Vapor pressure

Definition

Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature. It indicates the tendency of a substance to evaporate.

5 Must Know Facts For Your Next Test

1. Vapor pressure increases with temperature due to higher kinetic energy of molecules.
2. A liquid boils when its vapor pressure equals the external atmospheric pressure.
3. Substances with high vapor pressures at room temperature are considered volatile.
4. The Clausius-Clapeyron equation relates vapor pressure and temperature for phase changes.
5. In a closed system, dynamic equilibrium is achieved when the rate of evaporation equals the rate of condensation.

Review Questions

• What happens to the vapor pressure of a liquid as its temperature increases?
• How does atmospheric pressure affect the boiling point of a liquid?
• What is meant by dynamic equilibrium in the context of vapor pressure?

Related terms

Boiling Point: The temperature at which a liquid's vapor pressure equals the external atmospheric pressure, causing it to boil.

Clausius-Clapeyron Equation: An equation that describes the relationship between vapor pressure and temperature for phase transitions.

Volatility: A measure of how readily a substance vaporizes; substances with high volatility have high vapor pressures at given temperatures.