Vapour Pressure of Water Vs Temperature

The pressure exerted by the vapor of a liquid (or solid) in equilibrium with its liquid (or solid) phase at a given temperature is called vapour pressure. This applies to a substance in a closed system, where some of the substance has evaporated and established equilibrium. Example: Water in a sealed container at 30°C will develop a vapor pressure of about 4.24 kPa, which is the pressure exerted by the water vapor at equilibrium.

The table below provides the vapour pressure of water up to 374.14°C which is 22.064 MPa (or 3200.1 psia) At this temperature and pressure, the vapor and liquid phases become indistinguishable, and beyond this point, water becomes a supercritical fluid, meaning:

• There is no distinct boiling or condensation.
• Vapor pressure is no longer defined, since there is no phase boundary.