What is water vapor



  • 1   Definition of water vapor 
  • 2   Chemical formula for water vapor 
  • 3   Factors affecting water vapor 
  • 4   Importance of water vapor 

Definition of water vapor Water vapor is water when it is in its gaseous state. It is invisible to the naked eye. Water vapor is one of the stages of the atmospheric water cycle, and is constantly produced by evaporation of liquid water or from sublimation of ice. In normal atmospheric conditions water vapor is formed due to evaporation and is usually eliminated through condensation. [1]

The chemical formula of water vapor The chemical formula of water vapor is the same as the chemical formula of water (H2O), but the interaction of water molecules in the gaseous state with each other is less compared with their interaction with each other in the liquid or solid state. [2]

Factors affecting water vapor Water vapor is affected by the following factors: [2]

  • Pressure: The lower the pressure, the lower the water temperature to evaporate, for example, it is possible to get water vapor directly from the ice if the pressure is low.
  • Temperature: Water vapor increases as temperature increases.
  • Relative humidity: the amount of water vapor in the air, and the warmer the air, the more water vapor it carries.

The importance of water vapor 

  • Water vapor is one of the most important greenhouse gases on the Earth’s surface (gases in the atmosphere), and makes up about 90% of them, thus contributing to the heating of the earth and support life. [1]
  • Water vapor contributes to the cooling of the Earth’s surface, because the process of evaporation of liquid water and convert it to water vapor leads to the absorption of heat from the surface of the earth, this heat is released again when condensation of water vapor and the formation of clouds and precipitation . [1]
  • Water vapor is another source of warmth on the Earth’s surface as well as the sun.Water vapor molecules in the lower layers of the atmosphere absorb the radiant heat from the Earth’s surface and then re-release heat in all directions. [3]


  1. ^ Claudette Ojo , “HALOE v2.0 UPPER TROPOSPHERIC WATER VAPOR CLIMATOLOGY”، www.vsgc.odu.edu, Retrieved 7-11-2017, page 1, Edited. 
  2.   “What is Water Vapor? – Definition, Pressure & Formula”, www.study.com, Retrieved 7-11-2017. Edited. 
  3. ↑  “Water Vapor”, www.earthobservatory.nasa.gov, Retrieved 7-11-2017. Edited. 

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