Water Vapours in Air

Question 1 How will you show that water vapours are present in air ?

Question 2 Name two scales to measure temperature ?

Question 3 Convert the temperature 300K to Celsius scale ?

Question 4 The boiling point of alcohol is 78°C.What is this temperature on Kelvin scale ?

Presence of water vapours in air

Water vapours comes into the air from the evaporation of water present in ponds,lakes,rivers and oceans.Water vapours is also given out by plants by the process of transpiration.Animals give out water vapours when they breathe out air.

Experiment :We take a steel tumbler and put some well crushed ice into it.Wipe out 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 droplets of water vapours appear on the outer surface of steel tumbler.The air around the steel tumbler contains water vapour in it.When these water vapour come in contact with cold,outside surface of steel tumbler,they condense to form tiny drops of liquid water.

Units of Temperature

The common units of temperature are
1)Degree celsius
2)Kelvin scale

T(K) = T(°C) + 273.15