what is vapour pressure

Vapor pressure, also known as equilibrium vapor pressure, is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. It is a measure of the tendency of a material to change into the gaseous or vapor state, and it increases with temperature. The equilibrium vapor pressure is an indication of a liquids thermodynamic tendency to evaporate. A substance with a high vapor pressure at normal temperatures is often referred to as volatile. The vapor pressure of a liquid varies with its temperature, and it increases as the temperature of a liquid or solid increases. Conversely, vapor pressure decreases as the temperature decreases. Vapor pressures are dependent only on temperature and nothing else/Physical_Properties_of_Matter/States_of_Matter/Properties_of_Liquids/Vapor_Pressure). The vapor pressure of a liquid does not depend on the amount of the liquid in the container, and at the same temperature, both samples will have the same vapor pressure/Physical_Properties_of_Matter/States_of_Matter/Properties_of_Liquids/Vapor_Pressure). When a liquid is boiling, its vapor pressure is equal to the external pressure/Physical_Properties_of_Matter/States_of_Matter/Properties_of_Liquids/Vapor_Pressure).