NCERT solutions for Class 7 Science Waste water story

NCERT solutions for Class 7 Science Waste water story book solutions are available in PDF format for free download. These ncert book chapter wise questions and answers are very helpful for CBSE exam. CBSE recommends NCERT books and most of the questions in CBSE exam are asked from NCERT text books. Class 7 Science chapter wise NCERT solution for Science Book all the chapters can be downloaded from our website and myCBSEguide mobile app for free.

NCERT solutions for Science Waste water story Download as PDF

NCERT Class 7 Social Science Chapter wise Solutions

1. Nutrition in Plants
2. Nutrition in Animals
3. Fibre To Fabric
4. Heat
5. Acids Bases And Salts
6. Physical And Chemical Changes
7. Climate
8. Winds Storms And Cyclones
9. Soil
10. Respiration In Organisms
11. Transportation in Animals And Plants
12. Reproduction In Plants
13. Motion And Time
14. Electric Current And Its Effects
15. Light
16. Water
17. Forests: Our Lifeline
18. Waste Water Story

NCERT solutions for Class 7 Science Waste water story

Class–VII (CHAPTER-18)

WASTEWATER STORY

Question 1.Fill in the blanks:

(a)Cleaning of water is process of removing —————-.

(b)Wastewater released by houses is called ————.

(c)Dried ———- is used as manure.

(d)Drains get blocked by ————– and ————–.

Answer:

Fill in the blanks:

(a)Cleaning of water is process of removing contaminants.

(b)Wastewater released by houses is called sewage.

(c)Dried dung is used as manure.

(d)Drains get blocked by plastic and sludge.

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Question 2.What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer:

Sewage is wastewater released by homes, industries, hospitals, offices and other users. It includes rainwater that has run down the street during a storm or heavy rain. The untreated sewage may contain harmful chemicals that may kills the organisms growing in water. The sewage also contains nutrients that cause growth of algae and leads to scarcity of oxygen. That is why it is harmful to discharge untreated sewage into rivers or seas.

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NCERT solutions for Class 7 Science Waste water story

Question 3.Why should oils and fats be not released in the drain? Explain.

Answer:

Oil does not mix with water. Being lighter, oil floats on water. This prevents mixing of water and air. These reduce oxygen supply for aquatic plants and animals.

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NCERT solutions for Class 7 Science Waste water story

Question 4.Describe the steps involved in getting clarified water from wastewater.

Answer:

Treatment of wastewater involves physical, chemical and biological processes.

(a)Waste water is passed through bar screens to remove large objects like rags, sticks, cans, plastic packets, napkins etc.

(b)Water is passed to a grit and sand removal tank to allow sand, grit and pebbles to settle down.

(c)The water is then allowed to large settling tank to permit settling of solid faeces called sludge, which is removed using scarper.

(d)Air is pumped into the clarified water to help aerobic bacteria to grow and consume the wastes.

This type of water is discharged into rivers or ponds.

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Question 5.What is sludge? Explain how it is treated.

Answer:

Solid wastes faeces settle at the bottom and are removed with scrapper. This is sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water.

Sludge is transferred to a seperte tank where it is decomposed by the anaerobic bacteria. The biomass produced in the process can be used as fuel or can be used to produce electricity.

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NCERT solutions for Class 7 Science Waste water story

Question 6.Untreated human excreta is a health hazard. Explain.

Answer:

Untreated human excreta is a health hazard. It may cause water pollution and soil pollution. Both the surface water and ground water get polluted. Ground water is a source of water for wells, tube wells, springs etc. thus, it becomes the most common route for water borne disease. This includes cholera, typhoid, polio etc.

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Question 7.Name two chemicals used to disinfect water.

Answer:

Ozone, chlorine.

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NCERT solutions for Class 7 Science Waste water story

Question 8.Explain the function of bar screens in a wastewater treatment plant.

Answer:

Waste water is passed through bar screens. Large objects like rags, sticks, cans, plastics and napkins are removed.

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Question 9.Explain the relationship between sanitation and disease.

Answer:

Sanitation and disease are related to each other. To remain disease fee, we must observe sanitation. Clean environment is essential for preventing the growth of disease causing microbes. Dirty water around the living areas provides breeding ground for mosquito that are vectors of a number of disease. Sanitation prevents the growth of pathogens that cause disease.

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NCERT solutions for Class 7 Science Waste water story

Question 10.Outline your role as an active citizen in relation to sanitation.

Answer:

We all have a role to play in keeping our environment clean and healthy. We must realize our responsibility in maintaining the water sources in the healthy state. Adopting good sanitation practices should be our way of life. As an agent of change our individual initiative will make a great difference. We can influence others with our energy, ideas and optimism. A lot can be done if people work together. There is great power in collective action.

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Question 11.Here is a crossword puzzle: Good luck!

Across

3. Liquid waste products.

4. Solid waste extracted in sewage treatment.

6. A word related to hygiene

8. Waste matter discharged from human body.

Down

1. Used water.

2. A pipe carrying sewage.

5. Micro-organisms which causes cholera.

7. A chemical to disinfect water.

					1. W
					A					2. S
					3. S	E	W	A	G	E
					T					W
4. S	L	U	D	G	E		5. B			A
					W		A			R
					A		C
	6. S	A	N	I	T	A	T	I	7. O	N
					E		E		Z
					R		R		O
							I		N
	8. E	X	C	R	E	T	A		E

Answer:

					1. W
					A					2. S
					3. S	E	W	A	G	E
					T					W
4. S	L	U	D	G	E		5. B			A
					W		A			R
					A		C
	6. S	A	N	I	T	A	T	I	7. O	N
					E		E		Z
					R		R		O
							I		N
	8. E	X	C	R	E	T	A		E

NCERT solutions for Class 7 Science Waste water story

Question 12.Study the following statements about ozone:

(a)It is essential for breathing of living organisms.

(b)It is used to disinfect water.

(c)It absorbs ultraviolet rays.

(d)Its proportion in air is about 3%.

Which of these statements are correct?

(i) (a), (b) and (c)

(ii) (b) and (c)

(iii) (a) and (d)

(iv) All four.

Answer:

(ii) (b) and (c).

NCERT solutions for Class 7 Science

NCERT Solutions Class 7 Science PDF (Download) Free from myCBSEguide app and myCBSEguide website. Ncert solution class 7 Science includes text book solutions for CBSE Class 7 Science have total 18 chapters. 7 Science NCERT Solutions in PDF for free Download on our website. Ncert Science class 7 solutions PDF and Social Science ncert class 7 PDF solutions with latest modifications and as per the latest CBSE syllabus are only available in myCBSEguide.

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