NCERT Solutions for Class 6 Science Chapter 15 Air Around us

NCERT Solutions for Class 6 Science Chapter 15 Air Around us are part of NCERT Solutions for Class 6 Science. Here we have given NCERT Solutions for Class 6 Science Chapter 15 Air Around us.

Board	CBSE
Textbook	NCERT
Class	Class 6
Subject	Science
Chapter	Chapter 15
Chapter Name	Air Around us
Number of Questions Solved	9
Category	NCERT Solutions

NCERT Solutions for Class 6 Science Chapter 15 Air Around us

NCERT TEXTBOOK EXERCISES
(Pages 153-154)

Question 1.
What is the composition of air?
Answer :
Various components of the air are:

• Nitrogen — 78.11%
• Oxygen — 20.95%
• Carbon dioxide — 0.03%
• Other gases
• Water vapours
• Dust particles

Question 2.
Which gas in the atmosphere is essential for respiration?
Answer :
Oxygen gas helps in the breakdown of the food to provide energy. This process is called respiration. Thus, oxygen helps in respiration.

Question 3.
How will you prove that air supports burning?
Answer :
To show that oxygen supports burning, we have to perform an activity as given below. Fix a candle about 6-8 cm long in the centre of a trough or a plate having a raised rim. Now fill the trough or a plate with water to more than half of its height. Light the candle. Next, take a one litre plastic water bottle and with the help of sharp knife remove its base. It will serve the purpose of a vessel. Tighten its cap. Then place it over the candle as shown in Fig. 15.5. Observe carefully what happens to the burning candle and the water level. Light the candle again and perform this experiment with a two-litre plastic water bottle. Next, make several holes all over the surface of smaller plastic bottle with the help of a hot screwdriver or nail. And repeat the experiment with this water bottle.

The candle flickers out after some time in the first two conditions. The candle burns for a shorter period in the smaller bottle. We kept the air limited in the first two conditions. However, in the third experimental condition (b), air was allowed to come and go through the vessel. Candle burns continuously in the bottle having holes. We also see that, if not covered in any closed space, a candle continues burning till it is completely finished. This reflects that burning cannot take place without a continuous supply of air. We can conclude that air is necessary for burning things.

In the first two conditions, there was a rise in water level, while no rising of water would have been observed in the third set up. This indicates that, during burning, some amount of air was used up. The component of air that supports burning is called oxygen.

Question 4.
How will you show that air is dissolved in water?
Answer :
To show that air is dissolved in water, we have to perform following activity: Take some water in glass vessel or beaker. Heat it slowly on tripod. Look carefully at the inner surface of vessel (See Fig. 15.6).
We see that tiny air bubbles are sticking on it.
These air bubbles are mainly of oxygen gas present in air, which is dissolved in water. When we heat up water, air dissolved in it escapes out in the form of bubbles.

Question 5.
Why does a lump of cotton wool shrink in water?
Answer :
In a cotton lump, a large amount of air is trapped between thin and light cotton fibres making it fluffy. When these fluffy lumps come in contact with water they shrink because the fibres get weight after wetting and the air escapes out from it.

Question 6.
The layer of air around the earth is known as …………………….. .
Answer :
Atmosphere.

Question 7.
The component of air used by green plants to make their food, is …………………………… .
Answer :
CO₂ (Carbon dioxide).

Question 8.
List five activities that are possible due to the presence of air.
Answer :
Air is very important for living beings. Its various activities are listed below:

1. It helps in burning.
2. It is essential for the respiration in living being.
3. It is helpful in movements of sailing yachts, gliders, parachutes and air crafts.
4. Air current makes the windmill to rotate. The windmill is used to draw water from tube wells and to run flour mills. Windmill also generates electricity.
5. Birds, bats and insects fly in air.
6. Air also helps in the dispersal of seeds and pollens of flowers of several plants.
7. Compressed air is used in tyres in vehicles.
8. Nitrogen present in the air is used on a large scale to manufacture fertilizers.
9. Helps in winnowing.
10. Helps in hearing sounds.
11. CO₂ present in air is used by plants in making food (photosynthesis).
12. Activities like cloud formation, thundering, etc. occur in air.

Question 9.
How do plants and animals help each other in the exchange of gases in the atmosphere?
Answer :
The carbon dioxide along with water is used by green plants in the presence of sunlight. Oxygen is produced along with food during photosynthesis. Plants also consume oxygen for respiration, but they produce more of it than they consume. That is why we say plants produce oxygen.

Since plants produce oxygen, while animals consume it, thus it is obvious that animals cannot live without plants, since plants are their food. Moreover, plants could not survive for long without animals. They would consume all the carbon dioxide in the atmosphere. We can see that both need each other, as the balance of oxygen and carbon dioxide in the atmosphere is thus maintained. This is because of the interdependence of plants and animals on each other.

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