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Q1 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 _________________.Ans: (a) Evaporation
It is the process of conversion of water into the vapours.
(b) Condensation
The cooling of water vapours and then conversion into water is known as condensation.
(c) Drought
Drought is the condition where lack of water occurs in the excessive amount.
(d) Flood
Flood is the condition in which excess amount of water occurs.
Q2 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.Ans: (a) Condensation
Conversion of water vapours into the water droplets are known as condensation. When the cool water vapours of cold water comes in the contact of environment it becomes hot and convert into the water.
(b) Evaporation
It is because of the water converts into the vapours when hot iron is placed over them.
(c) Condensation
It is because of the conversion of vapours into tiny water droplets.
(d) Evaporation
It is due to evaporation, it mainly happens in high temperature faster.
(e) Evaporation
Due to cooling effect, here evaporation takes place.
Q3 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.( )Ans: (a) False
It is false because water vapours are present in air in every season.
(b) False
Due to high temperature, water evaporates from soil also.
(c) True
This statement is true because conversion of water into vapours is called evaporation.
(d) False
Evaporation of water also occurs on heating.
(e) True
This statement is correct because condensation is the process of conversion of water vapours into tiny droplets of water.
Q4 Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Ans: Yes, we spread it near an heater because near the heater it get hot and the water present in clothes, quickly get converted into the vapours and the clothes will dry soon. As the temperature increases, the process of evaporation will become faster.
Q5 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?
Ans: We see tiny droplets around the cooled bottle of water because, the air around the cooled bottle is warm. So the air around the cooled water bottle condensed when comes in contact with the cool environment. And the tiny droplets can be seen outside the cooled bottle.
Q6 To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Ans: To clean their spectacles, people often breathe out on the glasses to make them wet because the air contains moisture that is coming out of the mouth as compared to the air present around us. That’s why spectacles becomes wet and that will be easy to clean them.
Q7 How are clouds formed?
Ans: Due to the process of evaporation, the water from the soil, pond, lake, mountains, sea and oceans gets converted into water vapours because of high temperature. These water vapours go higher and higher, as we go on the higher altitude the air becomes much cooler. Then the vapours condense or we can say that vapours convert into the tiny water droplets. These tiny droplets remain in the air, then it seems to us as the clouds.
Q8 When does a drought occur?
Ans: Drought is a condition where excessive amount of loss of water occurs. If there is no rainfall for the long time period than soil continuously loses water through the evaporation and transpiration. Water retaining capacity of soil becomes weak. The level of water in soil, oceans, ponds and lakes goes down or we can say dries up and which may leads to the condition called drought.