Page 163 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

4. Give two uses of biogas.

Ans: (a) It is used as a domestic fuel.
(b) It is used to generate electricity.

5. Who designed vacuum toilet system used in aeroplanes?
Ans: James Kemper

6. Name diseases that are spread by mosquitoes.
Ans: Malaria & Dengue.

7. Name a few water-borne diseases.
Ans: Diarrhoea, Dysentry, Typhoid fever, etc.

8. Name the organic impurities present in sewage.
Ans: Animal & human waste, oil, waste from food herbicides, etc.

9. What leads to soil contamination?
Ans: Soil gets contaminated when toxic chemical waste from industries or agricultural

fields seeps into the soil and alters its chemical nature.
10. Name the chemical used to kill germs present in water to make it fit for drinking.

Ans: Chlorine
E. Short-answer questions.

1. Why should we not throw the following into drains?
(a) Oil and grease

(b) Chemicals, such as paints and cleaning liquids
Ans: Oil and other greasy material should not be thrown down the drain. The oil clogs

the pores in the soil and makes infiltration of water difficult. Paints, medicines
and insecticides should not be put into drains as they kill the water-purifying

microorganisms.
2. What is the importance of sewage treatment?

Ans: Sewage treatment is important because it keeps our environment clean & healthy.
It removes harmful substances & germs from wastewater, preventing pollution in

rivers, lakes & oceans. This protects plants, animals & people from diseases. Treated
water can also be reused for farming & other purposes, which helps save water.

3. How does dumping of sewage in water bodies harm the marine life?
Ans: When sewage is dumped into water bodies, it not only pollutes them but also

contaminates the groundwater which is consumed in households, causing diseases,
such as cholera, diarrhoea and typhoid.

4. What is eutrophication?
Ans: Eutrophication is the enrichment of nutrients in water bodies that promotes excess

growth of plant life.

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