1. Equilibrium Diagrams
More than one phase (solid, liquid, gas) may be present in equilibrium.
Consider what happens to a single substance when it is heated at constant pressure.
Assume solid contracts upon freezing (not water).
Drawings by J. Seitzman.

2. Heat Substance at Constant pv
Phi
Liquid+Gas
Gas
Solid+ Liquid
Liquid
Plo 4 5 2 3 1
1 - 2 SOLID SOLID + LIQUID LIQUID LIQUID + GAS 5 + GAS

3. Gas/ Superheated Vapor (Saturated) Vapor Dome
Typical T-v Diagram T
Critical Point
Supercritical States
Saturation States = Phase Transitions
Pcrit
Phi
Gas/ Superheated Vapor
(Subcooled) Liquid
Solid+Liquid
Plow
Liquid+Gas
Solid
(Saturated) Vapor Dome
Triple Line
Solid + gas/vapor v

4. Equilibrium Diagram
At high enough pressures in the supercritical region the fluid can have the characteristics of both liquid and gas.
In the liquid/gas region can define the “quality” as:

5. T.D. Properties in Mixed Phase