Vapor

Vapor

Nitrogen dioxide gas, a type of vapor.

Phase diagram showing vapor phase.

Binary boiling point diagram illustrating vapor-liquid equilibrium.

Vapor in a cloud chamber.

Crepuscular rays through mist, a form of vapor.

Vapor is a substance in the gaseous phase at a temperature lower than its critical temperature, which means that the vapor can be condensed to a liquid by increasing the pressure without reducing the temperature. Vapors are formed by the evaporation of liquids or the sublimation of solids.

Properties

Vapor is distinguished from an aerosol, which is a suspension of fine solid particles or liquid droplets in air or another gas. A vapor is a substance in the gas phase at a temperature where the same substance can also exist in the liquid or solid state, below the critical temperature of the substance.

Phase transitions

Vapor can be produced from the evaporation of a liquid or from the sublimation of a solid. When a vapor is in contact with its liquid or solid form, the two phases will be in a state of phase equilibrium.

Vapor pressure

The vapor pressure of a substance is the pressure exerted by its vapor when the vapor is in dynamic equilibrium with its liquid or solid form. The vapor pressure of a liquid varies with its temperature, increasing as the temperature rises.

Applications

Vapors are used in various applications, such as in cloud chambers for detecting ionizing radiation, in humidifiers to add moisture to the air, and in distillation processes to separate components of a mixture based on differences in their volatilities.

Related pages

• Gas
• Evaporation
• Sublimation
• Condensation
• Phase transition

References

• Atkins, P. W., & de Paula, J. (2006). Physical Chemistry. Oxford University Press.
• Levine, I. N. (2009). Physical Chemistry. McGraw-Hill.

Vapor

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  Nitrogen dioxide gas

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  Phase diagram

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  Binary boiling point diagram

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  Vapor being used in a cloud chamber

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  Crepuscular rays beam through the mist blown from Takkakaw Falls