1. CHEM 433 – 11/1/11 V. Phase Equilibria (Pure Substances)
• Intro & definitions.
• Phase diagrams
- CO2 , H2O, C
• Phase Stability vs. T
READ: CHAPTER 4
HW #6: via – DUE Th.
EXAM #3 on Tuesday – review(s) Monday
Web up to date with review sheet today.

2. Phase: A form of mater, uniform in chemical composition and physical state.
Phase Transition: The spontaneous conversion of one phase to another (e.g. g —> l)
Transition Temperature (Ttrs): Chemical potentials of 2 phases are equal and the 2 phases are in equilibrium
Phase Diagram: Shows regions of P and T in which phases are stable
Phase boundaries: p and T where 2 phases co-exist (in eq. , ’s are =).
Vapor pressure: pressure of vapor in eq. with liquid (the l-v boundary).
Sublimation vapor pressure: pressure of vapor in eq. with solid
(s-v phase boundary)

3. Boiling: A condition of free vaporization throughout the liquid.
Boiling temperature(Tb): T at which vapor pressure equals external pressure
Normal boiling: boiling T at 1 atm external pressure
Standard boiling point: boiling T at 1 bar external pressure.
Freezing/Melting Temperature (Tf): T at which liquid and solid are in EQ at a given p.
Normal/Standard Tf: as above, for 1 atm or 1 bar, respectively.

4. Triple point: Temperature and pressure at which 3 phases coexist (usually s, l, g).
Critical temperature: T when surface between phases disappears (closed system). Density of (l) and (g) become equal!
Critical pressure: vapor pressure at critical temperature.
Supercritical Fluid: The name of the phase above the critical point.

5. Phase Diagram :CO2
How much pressure is needed to liquefy CO2?
What is its normal boiling point?
What is T of “dry ice bath”?
What phase does one have at T = 310K?
Is slope (dP/dT) of solid-liquid boundary “+” or “–”?

6. Phase Diagram :H2O
Notice slope of “Ice I” – liquid boundary – positive or negative?
How many triple points
What is Tc (presumably)?

7. Phase diagram for Carbon (note 1 GPa = 109 Pa = 104 bar)

8. Phase diagram of H2O and the greenhouse effect

9. This picture is a “slice” through the phase diagram at p > T.P.
You re-draw this for:
p < that of triple point
p = to that of triple point