# Phase Transitions - PowerPoint PPT Presentation

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Phase Transitions. The above picture shows a block of solid Ar melting and subliming after exposur to aire at roughly room temperature. . http://en.wikipedia.org/wiki/Phase_transition . Phase Diagram of H 2 O. http://people.virginia.edu/~lz2n/mse209/Chapter9-p1.pdf.

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Phase Transitions

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### Phase Transitions

The above picture shows a block of solid Ar melting and subliming after exposur to aire at roughly room temperature.

http://en.wikipedia.org/wiki/Phase_transition

### Phase Diagram of H2O

http://people.virginia.edu/~lz2n/mse209/Chapter9-p1.pdf

### Examples Chapter 12

• 4.) A system consists of 1024 molecules of water. The initial state is pure vapor at 373 K and atmospheric pressure. The water is heater at constant pressure to T=700K, subsequently compressed isothermally to a pressure of 230 atm, cooled to 373 K a this constant pressure, and finally allowed to expand isothermally to atmospheric pressure. The final state is pure liquid.

• What is the net change in the system’s internal energy?

• What is the net change in the system’s chemical potential?

• 5). The top of Mt. Everest is 8,854 meters above sea level. Calculate the temperature at which water boils at the summit.

• 7). The vapor-pressure curves at the triple point display a cusp (if you look carefully enough, and if the person drawing the diagram was careful enough). Explain why this must be the case.

• a). Specifically, near the triple point for water vg/vl=2.06x105vs/vl=1.09 and the latent heats are 0.47, 0.53 and 0.062 eV/molecule (for vaporization, sublimation and melting respectively).

From J.R. Waldram

“The Theory of Thermodynamics”

### Alloy phase diagram of Cu-Ni

http://people.virginia.edu/~lz2n/mse209/Chapter9-p1.pdf

### Eutectic Phase Diagram

NOTE: at a given overall composition (say: X), both the relative amounts of the two phases (a,b or c,d) AND the composition of one (or possibly both) depend on the temperature

http://www.tulane.edu/~sanelson/geol212/2compphasdiag.html