1. Why do mountaineer carry oxygen cylinder while climbing?
Ans: This is because amount of oxygen at high altitude and become difficult to breadth.
2. Why does smell of perfumes reach us several meters away?
Ans: This is because air is continuously moving it takes the particle of perfumes along with it.
3. Why does crocodile keep it snout out of the water while resting?
Ans: Crocodile keeps it snout out of the water while resting to breathe through nostril.
4. Why do we see bubbles in water before it starts boiling?
Ans: This is because dissolved air is expelled out o heating.
5. Why do animals that live in holes or borrow in soil breadth?
Ans: They breadth in oxygen present between the soil partials.
6. What is the role of air in water cycle?
Ans: Air helps the water vapour to rise up to form cloud.
7. What does air bubbles coming out of soil, when pt in water indicates?
Ans: The presence of air
8. Why long chimneys are installed in factories?
Ans: To expel harmful smoke and gases away from our noses.
9. You have seen some tiny shining particles moving in the beam of sunlight. What are these particles?
Ans: Dust partials presents in air.
10. Why does the policeman wear a mask?
Ans: vehicles produce smoke, which is bad for health therefore to avoid breathing dust partials by covering face.
11. Why the transparent glass of windows, if not wiped off regularly, appears hazy?
Ans: Air contains some gases, water vapours and dust particles that stick to transparent glass of windows and it appears hazy.
12. Why during an incident of fire, one is advised to wrap a woolen blanket over a burning object.
Ans: Air presents in between the thread of woolen blanket form an insulating medium. It blocks supply of oxygen getting to the fire and the fire goes out.
13. How do plants and animals maintain the balance of oxygen and CO2 in the air?
Ans: Plants take carbon dioxide to prepare food and release oxygen during daytime. This oxygen is taken in by animals and carbon dioxide is released. Thus, plants and animals help in maintaining balance of oxygen
and carbon dioxide.
and carbon dioxide.
14. Why it advised to breathe through nose not through mouth?
Ans: This is because fine hair and mucus present inside the nose prevent dust particles from getting into the respiratory system.
15. Why earthworms come out of the soil, only during heavy rains?
Ans: when it rains heavily, water fills up all the spaces occupied by the air in the soil. Therefore earthworms have to come out for respiration.
16. Why all the oxygen of atmosphere does not get used up though a large number of organisms are consuming?
Ans: This is because the balance of oxygen and carbon dioxide in the atmosphere is maintained by plants and animals.
17. Why does a lump of cotton wool shrink in water?
Ans: A lump of cotton wool shrinks in water because water filled up the empty space that the air has occupied.
18. Why does air quality at every place to place is not good.
Ans: It is due to the smoke and gases emitted by the automobiles along with dust particles present in the air.
19. When tightly capped bottle full of water kept in the open sunlight, tiny bubbles were formed all around inside the bottle. Why so happened?
Ans: This is because air dissolved in water starts escaping in the form of tiny bubbles due to heat from the sun.
20. Explain reason why:
(a) A firki does not rotate in a closed area.
(b) The arrow of weather cock points towards a particular direction at a particular moment.
(c) An empty glass in fact is not empty.
Ans: (a) A firki does not rotate in a closed area due to lack of air movement.
(b) The arrow of weather cock points towards a particular direction at a particular moment because of the direction of the movement of wind.
(c)This is because everything is filled with air.
21 Fill in the blanks
(a) The ______ makes the windmill rotate.[Wind]
(b) Air is a ______ of some gases.[mixture]
(c) A weather cock shows the ______ in which the air is moving at that place. [Direction]
(d) Mountaineers carry oxygen ______ with them, while climbing high mountains [cylinder]
(e) The components of air which are harmful to living beings are ____ and ______. [Dust and smoke]
22. Write true /false
a. Atmosphere has only nitrogen.
b. Gases cannot dissolve in water.
c. Oxygen supports burning.
d. Air acts as a medium for flying.
e. At night plants let out oxygen.
f. Air is transparent.
Ans: (a) F (b) F (c) T (d). T (e). F (f) T