CBSE NCERT Board Class 6 Science : Chapter14-Water

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Page No: 145
Exercises

1. 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 _____________ .
Answer:
(a) The process of changing of water into its vapour is called evaporation.
(b) The process of changing water vapour into water is called condensation.
(c) No rainfall for a year or more may lead to drought in that region.
(d) Excessive rains may cause floods.

2. 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 girdle when water is sprinkled on it.
Answer:
(a) Condensation
(b) Evaporation
(c) Condensation
(d) Evaporation
(e) Evaporation

3. 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, is called evaporation.( )
(d) The evaporation of water takes place only in sunlight.( )
(e) Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.( )
Answer:
(a) Not true
(b) Not true
(c) True
(d) Not true
(e) True

Page No: 146

4. Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Answer:
Yes, spreading it near an anghiti or heater will surely help as heater and anghiti are source of heat which vaporize the water of the wet clothes and thus help in drying.

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?
Answer:
The puddle of water seen around the cooled bottle of water is due to the condensation effect as the water vapour present in the air around the bottle get condensed after colliding with bottle.

6. To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Answer:
Water vapour also gets released during exhalation process along with carbon dioxide. These water vapour gets attached with the glasses of the spectacles and then condensed in the presence of air surrounding it and thus making it wet.

7. How are clouds formed?
Answer:
When the air moves up, it gets cooler and cooler and after reaching sufficient heights, the air
becomes so cool that the water vapour present in it condenses to form tiny drops of water called droplets which remain floating in air and thus clouds are formed.

8. When does a drought occur?
Answer:
Drought occurs when an area does not receive rainfall for a period of year or more. Also, the soil continues to lose water by evaporation and transpiration and becomes dry and the ground water may also become scarce which may lead to drought.