NCERT Exemplar Solutions: Air around Us | Science Class 6 PDF Download

Ans: (d)
Air is omnipresent in nature and is present everywhere including soil. This can be proved by a simple activity.
By taking a lump of dry soil in a beaker or a glass, add water to the soil, we can see that the soil has absorbed the water in the form of bubbles.

Ans: (c)
Wind does not help in the movement of ceiling fan since ceiling fan moves by electricity.

Ans: (d)
Air plays a major role in the water cycle. Water vapours are risen up to form clouds.

Ans: (b)
As higher we go, the atmosphere gets thinner and the supply of oxygen is reduced. This makes difficulty in breathing on hill stations and mountains. Therefore, while climbing high mountains, mountaineers carry oxygen cylinders with them.

Ans: (a)
Bubbles of air came out from the bottle. Some water entered the bottle.

Ans: (a)
The atmosphere contains nitrogen in the largest amount. It mainly constitutes 78% of nitrogen, 21% of oxygen and the remaining 1% is formed by carbon dioxide, water vapour, few other gases and dust particles.

Ans: (c)
Water vapour is important for the water cycle in nature.
Nitrogen is necessary for plants.
Carbon dioxide is essential for photosynthesis.
Hence, dust particles and smoke coming out of factories are very harmful to living beings.

Ans: (c)
 When the water is poured on the lump of soil, the soil absorbs the water in the form of bubbles.

(a) True
(b) True
(c) False – Air helps in the movement of sailing yachts and gliders and also helps in the flight of birds and aeroplanes.
(d) False – Air does occupy space.

Air plays an important role in a number of musical instruments such as mouth organ, harmonium, shehnai, trumpet, trumpet and flute.

Here are the arranged words:

(a) 99% of the air is made up of Oxygen and nitrogen together.
(b) Aquatic animals use dissolved air for respiration.
(c) The air in motion is called wind.

(a) wind
(b) mixture
(c) direction
(d) cylinders

(a) The policeman has worn a mask to cover his nose and mouth.
(b) He has put a mask on his nose to protect himself from dirt and polluted air. Since the mask avoids exposure to the harmful exhaust of vehicles, thus prevents the harmful gases and dust particles entering our body.
(c) In the given figure the quality of air is bad since it is polluted. Due to the smoke and harmful gases such as carbon monoxide and sulphur dioxide emitted by the automobiles along with dust particles the air is polluted.

When the air gets dissolved in water it escapes in the form of tiny bubbles due to heat from the sun. Hence, tiny bubbles were formed all around inside the bottle.

Here is the correct match:

(a) In a closed area, there is a lack of air movement which does not support the rotation of a firki. A firki usually rotates when placed in an open area due to the moving air present all around.
(b) A weathercock is an instrument used to indicate the direction of the wind. It consists of an arrow, mounted at its centre of gravity for it to move freely about a vertical axis. Hence, the arrow points towards a particular direction at a particular moment to show the latest direction of the wind movement.
(c) An empty glass is not empty it is filled with air. It can be proved with a simple experiment in which an empty bottle is turned upside down in a beaker filled with water. The water does not enter the bottle when it is pushed in an inverted position because there is no space for air to escape. When the bottle is tilted, the air is able to escape out in the form of bubbles and water fills up the empty space. This shows that even an empty glass is filled with the air.
(d) Yes, breathing through the mouth may harm us. Some gases, water vapour and dust particles may be present in the air. When we inhale air through nostrils, the fine hair and mucus present in the nose prevent the dust particles from entering the respiratory tract. But, if we breathe through the mouth, the harmful dust particles may enter our body and make us ill. Thus, breathing through the mouth may harm us.

(a) If oxygen gas disappears from the atmosphere, life becomes impossible on earth since oxygen is very essential for the survival of the living organisms. Animals and plants take in oxygen from the atmosphere and release carbon dioxide during respiration. It becomes impossible for living organisms to breathe in the absence of oxygen and hence, eventually, the organisms will die so oxygen is very necessary.
(b) Nitrogen constitutes a major part of the atmosphere and it does not support burning. If nitrogen gas disappears from the atmosphere, things on earth will burn very fast which may produce disastrous results. Plants require nitrogen for their growth, although it does not absorb nitrogen directly from the air. They consume it in the soluble form either through fertilizers which can be absorbed through the soil. Hence, nitrogen is very important for plants, animals, humans and other organisms to grow properly.
(c) Plants require carbon dioxide to manufacture their own food by the process of photosynthesis. If carbon dioxide disappears from the atmosphere, the plants will not be able to produce their food and oxygen will not be released by them which will disturb the carbon dioxide – oxygen ratio in the atmosphere. Hence, in the absence of oxygen and food, there will be no life on earth.

(a) The tiny bubbles appeared before the water started to boil since the air dissolved in water. Once the water started to boil, the air dissolved in water escaped in the form of bubbles.
(b) Paheli had boiled the water completely where the air from the water had escaped out, so on reheating the cooled boiled water will not make any tiny bubbles as there is no air present in it.

The dull appearance of the leaves and flowers of the roadside plants may be due to the air quality present in the open area which includes dust particles emitted from the vehicles, chimneys and factories. These dust particles stick to the plant parts which made them appear dull.