point, or a state of sublimation. This results in the substance existing partially in both states. An example is at the border of the liquid and gas areas, where the boiling point line is. An example could be when liquid water boils, is changes to water vapor, therefore existing as two phases at once. The same idea is applied for a solid melting and a solid sublimating into a gas. All of these lines work the other way too (evaporation/condensation, melting/freezing, and sublimation/deposition). Point T is a special point called the triple point where the substance could be in any or all of the three states.



This is a phase diagram for graphite. Graphite is very common, but when superheated at high pressures, it forms a diamond. It's evident from this phase diagram that an enormous amount of pressure is required for diamond to form. That amount of pressure does not occur regularly, so diamonds are very rare.

http://www.chem.queensu.ca/people/faculty/mombourquette/FirstYrChem/slg/phasdiag.gif http://upload.wikimedia.org/wikipedia/commons/3/30/Phase-diag.svg http://bhs.smuhsd.org/science-dept/marcan/apchemistry/h2ophase.gif http://bhs.smuhsd.org/science-dept/marcan/apchemistry/phasediagrampic.jpg [|http://content.answers.com/main/content/] Bursten, Brown, & LeMay. __Chemistry: The Central Science, 9th Edition.__ (
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