What is vapor pressure?

Vapor pressure refers to the pressure exerted by a solid or liquid in equilibrium with its vapor. This concept is critical in understanding phase transitions between liquid and gas. When a liquid is placed in a closed container, some molecules will escape the liquid phase and enter the vapor (gas) phase. Over time, a dynamic equilibrium is established where the rate of evaporation of the liquid equals the rate of condensation of the vapor back into the liquid. The pressure of the vapor at this equilibrium point is known as the vapor pressure.

Vapor pressure is dependent on temperature; as the temperature increases, more molecules have the energy to escape into the vapor phase, resulting in higher vapor pressure. This property plays a significant role in various scientific and practical applications, such as influencing boiling points and understanding weather phenomena.

The other options describe different principles or phenomena that are not specifically related to vapor pressure. For example, the concept of full condensation pertains to gases and their transition to liquids rather than the equilibrium described by vapor pressure. Vapor pressure also helps determine boiling points but is not itself the pressure at which boiling occurs, and it does not relate to the freezing of liquids.