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CBSE Worksheet-59

Class – VII Science (Waste-water Story)

1. Liquid waste from houses is called

a. Sewage

b. Sludge

c. Smog

d. Effluent

2. Biodegradable waste

a. Decomposes in nature by microbes

b. Does not decompose

c. Enters the food chains then causes bio magnification

d. Accumulates in environment

3. Polythene and plastics

a. Degrade in the environment very easily

b. Are not harmful

c. Do not generate any bad odour

d. Are non-biodegradable and very harmful

4. Which of the following is non-biodegradable waste?

a. Vegetable and fruit peels.

b. Plants and animals excreta

c. Plastic

d. Cotton cloths

5. Match the following

Column A Column B

a. Polythene i. Waste water from homes and industries

b. Fruits peel ii. Chlorination

c. Sewer system iii. Biodegradable

d. Sewage iv. Network of drainage pipe to carry sewage

e. Disinfection v. Non-biodegradable

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6. Fill in the blanks with suitable words

a. After treatment the sewage is discharged into a -----------------.

b. The ------------------ system transport the sewage from homes to treatment

plant.

c. Last stage in treatment of sewage is --------------------.

d. Open drains cause -------------- conditions.

e. Solid parts of sewage can be used as ------------------.

7. What is meant by sewage? What does it mainly consists of?

8. Mention some importance of drainage system.

9. Write difference between biodegradable and non-biodegradable wastes.

10. Solve the cross word puzzle.

Across

2. Useless things produced.

4. Chemicals used for killing germs.

Down

1. Waste water from homes and industries.

3. Disease causing microorganisms.

5. Non-biodegradable solid waste

1.S

5.P

2.W

3.G

4.C

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Answer key

1. a

2. a

3. d

4. c

5. (a) – (v), (b) – (iii), (c) – (iv), (d) – (i), (e) – (iv).

6. (a) Water bodies (b) sewer system (c) chlorination (d) unhygienic (e) fertilizers.

7. Sewage is the waste water from homes and industries. It consists of human excreta,

dirt, and food particles etc.

8. Drainage system is an absolute necessity for safe disposal of sewage. In absence of an

efficient system of sewage the sanitation of a place may suffer. It may cause water

borne disease.

9. Biodegradable wastes are organic wastes which are decomposed by bacteria and

other microorganisms into simpler components. Non biodegradable are mostly

inorganic and can not be converted into simpler forms.

10.

1.S

E 5.P

2.W A S T E L

A A

G 3.G S

E E T

4.C H L O R I N T I O N

M C

S