Vapor pressure
Vapor Pressure
Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquid's evaporation rate. It relates to the tendency of particles to escape from the liquid (or a solid).
Pronunciation
- IPA: /ˈveɪpər ˈprɛʃər/
Etymology
The term "vapor pressure" is derived from the English words "vapor" and "pressure". "Vapor" comes from the Latin word "vapor", meaning steam or heat, while "pressure" comes from the Latin "pressura", meaning pressing.
Related Terms
- Evaporation: The process by which water changes from a liquid to a gas or vapor.
- Condensation: The change of the physical state of matter from the gas phase into the liquid phase.
- Thermodynamic equilibrium: A state of a system in which all macroscopic properties are unchanging in time.
- Closed system: A physical system that does not allow certain types of transfers in or out of the system.
Understanding Vapor Pressure
Vapor pressure is a measure of the volatility of a substance. It is the pressure at which a vapor is in equilibrium with its liquid or solid form. The higher the vapor pressure of a material at a given temperature, the lower the normal boiling point and thus the faster the evaporation rate. This is because more molecules are escaping from the liquid's surface and becoming vapor.
Factors Affecting Vapor Pressure
Vapor pressure is dependent on the temperature of the system. As the temperature increases, the vapor pressure increases. It is also dependent on the intermolecular forces of the substance. Substances with strong intermolecular forces have lower vapor pressures.
Measurement of Vapor Pressure
Vapor pressure can be measured in the lab using various methods such as the isoteniscope and the effusion method (also known as the Knudsen method).
Applications of Vapor Pressure
Vapor pressure has many practical applications. It is used in the formulation of paints and coatings, in the design of cooling systems and vapor recovery systems, and in weather forecasting.
External links
- Medical encyclopedia article on Vapor pressure
- Wikipedia's article - Vapor pressure
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