Explore NCERT Solutions

Exercises:

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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

(b) condensation

(c) drought

(d) flood

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

(b) evaporation

(c) condensation

(d) evaporation

(e) evaporation

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

(b) False

(c) True

(d) False

(e) True

Q4: Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?

Ans: Yes, spreading it near an anghiti or heater it would obsorb more heat from its surrounding, because heat causes faster evaporation. 

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: When cooled bottle is kept out side, the air touches its cold surface. the air around it also becomes cooled, by which the process of condensation takes place causes a puddle of water around it.

Q6: To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.

Ans: The moist air coming out from mouthcondenses on glasses to make glass wet. 

Q7: How are clouds formed?

Ans: The process of condensation plays an important role in the formation of cloud. The upper atmosphere is colder than the earth surface and it around. When water vapour goes higher from the surface of the earth, coming contact of cooled air at sufficient hight it also gets cooler. The air becomes so cool that the water vapour present in it condenses to form tiny drops of water called droplets. It is these tiny droplets that remain floating in air and appear to us as clouds 

Q8: When does a drought occur?

Ans: If it does not rain in a region for a year or more, The soil continues to lose water to lose water by evaporation and transpiration. Since it is not being brought back by rain, the soil becomes dry. The level or water in ponds and wells of region goes down and some of them may even dry up. The ground water may also become scarce. This situation may lead to drought.

Chapter 14. Water 

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Chapter Review:

• Water is essential for life.
• The process of changing of water into its vapour is called evaporation. 
• Water vapour gets added to air by evaporation and transpiration.
• The process of changing water vapour into water is called condensation. 
• Oceans play an important role in supplying the water that we use.
• The water vapour in the air condenses to form tiny droplets of water, which appear as clouds. Many tiny water droplets come together and fall down as rain, snow or hail.
• Rain, hail and snow replenish water in rivers, lakes, ponds, wells and soil.
• The circulation of water between ocean and land is known as the water cycle.
• Excessive rains may cause floods while lack of it for long periods may cause droughts.
• The amount of usable water on earth is limited so it needs to be used carefully.

• The process of condensation plays an important role in bringing water back to the surface of earth.

 

Chapter 14. Water

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1 Mark Questions: 

Ques 1: For what uses, we use water?

Ans: We use water for cooking, drinking, washing clothes, cleaning utensils, irrigating and bathing etc.

Ques 2: what are the main sources of water?

Ans: Ponds, rivers, lakes, wells and Handpump etc.

Ques 3: What part of the Earth is covered by water?

Ans: About two thirds of the Earth is covered with water.

Ques 4: What is water cycle?

Ans: The circulation of water between ocean and land is known as the water cycle.

Ques 5: Which part of sea water is not carried by water vapour during vaporization?

Ans: Water vapour does not carry salt with it.

Ques 6: What is essential thing for vapourisation?

Ans: Heat.

Ques 7: From where does sea water get heat for vapourisation?

Ans: From the sun.

Ques 8: What is water vapour?

Ans: Vapourised water is known as water vapour.

2 marks Questions: 

Ques 9: Even about two third of the Earth is covered with water, but there is lack of drinking water. Give reason.

Ans: The most of the Earth is found in sea and ocean, but they have salty water which is not drinkable.

Ques 10: How does water enter into the air?

Ans: Water vapour enters the air through the processes of evaporation and

transpiration.

Ques 11: What is evaporation?

Ans: The process in which water gets vaporised is known as evaporation.

Ques 12: What is transpiration?

Ans: The process in which plants lose water from leaves and its surface in known as transpiration. 

3 Marks Questions: 

Ques 13: Describe water cycle.

Ans: The ocean water getting vapourised by the sun heat it goes higher from the water surface. At sufficient heights water vapour gets cooler and it condenses to tiny drops of water they fall on the earth as rain. The rain water accumulates in small reservoirs and the most surface water goes to back in the sea and ocean. Thus there creates a cycle of water between ocean and land is known as water cycle.   

Ques 14: How do plants use water?

Ans: Plants need water to grow. Plants use a part of this water to prepare their food and retain some of it in their different parts. Remaining part of this water is released by the plants into air, as water vapour through the process of transpiration.