Class 8 Social Science Chapter 12 Water on Earth - Questions and Answers

Study Notes for Class 8th Social Science ഭൂമിയിലെ ജലം | Text Books Solution Social Science (English Medium): Chapter 12 Water on Earth

Class 8 Social Science - Questions and Answers: Chapter 12: Water on Earth
Water on Earth - Questions and Answers
1. On which day do we celebrate World Water Day?
Answer: March 22nd
 
2. Which is the only living planet in the solar system?
Answer: Earth

3. Earth is also known as a watery planet. Why?
Answer: Three-fourths of the earth's surface is covered with water.  71 per cent of the earth's surface is covered with water.

4. List out any five sources of water.
Answer:
• Oceans
• Springs
• Wells
• Ponds
• Rivers

5. Which type of water can be seen more on earth- freshwater or saline water?
Answer:  Saline water

6. What is the percentage of saline water to the total water on earth?
Answer: 97%

7. How much percentage of freshwater is available for humans?
Answer: 3%

8. Define the Water cycle.
Answer: The cycle of processes by which water circulates between the earth's oceans, land and atmosphere involving precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation and transpiration

9. How can we classify sources of water? Give examples.
Answer:
• Surface water and Groundwater.
• Surface water: Oceans, rivers, lakes and backwaters
• Groundwater: Wells, ponds, tube wells

10. What is porosity? Write an example for a porous material.
Answer:
• Porosity is the term for the porous state.
• Eg: Clay

11. What do you mean by permeability?
Answer: Water will be available only at places where the pores in the rocks are interconnected. This is due to the fact that water can move through these pores. This quality of rocks is known as permeability.

12. What is the reason for the accumulation of water in paddy fields?
Answer: In paddy fields, we can see the presence of clay. It has high porosity but low permeability. This means that clay will not permit water to pass through it.

13. What do you mean by ' water table'?
Answer: The surface of the water-rich part beneath the ground is known as the ' water table'.

14. Define the term 'underground water'.
Answer: The water stored beneath the ground is the 'underground water'.

15. What are aquifers?
Answer: Water that percolates through the topsoil will be collected in the pore spaces of the soil and gaps in the rocks. Such storage spaces are called aquifers.

16. The water table rises during the rainy season and lowers during summer. Why is it so?
Answer: Water table rises during rainy season due to recharge received from rainfall and falls back during the summer season due to lack of recharge

17. In which situations tube wells are ideal?
Answer: It is difficult to dig wells where the water table is deep. Tube wells are ideal in such situations.

18. In sandy regions which type of wells is used?
Answer: Filter point wells - shallow tube wells dug in sandy regions.

19. What are artesian wells?
Answer: If there be a permeable rock layer in between two impermeable rock layers. Water will rise to the surface automatically due to pressure if we dig into this permeable rock layer. Such wells are known as artesian wells.

20. Explain spring and hot spring.
Answer: Water will be flowing out along the surface wherever the water table touches the ground. This is known as "spring".
At some places, such water flows are characterised by hot water. These are known as hot springs.

21. What is geysers? Write an example.
Answer: The phenomenon of severe ejection of water from within the earth at regular intervals is known as "geysers".
Example - The Old Faithful geyser of the Yellow Stone National Park in U.S.A.

22. Write the reason for the formation of hot springs and geysers. 
Answer: This is due to the fact that water can move through these pores. This quality of rocks is known as permeability. The water that seeps through the fissures on the earth comes in contact with the magma and leads to the formation of hot springs and geysers.

23. Write short note on Wetlands
Answer: Wetlands are natural sinks of surface water. Paddy fields, ponds, swampy regions and all low lying regions come under the category of low lands. The water stored here form part of the groundwater.

24. Reclamation of the wetlands lead to several environmental problems. Write any two
Answer:
• Lowering of water level in wells.
• Floods become common in rivers even in slight rains.

25. On which day do we celebrate World Watershed Day?
Answer: February 2nd

26. List out the uses of water.
Answer:
• For drinking. 
• For cleaning dishes. 
• For cooking. 
• for watering plants. 
• for washing clothes. 
• for bathing. 
• for generation of hydroelectricity. 

27. Point out the threats to water resources. 
Answer:
• Even the available freshwater sources are on the verge of depletion 
• Increase in the consumption of water has also influenced the availability of water. 
• Water pollution 

28. Identify any five situations that lead to water pollution. 
Answer:
• The waste from households, factories, or agricultural land gets discharged into rivers or lakes 
• Dumping 
• Oil pollution 
• Acid rain 
• Industrial waste 

29. What is water pollution?
Answer: The undesirable change in the physical, chemical and biological properties of water is termed water pollution.

30. Name the law that enforces the control of water pollution in our country.
Answer: The law on prevention and control of water pollution.

31. What are the effects of water pollution?
Answer: 
• Water pollution not only affects the availability of freshwater but leads to the pollution of land and air as well.
• The survival of plants and animals are put in danger.

32. What can be done by individuals and society to check water pollution?
Answer:
• Reduce the use of herbicides, pesticides, and fertilizers.
• Do not dump waste near public taps, wells or other water sources
• Proper sewage treatment and management.
• Protect fields and wetlands.
• Always opt for recyclable and reusable options
• Skip the use of plastics
• Practice organic farming

33. List out the natural means to sink water into the soil. 
Answer: Forests, ponds, wetlands, sacred groves etc.

34. Write a short note about the importance of the conservation of water. 
Answer: Nature provides enough water for us. We can solve the issues of water scarcity and drought if we make use of the rainwater effectively. Allowing each drop of rainwater to percolate at the place where it falls is the basic principle in water conservation. Harvesting rainwater is the best way to solve the problem of water scarcity. 

35. What are the different types of rainwater harvesting? 
Answer:
a) Rooftop rainwater harvesting: The level of the underground water can be raised either by draining the rainwater to the ground or by collecting it in storage tanks. 
b) Surface run-off harvesting: Includes all systems that collect and conserve surface run-off after a rainstorm or in intermittent streams, rivers, or wetlands for storage in open ponds and reservoirs 

36. List out the activities which help in collecting and storing the rainwater in the soil. 
Answer:
• Conservation of wetlands 
• Protection of forests 
• Terrace farming 
• Mulching 
• Construction of check dams 
• Construction of mud walls 
• Digging rainwater percolation pits 

37. Write a note on the recycling of water. 
Answer: It is the process of converting wastewater into water that can be reused for other purposes. Reuse may include irrigation of gardens and agricultural fields. Recycling water also prevents pollution by decreasing the amount of wastewater that must be discharged. When water is used for agricultural irrigation, the nutrients (nitrogen, phosphorus) in the treated wastewater act as a fertilizer.

38. Water drained from the kitchen can be used for watering vegetables raised in the courtyard. List out its merits.
Answer:
 • Can avoid using drinking water for other purposes.
• Excessive use of water can be reduced.
• Decreasing the amount of wastewater that must be discharged
• When water is used for agricultural irrigation, the nutrients (nitrogen, phosphorus) in the treated wastewater act as a fertilizer.

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