The DAV Class 7 Science Book Solutions and DAV Class 7 Science Chapter 16 Question Answer – Water are essential study tools for DAV public school students in Class 7.
DAV Class 7 Science Ch 16 Question Answer – Water
DAV Class 7 Science Ch 16 Solutions – Water
Something To Know
A. Fill in the blanks.
Question 1.
About ________ of water is present in oceans and seas.
Answer:
97%
Question 2.
Only 0.3% of freshwater available for use is present in rivers,________ and ________
Answer:
lakes, streams
Question 3.
Groundwater is drawn from wells, ________ and ________
Answer:
pond, tube-well
Question 4.
Use of ________ and ________ for irrigation reduces wastage of water.
Answer:
sprinkler, drip irrigation
Question 5.
The network of pipes which carries wastewater to water treatment plant is called ________
Answer:
Sewerage system
B. Write True or False for the following statements.
1. About 97 per cent of water on earth is fresh water and is good for human use.
2. Water occurs in the solid form in glaciers and ice caps.
3. Farmers rely on groundwater for irrigating their crops when there is no rain.
4. Deforestation increases the level of groundwater. ‘
5. More use of ground water causes decrease in water table.
Answer:
1. About 97 per cent of water on earth is fresh water and is good for human use. (False)
2. Water occurs in the solid form in glaciers and ice caps. (True)
3. Farmers rely on groundwater for irrigating their crops when there is no rain. (True)
4. Deforestation increases the level of groundwater. (False)
5. More use of ground water causes decrease in water table. (True)
C. Tick (✓) the correct option.
1. Ocean water is unfit for drinking as it is
(a) Very salty
(b) Tasteless
(c) Too clean
(d) Generally frozen
Answer:
(a) Very salty
2. ‘Rain water harvesting’ can help us to conserve J
(a) Sea water
(b) Fresh water
(c) Rainwater
(d) Pond water
Answer:
(c) Rainwater
3. On the earth, the percentage of water, that is fresh and readily available for use is, nearly .
(a) 99.7%
(b) 97%
(c) 3%
(d) 0.3%
Answer:
(d) 0.3%
4. One of the important factors, that can lead to a scarcity of water, is
(a) Excessive rainfall
(b) Afforestation
(c) Deforestation
(d) Processing of sea water
Answer:
(c) Deforestation
5. Waste water’ is also called
(a) Sewage
(b) Potable water
(c) Water table
(d) Salty water
Answer:
(a) Sewage
D. Answer the following questions in brief.
Question 1.
Name the three forms in which water exists on the earth.
Answer:
Solid (ice), Liquid(water) and Gas (water vapour)
Question 2.
Give the meaning of the term Water table’.
Answer:
The top level of groundwater is called water table.
Question 3.
Name two methods of drawing out groundwater.
Answer:
Tubewell and Handpump
Question 4.
Name two activities which lead to the formation of sewage.
Answer:
Bathing and washing clothes
Question 5.
State any two precautions that can help avoid ‘choking of drains’.
Answer:
Precautions to avoid choking of drains:
- Don’t throw plastic bags in drains
- Don’t throw oil in drain.
E. Answer the following questions.
Question 1.
How is increase in population responsible for shortage of water?
Answer:
Increase in population has resulted in an increased demand for water. Increase in population has also resulted in clearing of forests for various human needs. This has resulted in disturbed recharge of groundwater. On the one hand, the demand for water has increased and on the other, the supply of groundwater has decreased. Thus, it has led to a shortage of water.
Question 2.
Discuss in brief, how ‘rain water harvesting’ can be done.
Answer:
Rainwater harvesting can be done by slight modifications in drainage system from rooftops. The drains from rooftops should be connected to an underground reservoir. This will direct all the rainwater to the underground tank. Water collected in underground tank can be allowed to percolate down the ground. This will help in recharging groundwater. This water can also be purified for later use.
Question 3.
Discuss any two causes that lead to a decrease in ground water level.
Answer:
Two causes which lead to decrease in ground water level are as follows:
(a) Exploitation of groundwater: People exploit groundwater for domestic use as well as for irrigation. This results in depletion of groundwater.
(b) Construction of concrete structures: Concrete structures disturb the natural recharge of groundwater. This also affects the level of groundwater.
Question 4.
How can ‘better management of water resources’ help in conservation of water?
Answer:
Better water management focuses on three aspects which are as follows:
Prevention of wastage of water: Drip irrigation and sprinklers help in preventing wastage of water. We should also prevent wastage of water in our homes. Rainwater harvesting: This helps in recharging the groundwater. Rainwater can also be stored in underground tanks so that it can be used in lean seasons. Wastewater management: Treatment of wastewater helps us in recovering water. This water can be used for irrigation.
Question 5.
Write, in brief, about the basic details and role of the ‘sewerage system’.
Answer:
Sewerage system is a network of sewer lines. Drainage pipes from homes and offices open in drains in the streets. Drains from streets open in main drains which finally go to the wastewater treatment plant. A good sewerage system helps in keeping the city clean. It also helps in recycling of water.
Value Based Question
The school had invited a noted speaker for a talk on ‘Our Environment’. The speaker first gave many suggestions and ideas that could help in improving the environment. She, then, went on to say that though water exists in all its three forms in nature it is the liquid form of water that is most ‘liked’ by all forms of life. In the same way, she said, our habits and activities can be in many ‘forms’ but we should make greater use of only those ‘forms’ that are more liked by the environment.
Question 1.
Suggest at least two ‘habits’ or Values’ that can help in having a better environment.
Answer:
Avoiding wastage of water and maintaining cleanliness in our surroundings.
Question 2.
Write five ‘daily-life related activities’ that usually require the use of water in its liquid form.
Answer:
Bathing, cooking, washing, gardening, mopping
Something to do
Question 1.
Make posters related to water shortage and water conservation and display them in the school.
Answer:
Do it yourself
Question 2.
On the map of India, indicate the place where there is a
(a) Heavy rainfall
(b) Medium rainfall
(c) practically no rainfall
Answer:
Areas around Assam and Western Ghats get heavy rainfall, those around UP and Bihar get medium rainfall and area around Rajasthan get no rainfall.
Question 3.
Try to find the ‘water related problems’ faced by people living in different regions. Take the help of newspaper clippings, encyclopaedia or internet.
Answer:
People living in areas of heavy rainfall often have to suffer floods and problems because of that. People in no rainfall areas suffer from drought and water shortage.
DAV Class 7 Science Chapter 16 Solutions – Water
I. Fill in the blanks.
Question 1.
About ________ part of the earth is covered with water.
Answer:
Three-fourth
Question 2.
________ per cent of total water on earth is available in oceans and seas.
Answer:
97
Question 3.
About ________ per cent of total water is available for human use.
Answer:
One
Question 4.
Drinking water is also known as ________water.
Answer:
Potable
Question 5.
________ is the main source of drinking water for us.
Answer:
Groundwater
II. Tick (✓) the correct option.
1. Which of these states gets heavy rainfall?
(a) Assam
(b) Maharashtra
(c) Rajasthan
Answer:
(a) Assam
2. Which of these states gets scanty rainfall?
(a) Assam
(b) Bihar
(c) Uttar Pradesh
Answer:
(d) Rajasthan
3. Which is the main source of drinking water for us?
(a) River
(b) Lake
(c) Groundwater
Answer:
(c) Groundwater
4. Which of these helps in natural recharge of groundwater?
(a) Desert
(b) Trees
(c) Wind
Answer:
(b) Trees
5. What is the nature of ocean water?
(a) Normal
(b) Saline
(c) Sweet
Answer:
(b) Saline
III. Answer the following questions in brief.
Question 1.
What is the reason of ocean water being unfit for our usage?
Answer:
Ocean water is saline and hence is unfit for our usage.
Question 2.
What is water table?
Answer:
The upper level of groundwater at a place is called water table at that place.
Question 3.
What is rainwater harvesting?
Answer:
Rainwater should be collected in underground tanks and allowed to seep under the ground. This practice is called rainwater harvesting.
Question 4.
What is sewage?
Answer:
The water which flows in the drains is called sewage.
Question 5.
What are the sources of sewage?
Answer:
Households, industries and hospitals.
Question 6.
Why should we not throw cooking oil in drains?
Answer:
Cooking oil contains fat, which can clog the drain. So we should not throw cooking oil in drains.
IV. Answer the following questions.
Question 1.
Briefly explain water scarcity.
Answer:
People in most of the places face acute shortage of water. Due to increased human activities, forests have been cleared on large scale and new constructions have come up. This has disturbed the natural process of recharging the groundwater. Growing human population has resulted in an ever increasing demand for potable water. There is a mismatch between demand and supply for potable water. As a result, water scarcity is a major problem in modern times.
Question 2.
How is water supplied in the cities?
Answer:
Water is supplied in the cities through a system maintained by the civic agencies. Water from rivers or lakes or groundwater is purified in a water treatment plant. This is then supplied to households through a network of pipes.
Question 3.
What are the sources of groundwater? How can it be drawn for use?
Answer:
Well, pond and tube-wells are the means through which we can take groundwater. Rope and bucket is the most common method of drawing water from a well. Hand- pumps or motor operated pumps are used for drawing water from a tube-well.
Question 4.
How are open drains hazardous?
Answer:
Open drains are hazardous in many ways. Open drain becomes a breeding ground for mosquitoes. This can result in spread of diseases; like malaria and dengue. Open drain can also lead to other epidemics; like cholera and typhoid. Open drain is a safety hazard, because any one can fall in that.
Question 5.
Suggest some steps to conserve water.
Answer:
We should follow these steps to conserve water:
(a) Turn off the tap while brushing your teeth.
(b) Leaking tap should be immediately repaired.
(c) Plants should be watered with a mug instead of a pipe.
V. Projects
Question 1.
With the help of a diagram, show various steps of sewage treatment at a sewage treatment plant.
Answer:
Do it yourself.
Question 2.
Make a poster on ‘SAVE WATER’.
Answer:
Do it yourself.