In a closed condition, the pressure of steam that is in equilibrium with a solid or liquid at a certain temperature is called a saturated vapor pressure. Saturated steam pressure is also called steam pressure. The same substance has different vapor pressures at different temperatures and increases with increasing temperature. Different liquid saturated vapor pressures, the saturated vapor pressure of the solvent is greater than the saturated vapor pressure of the solution; for the same substance, the solid saturated vapor pressure is less than the saturated vapor pressure of the liquid.
The vapor pressure changes with temperature. The higher the temperature, the higher the vapor pressure, and of course the type of liquid. At a certain temperature, the pressure generated by steam in equilibrium with the liquid (or solid) state of the same substance is called the saturated vapor pressure, which increases with increasing temperature. For example, the water placed in the cup will become less and less as it evaporates.
If you put pure water in a closed container, take the air above. As the water evaporates continuously, the pressure of the vapor phase above the water surface, that is, the pressure of the water vapor, increases. However, when the temperature is constant, the vapor phase pressure will eventually stabilize at a fixed value, and the vapor phase pressure at this time is called the saturated vapor pressure of water at that temperature.
When the value of the vapor phase pressure reaches the value of the saturated vapor pressure, the water molecules in the liquid phase are continuously vaporized, and the water molecules in the vapor phase are continuously condensed into a liquid, only because the vaporization speed of the water is equal to the condensation speed of the water vapor. The amount of liquid is not reduced, the amount of gas is not increased, and the liquid and gas are in equilibrium. Therefore, when the liquid pure material vapor has a pressure of its saturated vapor pressure, the vapor-liquid two phases reach a phase equilibrium. Saturated vapor pressure is an important property of a substance, and its size depends on the nature and temperature of the substance. The greater the saturated vapor pressure, the more volatile the material is.
