Evaporation
When a liquid is left exposed to air, its volume decreases gradually. This is due to evaporation. In this process some of the liquid at the surface turns into vapour (or gas) and mixes with the gases in the air.Thus, when a liquid turns into vapour (or gas), it is said to evaporate. We can now define evaporation as follows : The process of a liquid changing into vapour (or gas) even below its boiling point is called evaporation. Evaporation of a liquid can take place even at room temperature, though it is faster at higher temperatures. Whatever be the temperature at which evaporation takes place, the latent heat of vaporisation must be supplied whenever a liquid changes into vapour (or gas). The wet clothes dry due to evaporation of water present in them. And rain water puddles also dry up because of evaporation of water. Common salt is also recovered from sea-water by the process of evaporation.
The process of evaporation can be explained as follows. Some particles in a liquid always have more kinetic energy than the others. So, even when a liquid is well below its boiling point, some of its particles have enough energy' to break the forces of attraction between the particles and escape from the surface of the liquid in the form of vapour (or gas). Thus, the fast moving particles (or molecules) of a liquid are constantly escaping from the liquid to form vapour (or gas).
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1. Classification Of Matter As Solids, Liquids And Gases
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8. Effect of 'Heating' and 'Cooling' on a Saturated Solution
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10. 2. Latent Heat of Vaporisation (Liquid to Gas Change)
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13. 2. Liquid to Gas Change : Boiling (or Vaporisation)
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14. 3. Gas to Liquid Change : Condensation
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15. Why Solids, Liquids and Gases Have Different Properties
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17. 2. The Particles of Matter have Spaces Between Them
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22. 1. Latent Heat of Fusion (Solid to Liquid Change)
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26. 4. The Particles of Matter Attract Each Other
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27. 1. The Particles of Matter are Very, Very Small
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28. 4. Liquid to Solid Change : Freezing
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29. 3. The Particles of Matter are Constantly Moving
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30. Characteristics of Particles of Matter
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32. Two More States of Matter : Plasma and Bose-Einstein Condensate
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38. The Common Unit Of Temperature and Si Unit Of Temperatre
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39. To Show That Solids and Liquids Cannot be Compressed but Gases Can be Compressed Easily
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44. To Show that Liquids do not have a Fixed Shape but they have a Fixed Volume
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45. To Show the Presence of Water Vapour in Air
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49. Gases Can be Liquefied by Applying Pressure and Lowering Temperature
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50. To Show that Gases do not have a Fixed Shape or a Fixed Volume
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