Procedure : 

Take a beaker of water, keep it on the burner and note the readings of thermometer for every two minutes. 

Observation : 

• We will notice that the temperature of the water rises continuously till it reaches 100° C. 
• Once it reaches 100° C the temperature remains same and a lot of bubbling on the surface takes place. This is called boiling of water. 

Explanation : 

• It happens due to when water is heated the solubility of gases it contains reduces. 
• As a result, bubbles of gas are formed in the liquid. 
• Evaporation of water molecules from the surrounding liquid occurs into these bubbles and they become filled with saturated vapour. 
• At a certain temperature, the pressure of the saturated vapour inside the bubbles becomes equal to the pressure exerted on the bubbles from the outside. 

Conclusion : 

• As a result, these bubbles rise rapidly to the surface and collapse at the surface releasing vapour present in bubbles into air at the surface. This process is called “boiling”. 
• This temperature is called ‘boiling temperature”.