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DAV Class 7 Science Chapter 16 Water Question Answer
DAV class 7 Science chapter 16 water question answer is given below. Here DAV class 7 Science book solutions is provided with great explanation. In this chapter we will solve long and short question answer.
Highlights
D. Answer the following questions in brief.
E. Answer the following questions.
A. Fill in the blanks.
1. About ___________ of water is present in oceans and seas.
2. Only 0.3 per cent of fresh water available for use is present in rivers, ___________ and ___________.
3. Ground water is drawn from wells, ___________ and ___________.
4. Use of ___________ and ___________ for irrigation reduces wastage of water.
5. The network of pipes which carries waste water to water treatment plant is called ___________.
Answer: (1) 97% (2) lakes, streams (3) tubewells, hand pumps (4) sprinkler, drip technique (5) 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 its solid form in glaciers and ice caps.
3. Farmers rely on ground water 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) False (2) True (3) True (4) False (5) True
C. Tick the correct option.
1. Ocean water is unfit for drinking as it is-
Answer: very salty
2. ‘Rain water harvesting’ can help us to conserve-
Answer: rain water
3. On the earth, the percentage of water, that is fresh and readily available for use, is, nearly-
Answer: 0.3%
4. One of the important factors, that can lead to a scarcity of water, is-
Answer: deforestation
5. “Waste water is also called-
Answer: sewage
D. Answer the following questions in brief.
1. Name the three forms in which water exists on the earth.
Answer: Ice (solid), Water (liquid) and water vapour (gas).
2. Give the meaning of the term ‘water table’.
Answer: The upper layer of groundwater is called water table.
3. Name two methods of drawing out ground water.
Answer: Two methods of drawing out ground water –
- Rehat or water wheel
- Stepwell/ tubewells
4. Name two activities which lead to the formation of sewage.
Answer: Washing clothes, Bathing etc.
5. State any two precautions that can help avoid the ‘choking of drains.
Answer: two precautions that can avoid choking of drains are –
- Do not throw solids, like left over food, leaves, cotton, polythene bags, etc., in the drains.
- Do not throw cooking oil, paints, chemicals, engine oil, in the drains.
E. Answer the following questions.
1. How is increase in population responsible for shortage of water?
Answer: Water is considered precious as it supports life on earth. With increase in population, demand for water has increased whereas its resources have depleted. This causes a shortage or scarcity of water.
2. Discuss, in brief, how ‘rain water harvesting’ can be done.
Answer: Rain water harvesting should be done by collecting rain water in underground tanks. This would help in replenishing the ground water.
3. Discuss any two causes that lead to a decrease in ground water level.
Answer: two causes that lead to a decrease in ground water level are:
- The amount of rainfall in most regions has decreased. This has happened due to many factors. Some of them are deforestation, increase in construction activity, etc.
- As the amount of rainfall decreases, farmers depend more on ground water for irrigation Hence, level of ground water is constantly decreasing.
4. How can ‘better management of water resources’ help in conservation of water?
Answer: Better management of water resources can help in conserving water. The rain water should not be allowed to flow into drains. Use of sprinklers and drip irrigation technique, for Irrigating the crops, can help in reducing wastage of water. Any broken, or leaking, pipe should be immediately repaired or replaced.
5. Write, in brief, about the basic details and the role of the ‘sewerage system’.
Answer: just as a network of pipes brings clean water to our homes, a network of pipes takes the waste water, or sewage, away. This network of pipes is called the sewerage system.
Role of the sewerage system
It carries the sewage, from its source, to a waste water treatment plant. The waste water is cleaned, and purified, by various processes at these treatment plants. The water, thus, treated and cleaned, is then allowed to mix with river or sea water.
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