Volatile Definition (Chemistry)

What you need to know about volatility

Water vapor rising from block of ice. A volatile substance converts from liquid or solid into a vapor.
Water vapor rising from block of ice. A volatile substance converts from liquid or solid into a vapor. Ryan McVay / Getty Images

Volatile Definition

In chemistry, the word volatile refers to a substance that vaporizes readily. Volatility is a measure of how readily a substance vaporizes or transitions from a liquid phase to a gas phase. However, the term can also be applied to the phase change from solid state to vapor, which is sublimation. A volatile substance has a high vapor pressure at a given temperature compared with a non-volatile compound.

Examples of Volatile Substances

A volatile material is one that has a high vapor pressure.

  • Mercury is a volatile element. Liquid mercury had a high vapor pressure, readily releasing particles into the air.
  • Dry ice is a volatile inorganic compound that sublimates at room temperature from solid phase into carbon dioxide vapor.
  • Osmium tetroxide (OsO4), is another volatile inorganic compound. Like dry ice, it transitions from the solid phase to vapor phase without becoming a liquid.
  • Many organic compounds are volatile. An example is alcohol. Because volatile substances readily vaporize, they mix with air and may be smelled (if they have an odor). Xylene and benzene are two volatile organic compounds with distinctive scents.

Relationship Between Volatility, Temperature, and Pressure

The higher the vapor pressure of a compound, the more volatile it is. Higher vapor pressure and volatility translate into a lower boiling point.

Increasing temperature increases vapor pressure, which is the pressure at which the gas phase is in equilibrium with the liquid or solid phase. 

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Helmenstine, Anne Marie, Ph.D. "Volatile Definition (Chemistry)." ThoughtCo, Feb. 17, 2017, thoughtco.com/definition-of-volatile-604685. Helmenstine, Anne Marie, Ph.D. (2017, February 17). Volatile Definition (Chemistry). Retrieved from https://www.thoughtco.com/definition-of-volatile-604685 Helmenstine, Anne Marie, Ph.D. "Volatile Definition (Chemistry)." ThoughtCo. https://www.thoughtco.com/definition-of-volatile-604685 (accessed December 12, 2017).