Water Class 6 Extra Questions Science Chapter 14

NCERT Extra Questions for Class 6 Science Chapter 14 Water

How Much Water Do We Use?

Question 1.
How much water does a man use daily? Give a rough idea.
Answer:
50-100 litres.

Question 2.
What are the various activities for which water is needed?
Answer:

• Bathing
• Drinking
• Washing clothes
• Toilet etc.

Question 3.
Why is water important for us?
Answer:

• Water regulates body temperature by the process of respiration and evaporation.
• All metabolic reactions in the body take place in aQuestionueous medium.
• It transports minerals and food materials in plant’s and animal’s body.

Question 4.
Why rivers originating from Himalayas do not dry during summer?
Answer:
Rivers originating from the Himalayas do not dry up during summers because they continue to get water from the melting snow on the mountains.

Question 5.
What do you mean by potable water?
Answer:
The water which is suitable for drinking is called potable water.

Where do We Get Water From?

Question 1.
Name some sources of water.
Answer:
Hand pump, tube well, river, pond, lake, ocean, etc.

Question 2.
What is the ultimate source of water?
Answer:
Rain.

Question 3.
What tire the different forms of precipitation?
Answer:
The different forms of precipitation are:

• Rain
• Hail/Snow
• Dew.

Question 4.
Is evaporation endothermic or exothermic process?
Answer:
Evaporation is endothermic process.

Question 5.
Can we use the water in the oceans and seas for drinking and other purposes? Why?
Answer:
No, we cannot use the water in the oceans and seas for drinking and other domestic agricultural and industrial needs because it has much salts dissolved in

Water Cycle

Question 1.
What is water cycle?
Answer:
Water cycle: The water cycle is the journey of water from the oceans and other large bodies of water to the land and from the land back to the water bodies. The water cycle is also called the hydrologic cycle. The main driving forces of the water cycle are the sun’s heat and gravity.

Question 2.
What are the different ways by which water vapour is put into the atmosphere?
Answer:
Water in oceans, lakes and ponds gets evaporated due to atmospheric heat. Factories and thermal power stations produce a lot of steam and put it into the atmosphere. Plants throw out water vapour by transpiration. Animals excrete water vapour through respiration and sweating. All this vapour accumulates in the atmosphere.

Question 3.
How will you show the presence of water vapour in the air?
Answer:
First, take a clean glass and put some ice cubes in it. Keep it in the open air. After some time, small droplets of water will be observed on the outer surface of the glass. This is because water vapour in the air comes in contact with cold surface of glass and condenses. These droplets of water are due to condensation of water vapour present in the air.

Question 4.
Explain the role of plants in adding water vapours into atmosphere.
Answer:
There is yet another process through which water vapour gets transferred into the air. This process involves plants. All plants need water to grow. Plants get this water from the soil, which is absorbed from it by their roots. A part of this water is used by them to prepare their food. Some water is retained by different parts of the plants like roots, stem, leaves, flowers and fruits. However, a large part of this water is released by the plants into air as its vapour. Most of the water lost by the plants in this process is through their leaves. This process is known as transpiration.

Every plant whether it is in a crop field, a forest, on the roadside or in a kitchen garden transpires to give off water vapour. The amount of water vapour that goes into the air through the process of transpiration is very huge. To give an idea, let us consider an example. Suppose a crop of corn has been sown in a plot which is 100 metre long and 100 metre wide. The amount of water that this crop of corn would lose through transpiration during one season would be roughly eQuestionual to water in a 90 centimetre high tank spread over the plot of land.

Water lost through transpiration by wheat plants that give us one kilogram of wheat is roughly 25 large sized buckets full of water, i.e., nearly 500 litres.

Thus, we can see that water vapours get continuously added to air by the plants during the process of transpiration.

Question 5.
Briefly describe the water cycle. Also explain its importance.
Answer:
Water on heating turns into water vapour. Water vapour on cooling gives water again. The change of water from one form to other form over and over again makes the water cycle in nature.

The sun heats up and evaporates the water from oceans, .ponds, lakes and rivers. This water vapour being lighter is carried up by the air. This water vapour gets cooled at height and water droplets are formed. These water droplets form a cloud. When these water droplets in the cloud come close together, they form drops of water. These drops of water may fall on the earth as rain.

The rain is absorbed by the soil. A part of rain water collected in the rivers flows into the sea, where again the evaporation occurs. This completes the water cycle (Fig. 14.8).

Thus, now we know how water gets circulated between the oceans and land through evaporation, transpiration, precipitation and its downhill flow by different routes. This process of circulation of water is known as water cycles. Water cycle helps in maintaining continuous supply of fresh water to all living things on land. No life on land would have been possible without water cycle.

Question 6.
What is the importance of water cycle?
Answer:
The water cycle is important for us because of the following reasons:

• Water cycle helps in regulating weather on earth.
• Water cycle makes water available in its various forms on the earth. The most important is the rainwater.

Question 7.
Draw the flowsheet diagram of water cycle.
Answer:

Question 8.
What is fog? How is it formed?
Answer:
In winters, sometimes condensation of water vapour in air may also take place near the surface of the earth. This water vapour in air near the surface of earth is termed as fog.

Question 9.
We know that water changes into vapour when heated. But it is a common experience that water from wet roads, rooftops and floors disappears without heating. Explain how water changes into its vapour even without heating?
Answer:
During the day time, sunlight falls on the water in oceans, rivers and lakes. The fields, roads, rooftops and other land areas also receive sunlight. The sunlight also carries heat with it. As a result, water from oceans, rivers, lakes and the soil, and other land areas gets continuously changed into its vapour.

Question 10.
Mention the main processes that help in the circulation of water in nature.
Answer:
Main processes that help in circulation of water in nature are evaporation and condensation.
The process of conversion of water into its vapour is known as evaporation. Evaporation of water takes place continuously from oceans, rivers and other water bodies such as lakes and ponds. This water vapour becomes a part of the atmospheric, air.

The water vapour present in the air moves to different places along with the wind. When vapour reaches at a certain height, it gets cooled and turns into very tiny water droplets. These droplets become visible to us in the form of clouds. Ultimately, the water comes down to the surface in the form of rain or snow. This process of conversion of vapour into water is known as condensation.

Circulation of water by evaporation and condensation in this manner is known as water cycle.

Question 11.
What is precipitation? Does precipitation in atmosphere always result in rain?
Answer:
We think of rain or snow when clouds appear in the sky. But, many a times, it does not rain even though the sky may be covered with clouds. We now know that clouds carry small droplets of water in them. It may so happen that:

• Many droplets of water come together to form larger sized drops of water. Such drops of water may become so heavy that they begin to fall. Falling of water drops is called precipitation. If the water during precipitation remains liquid till it reaches the surface of the earth, we have rains.
• Sometimes precipitation may be in the form of hail or snow. Water in a hail or snow is in its frozen or solid form.

Many a times, especially during winter nights, the air near the surface becomes Questionuite cool. As a result, the water vapour present in it condenses to form water droplets. These water droplets appear as dew, which you might have observed on leaves or flowers in the morning during winters.

Question 12.
What is transpiration and write the factors affecting it?
Answer:
A part of water absorbed by the plants is released by plant through their leaves into the air by a process called transpiration.
Transpiration is affected by the following factors:

• Temperature.
• Humidity.
• Windspeed.
• Time of the day.

Activity 2 (page 139)
Take two similar plates. Place one of the plates in sunlight and keep the other under shade. Now, pour eQuestionual amount of water in each of the plates (NCERT Fig. 14.5). You can use a cap of a bottle to measure water. Make sure that water does not spill over. Observe the two plates after every 15 minutes. Does the water seem to disappear? From which plate does it disappear first? What is the source of heat for this evaporation?

Yes, the water seems to disappear. It disappears first from the plate kept in the sunlight. The sun is the source of heat for evaporation.

Back To The Oceans

Question 1.
Explain various paths by which water that falls on land as rain goes back to oceans.
Answer:
Water that falls on the land as rain and snow sooner or later goes back to the ocean This happens in many ways.
Almost all land surfaces are above the level of oceans. When rain falls on the land, the water flows down towards the ocean This flow of water is often in the form of rivers and streams. Sometimes, the water gets trapped in large craters and natural basins on its way to the ocean The rainwater fills up the craters or basins to form lakes. If the lakes or basins have an outlet like a river, the water again begins to flow towards oceans

A part of the rainwater gets absorbed by the ground and seems to disappear in the soil. Some of this water is brought back to the air by the process of evaporation and transpiration. Rest of it continues to seep deeper and deeper under the ground until it is stopped by layers of rock that do not allow water to pass through them. This water is known as groundwater. However, this water may seep through those rocks that let the water to pass through. The water then appears as a spring. Many lakes, ponds and wells are fed by such springs.

Water deposited in the form of snow in mountains also finds its way to an ocean or a sea. Water in rivers, like Ganga and Yamuna, is due to the melting of snow in the lower regions of the Himalayan mountains. All these rivers ultimately terminate in the sea.

What If It Rains Heavily?

Question 1.
In which seasonal most of the rain occurs in our country?
Answer:
Monsoon season.

Question 2.
What are the consequences of large and prolonged rain?
Answer:
Excess of rainfall may lead to rise in the level of water in rivers, lakes and ponds. The water may then spread over large areas causing floods.

Question 3.
What are the major losses due to the flood?
Answer:
In our country, floods cause extensive damage to crops, domestic animals, property and human life.

What Happens If It Does Not Rain For A Long Period?

Question 1.
What would happen if it does not rain in a region for a year or more?
Answer:
It will result in a drought.

Question 2.
What are the consequences of drought?
Answer:
In drought conditions, it is difficult to get food and fodder

Question 3.
What do you understand by epidemic?
Answer:
Epidemic refers to the disease that spreads over a large population of distant areas, e.g., cholera, plague, etc.

How Can We Conserve Water?

Question 1.
Write five sentences to conserve water.
Answer:

1. Water is a precious gift of nature.
2. We should not waste it. Try to ‘save every drop of water’.
3. Always be careful that water tank in your house does not overflow when it is being filled.
4. If we leave the tap running while brushing our teeth, nearly 16 litres of water get wasted. We should fill a mug of water and use that instead.
5. We should not water our garden by drinking water instead we have to reuse the water from washing clothes and cleaning utensils.

Question 2.
What is water pollution and write its causes?
Answer:
The contamination of water due to human activities is known as water pollution. Causes of water pollution are:

• Washing of clothes and utensils.
• Disposal of household sewage and garbage.
• Disposal of industrial effluent.
• Bathing of animals.

Rainwater Harvesting

Question 1.
Write two ways of water harvesting in Delhi. Discuss in brief.
Answer:
Ways of water harvesting in Delhi:

1. Collecting water from the rooftops of houses, flats and other buildings: Rainwater that falls on the rooftops is brought down through pipes and collected in pits. The sides of these pits are lined with concrete. Their bases, however, are unlined and have layers of stone chips, sand and coal tar. These layers sieve the water as it slowly, seeps through into the ground. This raises the level of the groundwater. The groundwater can be used in the future by bringing it up with hand pumps and borings.

2. Collecting water at street corners: Rainwater that falls on tarred roads is completely wasted as it does not seep into the ground. This water can be collected by making holes in the pavement at street corners. The rainwater can then be collected in pits under the pavement and slowly seeped into the ground. Jamia Hamdard University in Delhi has already started using this way of water harvesting.

You will be surprised to learn that even in our city, rainwater is being collected above the ground for direct use. For example, the prisoners of Delhi jail have built a j large cemented pond to collect rainwater. The prisoners use the rainwater collected in this pond for their daily needs. Similarly there is a bus depot that collects and stores rainwater to use for washing buses. Provisions are being made under the flyover at the Dhaula Kuan crossing to harvest the rainwater that collects there and to send this water underground through pipes.

Question 2.
What are the various methods of rainwater harvesting?
Answer:

• Rooftop rainwater harvesting: In this system, the rainwater from the rooftop is collected in a storage tank through pipes.
• A big pit is dug near house for collecting rainwater. This pit is filled with different layers of bricks, coarse gravels and sand or granite pieces.

Question 3.
What are the advantages of water harvesting?
Answer:
Advantages of water harvesting:

• In areas where there is very low rainfall, water harvesting is the only way to reduce’the water shortage.
• There is an increase in the level of groundwater.
• The effects of drought are lessened.
• Places not situated near a river or large lakes have to rely on groundwater. Water harvesting is very important in such areas.
• Water logging of low-lying roads and streets is prevented.
• Soil and water pollution is reduced.

Objective Type Questions

Question 1.
Match the following items given in Column A with that in Column B:

Column A	Column B
(i) Oceans	(a) Are covered with ice
(ii) Lakes	(b) Water drawn from tube well, hand pump and wells
(iii) Rivers	(c) Sources of saline water
(iv) Poles	(d) Results due to excess and continuous rains
(v) Groundwater	(e) Are of both types sweet water and saline water
(vi) Drought	(f) Meant to make up of the water level
(vii) Flooding	(g) The solid form of water
(viii) Water harvesting	(h) Results due to no rain for prolonged time
(ix) Snow	(i) Are sources of sweet water

Answer:

Column A	Column B
(i) Water cycle	(v) Interconversion of water in various forms B
(ii) lakes	(i) conversion of water into steam
(iii) poles	(x) water loss by plants
(v) Ground water	(viii) usually results in rain
(vi) Drought	(ii) feeds nearly all others water sources
(vii) Flooding	(iii) formed during winters due to cooling of atmospheric moisture
(viii) Water Harvesting	(iv) suspend water droplets in atmosphere
(ix) Snow	(vi) ice, water and stream

Question 3.
Fill in the blanks with appropriate words:

1. ………………. is needed for drinking, bathing, washing our clothes and many more functions.
2. Large part of the earth is covered by……………………
3. The water in the oceans is very ……………. in taste.
4. Ice, water and ………………….. are the three states of same material.
5. Water vapours get continuously added to atmosphere due to evaporation and ………………
6. The process of conversion of vapours into liQuestionuid is known as ………………………
7. Falling of …………….. is called precipitation.
8. If water during precipitation remains liquid till it reaches the surface of earth we have …………………………
9. Precipitation in frozen, form is called ……………………
10. Water drops present on grass during winter morning is called ………………………
11. ………………………. carry the water which mainly serves the purpose of drinking.
12. Nearly all the trains in winters run late because of a natural phenomenon known as ………………………
13. ……………… is the basis of life.
14. Most of the water that human beings use come from …………………
15. Oceans act as a ……………………. for large number of plants and animals.

Answers:

1. Water
2. ocean and seas
3. salty
4. steam
5. transpiration
6. condensation
7. water drops
8. rains
9. hail/snow
10. dew
11. Rivers
12. fog
13. Water
14. rivers
15. habitat

Question 4.
State whether the statements given below are True or False

1. Water is needed in producing almost all materials and goods that we use in our everyday life.
2. Oceans are the major sources of sweet water.
3. Water from wet roads, rooftops and other places disappears some time after the rains.
4. The process of condensation is opposite to evaporation.
5. Clouds are the mixture of opaque gases.
6. Condensation near the surface of earth results in fog.
7. Evaporation takes place only in presence of sunlight.
8. Cloud formation occurs only at higher temperatures.
9. Rains feed almost all other sources of water.
10. We should take bath by as much water as we can.
11. Conversion of water into ice, water into vapours and vapours into water, all are chemical processes.
12. Distribution of water is similar in all cold countries.
13. Our body contains about 98% of water.
14. In cold countries, people use water to warm their houses.
15. The groundwater is actually the rainwater.

Answer:

1. True
2. False
3. True
4. True
5. False
6. True
7. False
8. False
9. True
10. False
11. False
12. False
13. False
14. True
15. True

Question 5.
Choose the correct option in the following questions:
(i) Which one is a process in which water changes into vapours in atmosphere?
(a) Evaporation
(b) transpiration
(c) Precipitation
(d) condensation
Answer:
(a) Changing water into vapours is called evaporation.

(ii) Potable water is
(a) ocean water
(b) groundwater at selected places
(c) river water
(d) ponds water
Answer
(b) Potable water is groundwater at specific area.

(iii) Which is not a part of water cycle?
(a) Cloud formation
(b) Rain
(c) Drinking by animals
(d) Sun
Answer:
(c) Drinking by animals is not a part of water cycle.

(iv) Which is a result of condensation of water vapours?
(a) Rain
(b) Snowfall
(c) Hail
(d) Tiny water droplets
Answer:
(d) Water vapour, being brighter, rises up in the atmosphere and cools down. It further condenses to form tiny droplets.

(v) Which one is the purest form of water?
(a) River water
(b) Groundwater
(c) Rainwater
(d) Ocean water
Answer:
(c) Rainwater is the purest form of water.

(vi) Circulation of water between ocean and land is known as
(a) water cycle
(b) rain cycle
(c) water management
(d) water harvesting
Answer:
(a) Constant flow of water from the earth to the atmosphere and back to the earth is known as water cycle if

(vii) The percentage of water in potato is
(a) 88
(b) 75
(c) 90
(d) 95
Answer:
(b) 75% of potato is water.

(viii) Out of these, which is not a source of surface water?
(a) rain water
(b) river and lake water
(c) Spring water
(d) sea water
Answer:
(c) Rainwater, river water and sea water are the examples of surface water.

(ix) Boiling point of water is
(a) 100°C
(c) 101°C
(b) 99°C
(d) 102°C
Answer:
(a) Boiling point of water is 100°C.

(x) Plants release large amount of water vapour into the atmosphere by the process called
(a) evaporation
(b) condensation
(c) precipitation
(d) transpiration
Answer:
(d) Plants release large amount of water vapour into the atmosphere by the process called transpiration.