Page 88 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

5. When we exhale out air in freshly prepared lime water, it turns milky.

Ans. It happens because the carbon dioxide in our breath reacts with the calcium hydroxide

in the lime water. This reaction forms calcium carbonate which is insoluble in water
& appears as milky.

E. Very short-answer questions.
1. Give the name of respiratory organs for the following.

(a) Fish

Ans. Gills
(b) Human being

Ans. Lungs
(c) Cockroach

Ans. Spiracles & tracheae.

2. What happens to the breathing rate when you:
(a) exercise

Ans. It increases.

(b) sleep
Ans. It decreases.

3. Write the principle of the process of fermentation.

Ans. Fermentation is the anaerobic conversion of sugars into alcohol or acids by
microorganisms like yeast or bacteria.

4. Name the chemical used to check the presence of carbon dioxide in exhaled air.
Ans. Lime water (calcium hydroxide)

5. What is the other name for windpipe?

Ans. Trachea
6. What is the function of hair in the nostrils?

Ans. The tiny hair in the nostrils filter out dust and other foreign particles present in the
air.

7. What is the name of the wall which divides our nasal cavity?

Ans. Central septum
F. Short-answer questions.

1. Sometimes we see that farmers loosen the soil. Give reason.

Ans. Farmers often till the soil to create air spaces in soil so that the roots may breathe
properly. It also helps them to penetrate easily through the soil and absorb water

and minerals.

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