To Show the Presence of Water Vapour in Air
There is always some water vapour in the air around us (which we cannot see). The amount of water vapour in air keeps on changing. Water vapour comes into the air from the evaporation of water present in ponds, lakes, rivers and oceans. Water vapour is also given out by plants by the process of transpiration (evaporation from leaves). Animals give out water vapour when they breathe out air. Land also gives water vapour on being warmed by the sun. All this water vapour goes into the air around us. We will now describe an experiment to demonstrate that water vapour is present in air.
The presence of water vapour in air can be shown by the following experiment. We take a steel tumbler and put some well crushed ice into it (see Figure 57). Wipe the tumbler from outside with a piece of clean,dry cloth, so as to make its outer surface completely dry. Allow the ice containing steel tumbler to stand undisturbed for about five minutes. A large number of tiny drops of water appear on the outer surface of steel tumbler (see Figure 57). This happens as follows: The air around the steel tumbler contains water vapour in it. When these water vapour come in contact with the cold, outside surface of steel tumbler, they condense to form tiny drops of liquid water. So, the formation of drops of water on the outside surface of a tumbler containing crushed ice, shows the presence of water vapour in air.
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3. 2. Liquid to Gas Change : Boiling (or Vaporisation)
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4. 2. Latent Heat of Vaporisation (Liquid to Gas Change)
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5. Effect of 'Heating' and 'Cooling' on a Saturated Solution
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6. Classification Of Matter As Solids, Liquids And Gases
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9. Why Solids, Liquids and Gases Have Different Properties
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14. 2. The Particles of Matter have Spaces Between Them
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15. 1. Solid to Liquid Change : Melting
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16. 3. Gas to Liquid Change : Condensation
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20. 1. Latent Heat of Fusion (Solid to Liquid Change)
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24. 1. The Particles of Matter are Very, Very Small
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26. 4. The Particles of Matter Attract Each Other
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28. 3. The Particles of Matter are Constantly Moving
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29. Characteristics of Particles of Matter
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30. 4. Liquid to Solid Change : Freezing
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31. 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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