DAV Class 7 Science Chapter 16 Water Question Answer Notes
DAV Class 7 Science Chapter 16 Water Question Answer Notes Solution by Expert Science Teacher. DAV Class 7 Science 16th Chapter Water for Students of DAV Schools.
Lesson No 16
Water
A.) Fill in the blanks
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.
Answer: (1) False, only 3% of water is freshwater (2) True (3) True (4) False, it decreases groundwater level (5) True
C.) Tick the correct option.
Go beyond traditional BBA College with NEXIS 3-year UG
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 which is solid , Water which is liquid and water vapour that is a gas.
2.) Give the meaning of the term ‘water table’.
Answer: The upper most layer of groundwater is called the water table.
3.) Name two methods of drawing out ground water.
Answer: Two methods of drawing out ground water are as follows- through wells, through water pumps
4.) Name two activities which lead to the formation of sewage.
Answer: washing clothes in waterbodies, bathing in them..
5.) State any two precautions that can help avoid the ‘choking of drains.
Answer: two precautions that can avoid choking of drains are –
- Not throwing solid wastes especially plastic bags
- By not throwing chemicals and oils , also not letthing weeds grow within them.
E.) Answer the following questions.
1.) How is increase in population responsible for shortage of water?
As the population grows, so does the need for water. Because there is more demand than there is supply, there could be a water shortage. Water sources could also become less useful as a result of contamination as the population expands. A region’s ability to store rainwater and replenish aquifers declines when more people move there because they have a tendency to occupy more area.
2.) Discuss, in brief, how ‘rain water harvesting’ can be done.
Rainwater harvesting is a method for collecting and preserving rainwater for later use. Rainwater can be captured from rooftops and other surfaces that collect it in order to accomplish this and stored into buckets, storage tanks, or other sites for later use. Another option for subsurface storage is to employ infiltration water wells or groundwater recharge systems. Rainwater collecting has a variety of applications, including for domestic usage, agriculture, and animal protection. Around the world, people collect rainwater, which might be a significant supply of water for houses and communities.
3.) Discuss any two causes that lead to a decrease in ground water level.
1.) Over-Exploitation: The excessive extraction of groundwater for industrial, agricultural and domestic purposes leads to a decrease in the water table. This occurs when extraction exceeds the rate of replenishment, leading to a decrease in the groundwater levels.
2.) Climate Change: Climate change has led to an increase in the frequency and intensity of droughts, resulting in lowered groundwater levels. This occurs as a result of reduced precipitation, higher temperatures, and increased evaporation.
4.) How can ‘better management of water resources’ help in conservation of water?
By lowering water waste and increasing water consumption effectiveness, effective groundwater recharge management can support water conservation. This can be achieved by putting in water-saving fixtures, collecting as well as using rainwater, and employing other water-saving techniques. Additionally, improved management of water resources may help identify and lessen water contamination, protecting and conserving the current water supplies.
5.) Write, in brief, about the basic details and the role of the ‘sewerage system’.
The sewerage system is a network of pipes, valves, as well as treatment centers used to collect and remove wastewater from houses and businesses. The system that gathers wastewater from faucets, restrooms, as well as other sources, transports it to a treatment center, processes it as needed, and then appropriately disposes of it. Because it removes contaminants from water sources, lowers the frequency of diseases spread by polluted water, and guards against water contamination, the sewage system is essential for maintaining public health.
More Extra Questions for Preparation
Q.1.) Fill in the blanks.
1.) About 97 % of all the water on earth is present in oceans and seas.
2.) Cholera disease is caused by contaminated water.
3.) Sprinklers and drip irrigation helps in reducing wastage of water in rain water harvesting.
4.) Water bodies on earth receive water mainly from rainfall.
5.) Water occurs in frozen form on polar ice caps and glaciers.
Q.2.) True or false.
1.) Only 0.3% of fresh water is present in rivers, lakes and streams.
Answer – True
2.) The upper layer of water is called ground water.
Answer – False
3.) The water below the layer is called water table.
Answer – False
4.) The waste water flows through a network of underground drains.
Answer – True
Q.3.) MCQ’S.
1.) Water in its form is available in oceans.
a.) Solid
b.) Liquid
c.) Gases
d.) None of these
Answer – b.) Liquid
2.) Only % of fresh water is present.
a.) 8%
b.)10%
c.)15%
d.) 3%
Answer – 3%
3.) will cause an increase in the level of carbon dioxide gas in the atmosphere.
a.) Planting of trees
b.) Cutting of trees
c.) Watering of plants
d.) Both a and b
Answer – b.) cutting of trees
4.) Due to increase in population, the demand for usable water has .
a.) Decreased
b.) Increased
c.) No change
d.) None of these
Answer – b.) Increased
5.) The top level of the ground water is called
a.) Ground level
b.) Sea level
c.) River level
d.) Water table
Answer – d.) Water table
Q.4.) Define the following.
1.) Ground water.
Answer – The water below this layer is known as ground water.
2.) Sewage.
Answer – Waste water is produced in offices, hospitals and factories. This waste water is called sewage.
3.) Waste water.
Answer – Water used for daily needs, produces a lot of water which is dirty and contains many impurities. Such water is called waste water.
Q.5.) Answer the following questions.
1.) Explain rain water harvesting.
Answer – Rain Water Harvesting-
Rain water should be collected in underground tanks and allowed to seep through the soil. This will
replenish the ground water. Rain water can also be collected in open tanks and used for daily needs.
This is called rain water harvesting.
2.) How we can maintain water to be polluted and maintain a clean surrounding?
Answer – Water can be maintained by some following rules given below:-
a.) Reduce the quantity of waste water being produced in our homes.
b.) Do not throw solids, like leftover food, leaves, cotton, polythene bags, etc.
c.) Do not throw cooking oil in the drain.
d.) Do not throw chemicals, like paints, medicines, engine oil, etc., in the drain. These chemicals kill the (friendly) micro-organisms, present in the sewage, which help to purify water.
3.) What does contaminated water causes?
Answer– Contaminated drinking water can cause diseases like cholera, typhoid, jaundice, etc.
4.) How we can save water?
Answer – We should save water by following –
a.) Turn off the tap while brushing teeth.
b.) Get the leaking taps repaired immediately.
c.) water the plants with a mug instead of a pipe.
5.) What is green house effect?
Answer –
a.) Carbon dioxide gas, breathed out by humans and animals, is used up by the plants to prepare their own food through the process of photosynthesis.
b.) Unnecessary, cutting of trees will cause an increase in the level of carbon dioxide gas in the atmosphere.
c.) This gas helps in trapping a part of the energy of sun rays in the earth’s atmosphere by not allowing that energy to escape.
d.) This causes an increase in temperature on the surface of earth. This phenomenon is called Green House Effect’.
6.) What are the reasons of shortage of water?
Answer – The major reasons of shortage of water are given below:
a.) Water bodies on earth receive water mainly from rainfall. The amount of rainfall in most regions has decreased. This has happened due to many factors.
b.) Some of them are deforestation, increase in construction activity, increase in number of vehicles and industries. As the amount of rainfall decreases, farmers depend more on ground water for
irrigation.
c.) Hence, level of ground water is constantly decreasing.
d.) With increase in population, demand for water has increased whereas its resources have depleted. This causes a shortage or scarcity of water.