Single-Component Pressure-Volume and Temperature-Volume Diagrams
The van der Waals equation of state for water is used to generate isotherms on a pressure-log volume (P-V) diagram and isobars on a temperature-log volume (T-V) diagram. Sliders change the isotherm temperature on the P-V diagram and the isobar pressure on the T-V diagram. Liquid and vapor are in equilibrium within the phase envelope, which was generated from data for water. The isotherms and isobars have three solutions in the two-phase region, but the only physically-meaningful conditions are the orange dots, which correspond to saturated liquid and saturated vapor. The saturated liquid volume (VL) and the saturated vapor volume (VV) are displayed. The horizontal, dashed orange line (at Psat and Tsat) represents a mixture of liquid and gas. On the P-V diagram, the green area above the orange line is equal to the area below the orange line when plotted on a linear volume scale.

Download the CDF file to view the simulation using the free Wolfram CDF player.