Fill up the blanks in the following.
(A) The process of changing of water into its vapour is called _____________.
(B) The process of changing water vapour into water is called _____________.
(C) No rainfall for a year or more may lead to _____________ in that region.
(D) Excessive rains may cause _____________.
State for each of the following whether it is due to evaporation or condensation.
(A) Water drops appear on the outer surface of a glass containing cold water.
(B) Steam rising from wet clothes while they are ironed.
(C) Fog appearing on a cold winter morning.
(D) Blackboard dries up after wiping it.
(E) Steam rising from a hot griddle when water is sprinkled on it.
Which of the following statements are “true”?
(A) Water vapour is present in air only during the monsoon.
(B) Water evaporates into air from oceans, rivers and lakes but not from the soil.
(C) The process of water changing into its vapour form is called evaporation.
(D) Evaporation of water takes place only in sunlight.
(E) Water vapour condense to form tiny droplets of water in the upper layers of air where it is cooler.
(A) False – Water vapour is present in air in all seasons.
(B) False – Water evaporates into the air from the soil also.
(D) False – Evaporation of water also takes place upon heating and in shade during daytime.
Suppose you want to dry your school uniform quickly, would spreading it near an angithi or heater help? If yes, how?SOLUTION:
Yes, spreading of school uniform near an angithi or heater helps to dry it quickly. It is because an angithi or heater provides heat which evaporates water present in the clothes.Q 5.
Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?SOLUTION:
We see puddle of water around the cooled bottle of water after some time because of condensation. The air when comes in contact with the cold surface of the bottle containing chilled water it gets cooled and as a result the water vapour present in air condenses on the surface of the bottle.Q 6.
To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.SOLUTION:
The glasses become wet because the air we breathe out is warm and contains water vapours which condense on the surface of glass in the form of water droplets. Thus, making the glass surface wet.Q 7.
How are clouds formed?SOLUTION:
Due to evaporation of water from various water bodies, open fields and transpiration from the surface of leaves, water vapours are formed in the air. As this air moves up, it gets cooler and at certain height, it becomes cool enough for condensation. There, the water vapours present in the air condense into tiny droplets of water. These tiny droplets of water remain floating in the air and appear to us as clouds.Q 8.
When does a drought occur?SOLUTION:
Drought occurs when there is scanty rainfall or no rainfall for a year or more in a particular region. As the lakes and ponds dry up due to continuous evaporation, the water level lowers down. The soil continues to lose water by evaporation and transpiration and ultimately becomes dry. This condition leads to drought.