AP Chemistry
Phase Diagrams of H2O and CO2
Phase Diagram of H2O:
Phase Diagram of CO2:
Important Points:
1. Each region of a phase diagram corresponds to one of the substance’s phases.
2. The lines between the regions represent a phase-transition curve between two phases.
3. Critical point – The point at which the liquid-gas line ends. It is made up of:
a. Critical temperature (Tc) – Two densities are equal and the phase boundary disappears. The
KE of the particles is so high that the vapor cannot be condensed into a liquid regardless of the
applied pressure.
b. Critical pressure (Pc) – The pressure at the critical temperature.
4. Triple Point – The pressure and temperature at which three phases are in equilibrium. A substance can
have more than one triple point.