Question

Paheli asked for a glass of water from Boojho. He gave her a glass of ice-cold water. Paheli observed some water droplets on the outer surface of the glass and asked Boojho how these droplets of water were formed? Which of the following should be Boojho’s answer?
A) Evaporation of water from the glass
B) Water that seeped out from the glass.
C) Evaporation of atmospheric water vapour.
D) Condensation of atmospheric water vapour.

Answer 1

Hint: We all have experienced that when we place a glass of ice-cold water at room temperature there are droplets of water on the surface of the glass. This is because the temperature of the glass is much lower than that of the room temperature.

 Complete step by step answer:
We all have experienced that when we place a glass of ice-cold water at room temperature there are droplets of water on the surface of the glass.
When we keep ice-cold water in a glass, the temperature of the glass becomes lower than that of the room temperature.
There are water vapours present in the atmosphere. These water vapours from the atmosphere condense on the surface of the glass.
This is because the temperature of the glass is much lower than that of the atmospheric temperature.
At lower temperature, the water vapours convert to water droplets.
Thus, the droplets of water on the glass surface are due to the condensation of atmospheric water vapour.
Thus, Boojho’s answer should be condensation of atmospheric water vapour.
Thus, the correct option is (D) condensation of atmospheric water vapour.

Note:The process in which water vapour becomes liquid is known as condensation. Condensation is the reverse process of evaporation. During evaporation, liquid water is converted to water vapours. Condensation of water is an exothermic reaction. When water vapours are converted to liquid, the vapour molecules lose some energy as heat. As energy is lost, the condensation of water vapours is an exothermic reaction.