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[[File:kettle-653673_640.jpg|360px|thumb|right|Figure 1. Although invisible, water vapour is one component of the [[wet steam]] released by a boiling kettle, the visible portion is microscopic droplets of water suspended in the air.<ref>Pixabay. (September 3, 2015). ''Kettle Steam'' [Online]. Available: https://pixabay.com/p-653673/?no_redirect</ref>]]
[[File:kettle-653673_640.jpg|360px|thumb|right|Figure 1. Although invisible, water vapour is one component of the [[wet steam]] released by a boiling kettle, the visible portion is microscopic droplets of water suspended in the air.<ref>Pixabay. (September 3, 2015). ''Kettle Steam'' [Online]. Available: https://pixabay.com/p-653673/?no_redirect</ref>]]


<onlyinclude>'''Water vapour''' is [[water]] in [[gas]]eous instead of [[liquid]] form.  
<onlyinclude>'''Water vapour''' is [[water]] in a [[gas]]eous state instead of a [[liquid]] state.  
It can be formed either through a process of [[evaporation]] or [[sublimation]]. Unlike [[cloud]]s, fog, or mist which are simply suspended particles of liquid water in the [[air]], water vapour itself cannot be seen because it is in gaseous form.</onlyinclude><ref name=climap/>
It can be formed either through a process of [[evaporation]] or [[sublimation]]. Unlike [[cloud]]s, fog, or mist, which consist of tiny, suspended particles of liquid water in the [[air]], water vapour itself cannot be seen because it is in gaseous form.</onlyinclude><ref name=climap/>


Water vapour in the [[atmosphere]] is often below its [[boiling point]]. When water is boiled the water evaporates much faster and makes [[steam]]. Steam often has droplets of water, which is what is seen water is boiling. Since both water droplets and water vapour are present, this is called [[wet steam]] (also called [[wet vapour]]). As the mixture gets hotter, the water droplets go away and it becomes [[dry steam]] (also called [[dry vapour]]).<ref name=Bhatt> Bhattacharjee, ''Thermodynamics: an interactive Approach''. Pearson, 2015.</ref> [[Power plant]]s use water vapour in the form of steam (dry is better, but wet is used too) as a [[working fluid]] to turn their [[turbine]]s to make [[electricity]].  
Water vapour in the [[atmosphere]] is often below its [[boiling point]]. When water is boiled, it evaporates much more rapidly and produces [[steam]]. Steam often contains tiny droplets of liquid water, which are what is seen when water is boiling. Since both water droplets and water vapour are present, this is called [[wet steam]] (also called [[wet vapour]]). As the mixture gets hotter, the liquid water droplets evaporate, producing [[dry steam]] (also called [[dry vapour]]).<ref name=Bhatt> Bhattacharjee, ''Thermodynamics: an interactive Approach''. Pearson, 2015.</ref> Many [[power plant]]s use water vapour in the form of steam as a [[working fluid]] to drive [[turbine]]s that generate [[electricity]]. Dry steam performs better, although wet steam is also used.  


==Atmospheric Water Vapour==
==Atmospheric Water Vapour==
Water vapour is important for a number of different reasons, but its presence in the [[atmosphere]] is one of the most important. Water vapour is present within the atmosphere in varying amounts but is a vital component of the [[hydrologic cycle]]. In the atmosphere, water vapour can exist in trace amounts or even make up as much as 4% of the atmosphere. This concentration depends largely on where the water vapour levels are measured. On average, the value of water vapour in the atmosphere is 2-3%. In arid or very cold locations - such as polar regions - the amount of water vapour in the air is much lower.<ref name=atm>The Weather Prediction. (September 3, 2015). ''Atmospheric Water Vapour'' [Online]. Available: http://www.theweatherprediction.com/habyhints/40/</ref>  
Water vapour is important for many reasons, but its presence in Earth's [[atmosphere]] is one of the most important roles. Water vapour is present within the atmosphere in varying amounts but is a vital component of the [[hydrologic cycle]]. Atmospheric water vapour ranges from trace amounts to approximately 4% of the atmosphere by volume, depending on location and atmospheric conditions.<ref>National Weather Service, National Oceanic and Atmospheric Administration. (July 3, 2026). ''Atmosphere'' [Online]. Available: https://prod-01-alb-www-noaa.woc.noaa.gov/jetstream/atmosphere</ref> This concentration depends largely on where the water vapour levels are measured. On average, water vapour makes up about 2-3% in the atmosphere. In arid or very cold locations, such as polar regions, the amount of water vapour in the air is much lower.<ref name=atm>The Weather Prediction. (September 3, 2015). ''Atmospheric Water Vapour'' [Online]. Available: http://www.theweatherprediction.com/habyhints/40/</ref>  


Even on a clear day, water vapour exists in the atmosphere as an invisible gas - unlike clouds which are droplets of liquid water that can be seen. If the conditions are right, water vapour in the air can collect on small particles of dust, salt, or [[smoke]] in the air to form small droplets. These droplets gradually increase in size and over time become various forms of [[precipitation]]. Since water vapour is so prominent in the atmosphere and forms precipitation, water vapour is a major component of the hydrologic cycle. When [[water storage|water holding areas]] are heated by the [[Sun]], some of the water being held evaporates and becomes vapour, powering the cycle.<ref>USGS. (September 10, 2015). Precipitation - The Water Cycle [Online]. Available: http://water.usgs.gov/edu/watercycleprecipitation.html</ref>
Even on a clear day, water vapour exists in the atmosphere as an invisible gas, unlike clouds, which consist of visible droplets of liquid water. If conditions are right, water vapour can condense onto tiny particles of dust, salt, or [[smoke]], forming small water droplets. As these droplets grow larger, they can eventually form [[precipitation|precipitations]] such as rain, snow, sleet, or hail. Since water vapour plays a central role in forming precipitation, it is a major component of the hydrologic cycle. When the [[sun]] heats [[water storage|water holding areas]], some of the water evaporates into the atmosphere as water vapour, helping to drive the cycle.<ref>USGS. (September 10, 2015). Precipitation - The Water Cycle [Online]. Available: http://water.usgs.gov/edu/watercycleprecipitation.html</ref>


In addition to being created by evaporating water, plants are capable of producing water vapour through a process of [[transpiration]].  
In addition to evaporation, plants release water vapour into the atmosphere through a process known as [[transpiration]].  


==Product of Combustion==
==Product of Combustion==
When [[hydrocarbon]]s undergo [[combustion]], water is created by the chemical reactions. However, the high temperatures mean that the water is in its gaseous form: water vapour. An example of a hydrocarbon combustion reaction is shown below to illustrate how water is created during this process.
When [[hydrocarbon]]s undergo [[combustion|combustions]], one of the products of the chemical reaction is water. However, because combustion occurs at high temperatures, the water is produced in its gaseous form, known as water vapour. An example of a hydrocarbon combustion reaction is shown below to illustrate how water is produced during combustion.


[[File:combustion_of_methane.jpg|800px|thumbnail|center|Figure 2. Methane combining with 2 oxygen to form carbon dioxide, two water molecules (in the form of water vapour) and heat.<ref name="image">American Chemical Society. (September 3, 2015).  ''Methane and oxygen react'' [Online]. Available: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]</ref>]]
[[File:combustion_of_methane.jpg|800px|thumbnail|center|Figure 2. Methane combining with 2 oxygen to form carbon dioxide, two water molecules (in the form of water vapour) and heat.<ref name="image">American Chemical Society. (September 3, 2015).  ''Methane and oxygen react'' [Online]. Available: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]</ref>]]


Since water vapour is released when hydrocarbons are burned, water vapour is a fairly large component of the [[flue gas]]es released from [[coal]] fired [[power plant]]s or [[natural gas power plant]]s. A surprisingly large amount of water is released when coal is burned. For example, when burning [[bituminous coal]] roughly 0.4 [[kilogram]]s of water are produced for every kilogram of coal burned. This means that [[tonne]]s of water are be produced per hour at a large-scale coal fired power plant.  
Since water vapour is released when hydrocarbons are burned, it is a significant component of the [[flue gas]]es released by [[coal]]-fired [[power plant]]s or [[natural gas power plant]]s. A substantial amount of water vapour is produced when coal is burned. For example, when [[bituminous coal]] is burned, approximately 0.4 [[kilogram]]s of water are produced for every kilogram of coal burned. This means that large coal-fired power plants can produce many [[tonne]]s of water vapour every hours.  


==Climate Impacts==
==Climate Impacts==
Water vapour moves across the Earth's surface, cycling through a variety of storage areas. It is this cycling that shapes the [[climate]] of different regions across the globe, providing precipitation and supporting life. As the climate changes, the distribution and cycling of water vapour changes as well.<ref name=quest>QUEST. (September 10, 2015). ''Water Vapour - Positive Feedback Cycle'' [Online]. Available: http://science.kqed.org/quest/2014/12/12/water-vapors-role-in-climate-change/</ref>
Water vapour moves continuously throughout the Earth's surface as part of the water cycle, cycling between the atmosphere, oceans, land, and living organisms.<ref>National Oceanic and Atmospheric Administration. (July 3, 2026). ''The Water Cycle'' [Online]. Available: <nowiki>https://www.noaa.gov/education/resource-collections/freshwater/water-cycle</nowiki></ref> This continuous cycling influences regional [[climate|climates]], produces precipitation, and helps sustain life on Earth. As the climate changes, the distribution and cycling of water vapour changes as well.<ref name=quest>QUEST. (September 10, 2015). ''Water Vapour - Positive Feedback Cycle'' [Online]. Available: http://science.kqed.org/quest/2014/12/12/water-vapors-role-in-climate-change/</ref>


Water vapour is actually the most abundant [[greenhouse gas]] in the atmosphere, and the most potent of all the greenhouse gases as a result of its [[chemical]] structure. Its presence accounts for around two thirds of the natural [[greenhouse effect]].<ref name=climap>Climap. (September 3, 2015). ''Water Vapour'' [Online]. Available: http://climap.net/water-vapor</ref> In the past there has been debate over how severe an impact water vapour has on [[global warming]], but recently studies have confirmed that the amplification that water vapour has on heat is strong enough to double climate warming caused by increased CO<sub>2</sub> levels.<ref>Kathryn Hansen, NASA. (September 3, 2015). ''Water Vapor Confirmed as Major Player in Climate Change'' [Online]. Available: http://www.nasa.gov/topics/earth/features/vapor_warming.html</ref>
Water vapour is actually the most abundant [[greenhouse gas]] in the atmosphere. Its [[chemical]] structure allows it to absorb heat radiated from Earth's surface, helping to maintain the planet's natural [[greenhouse effect]]. Water vapour is responsible for approximately one-half to two-thirds of Earth's natural greenhouse effect, depending on the method of estimation.<ref name="climap">National Aeronautics and Space Administration. (July 3, 2026). ''Steamy Relationships: How Atmospheric Water Vapor Amplifies Earth's Greenhouse Effect'' [Online]. Available: https://science.nasa.gov/earth/climate-change/steamy-relationships-how-atmospheric-water-vapor-amplifies-earths-greenhouse-effect/</ref> Climate models and observations show that increasing atmospheric water vapour amplifies the [[global warming]] caused by rising concentrations of carbon dioxide and other greenhouse gases. This water vapour feedback is estimated to approximately double the global warming that would occur from carbon dioxide alone.<ref name="climap" />


As a greenhouse gas, water vapour serves creates a [[Positive climate feedback|positive feedback cycle]] for global warming. This means that the warmer the world gets, the more water vapour will exist in the air as evaporation rates from [[ocean]]s, lakes, and streams increase.<ref name=quest/> Since there is then more water vapour in the air, the water vapour itself contributes to more warming. Human activities do not increase the overall water vapour content in the atmosphere, but human activities can cause more water to evaporate as a result of increased temperature of the atmosphere. Thus [[anthropogenic]] warming is enhanced by a greater water vapour content in the atmosphere.<ref name=climap/>
As a greenhouse gas, water vapour creates a [[Positive climate feedback|positive feedback cycle]] for global warming. As Earth's temperature increases, evaporation from [[ocean]]s, lakes, and streams also increases, adding more water vapour to the atmosphere. The additional water vapour traps more heat, which leads to further warming.<ref name=quest/> Human activities do not directly increase atmospheric water vapour in the same way they increase carbon dioxide. Instead emissions of greenhouse gases warm the atmosphere, which increases evaporation and allows the atmosphere to hold more water vapour. Thus [[anthropogenic]] warming is enhanced by the greater water vapour content in the atmosphere.<ref name=climap/>
 
== For Further Reading ==
 
* [[Hydrologic cycle]]
* [[Greenhouse effect]]
* [[Flue gas]]
* [[Working fluid]]
* Or explore a [[Special:Random|random page]]


==References==
==References==
{{reflist}}[[Category:Uploaded]]
{{reflist}}[[Category:Uploaded]]

Latest revision as of 20:43, 4 August 2026

Figure 1. Although invisible, water vapour is one component of the wet steam released by a boiling kettle, the visible portion is microscopic droplets of water suspended in the air.[1]

Water vapour is water in a gaseous state instead of a liquid state. It can be formed either through a process of evaporation or sublimation. Unlike clouds, fog, or mist, which consist of tiny, suspended particles of liquid water in the air, water vapour itself cannot be seen because it is in gaseous form.[2]

Water vapour in the atmosphere is often below its boiling point. When water is boiled, it evaporates much more rapidly and produces steam. Steam often contains tiny droplets of liquid water, which are what is seen when water is boiling. Since both water droplets and water vapour are present, this is called wet steam (also called wet vapour). As the mixture gets hotter, the liquid water droplets evaporate, producing dry steam (also called dry vapour).[3] Many power plants use water vapour in the form of steam as a working fluid to drive turbines that generate electricity. Dry steam performs better, although wet steam is also used.

Atmospheric Water Vapour

Water vapour is important for many reasons, but its presence in Earth's atmosphere is one of the most important roles. Water vapour is present within the atmosphere in varying amounts but is a vital component of the hydrologic cycle. Atmospheric water vapour ranges from trace amounts to approximately 4% of the atmosphere by volume, depending on location and atmospheric conditions.[4] This concentration depends largely on where the water vapour levels are measured. On average, water vapour makes up about 2-3% in the atmosphere. In arid or very cold locations, such as polar regions, the amount of water vapour in the air is much lower.[5]

Even on a clear day, water vapour exists in the atmosphere as an invisible gas, unlike clouds, which consist of visible droplets of liquid water. If conditions are right, water vapour can condense onto tiny particles of dust, salt, or smoke, forming small water droplets. As these droplets grow larger, they can eventually form precipitations such as rain, snow, sleet, or hail. Since water vapour plays a central role in forming precipitation, it is a major component of the hydrologic cycle. When the sun heats water holding areas, some of the water evaporates into the atmosphere as water vapour, helping to drive the cycle.[6]

In addition to evaporation, plants release water vapour into the atmosphere through a process known as transpiration.

Product of Combustion

When hydrocarbons undergo combustions, one of the products of the chemical reaction is water. However, because combustion occurs at high temperatures, the water is produced in its gaseous form, known as water vapour. An example of a hydrocarbon combustion reaction is shown below to illustrate how water is produced during combustion.

Figure 2. Methane combining with 2 oxygen to form carbon dioxide, two water molecules (in the form of water vapour) and heat.[7]

Since water vapour is released when hydrocarbons are burned, it is a significant component of the flue gases released by coal-fired power plants or natural gas power plants. A substantial amount of water vapour is produced when coal is burned. For example, when bituminous coal is burned, approximately 0.4 kilograms of water are produced for every kilogram of coal burned. This means that large coal-fired power plants can produce many tonnes of water vapour every hours.

Climate Impacts

Water vapour moves continuously throughout the Earth's surface as part of the water cycle, cycling between the atmosphere, oceans, land, and living organisms.[8] This continuous cycling influences regional climates, produces precipitation, and helps sustain life on Earth. As the climate changes, the distribution and cycling of water vapour changes as well.[9]

Water vapour is actually the most abundant greenhouse gas in the atmosphere. Its chemical structure allows it to absorb heat radiated from Earth's surface, helping to maintain the planet's natural greenhouse effect. Water vapour is responsible for approximately one-half to two-thirds of Earth's natural greenhouse effect, depending on the method of estimation.[2] Climate models and observations show that increasing atmospheric water vapour amplifies the global warming caused by rising concentrations of carbon dioxide and other greenhouse gases. This water vapour feedback is estimated to approximately double the global warming that would occur from carbon dioxide alone.[2]

As a greenhouse gas, water vapour creates a positive feedback cycle for global warming. As Earth's temperature increases, evaporation from oceans, lakes, and streams also increases, adding more water vapour to the atmosphere. The additional water vapour traps more heat, which leads to further warming.[9] Human activities do not directly increase atmospheric water vapour in the same way they increase carbon dioxide. Instead emissions of greenhouse gases warm the atmosphere, which increases evaporation and allows the atmosphere to hold more water vapour. Thus anthropogenic warming is enhanced by the greater water vapour content in the atmosphere.[2]

For Further Reading

References

  1. ↑ Pixabay. (September 3, 2015). Kettle Steam [Online]. Available: https://pixabay.com/p-653673/?no_redirect
  2. ↑ 2.0 2.1 2.2 2.3 National Aeronautics and Space Administration. (July 3, 2026). Steamy Relationships: How Atmospheric Water Vapor Amplifies Earth's Greenhouse Effect [Online]. Available: https://science.nasa.gov/earth/climate-change/steamy-relationships-how-atmospheric-water-vapor-amplifies-earths-greenhouse-effect/
  3. ↑ Bhattacharjee, Thermodynamics: an interactive Approach. Pearson, 2015.
  4. ↑ National Weather Service, National Oceanic and Atmospheric Administration. (July 3, 2026). Atmosphere [Online]. Available: https://prod-01-alb-www-noaa.woc.noaa.gov/jetstream/atmosphere
  5. ↑ The Weather Prediction. (September 3, 2015). Atmospheric Water Vapour [Online]. Available: http://www.theweatherprediction.com/habyhints/40/
  6. ↑ USGS. (September 10, 2015). Precipitation - The Water Cycle [Online]. Available: http://water.usgs.gov/edu/watercycleprecipitation.html
  7. ↑ American Chemical Society. (September 3, 2015). Methane and oxygen react [Online]. Available: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]
  8. ↑ National Oceanic and Atmospheric Administration. (July 3, 2026). The Water Cycle [Online]. Available: https://www.noaa.gov/education/resource-collections/freshwater/water-cycle
  9. ↑ 9.0 9.1 QUEST. (September 10, 2015). Water Vapour - Positive Feedback Cycle [Online]. Available: http://science.kqed.org/quest/2014/12/12/water-vapors-role-in-climate-change/
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