NCERT Exemplar Problems Class 6 Science – Air Around Us

Question 1:
Which of the following statements is incorrect?
(a) All living things require air to breathe
(b) We can feel air but we cannot see it
(c) Moving air makes it possible to fly a kite
(d) Air is present everywhere but not in soil
Solution:
(d) Air is present everywhere even in the soil. Oxygen is trapped in the soil and is helpful for organisms present in the soil for breathing
Note: The animals which live in soil and the plant roots which grow in soil need oxygen to breathe.

Question 2:
Wind does not help in the movement of which of the following?
(a) Firki (b) Weather cock
(c) Ceiling fan (d) Sailing yacht
Solution:
(c) Wind does not help in movement of ceiling fan. It rotates by electricity.

Question 3:
What is not true about air?
(a) It makes the windmill rotate
(b) It helps in the movement of aeroplanes
(c) Birds can fly due to presence of air
(d) It has no role in water cycle
Solution:
(d) The presence of water vapour in air is important for the working of water cycle in nature (This is because it is water vapour present in air which rises high in the sky along with hot air, gets cooled, condenses to form clouds and then brings rain on the earth).

Question 4:
Mountaineers carry oxygen cylinders with them because
(a) there is no oxygen on high mountains
(b) there is deficiency of oxygen on mountains at higher altitude
(c) oxygen is used for cooking
(d) oxygen keeps them warm at low temperature
Solution:
(b) As we go up above the sea level, the atmospheric pressure goes on decreasing and the amount of oxygen also decreases at higher altitude. This is why, mountaineers carry oxygen, cylinders with them.

Question 5:
Boojho took an empty plastic bottle, turned it upside down and dipped its open mouth into a bucket filled with water. He then tilted the bottle slightly and made the following observations:
(i) Bubbles of air came out from the bottle.
(ii) Some water entered into the bottle.
(iii) Nitrogen gas came out in the form of bubbles and oxygen gas dissolved in water.
(iv) No bubbles formed, only water entered into the bottle.
Which observation(s) is/are correct?
(a) (i) and (ii) (b) Only (iv)
(c) (iii) and (iv) (d) Only (i)
Solution:
(a) Bubbles of air came out from the bottle and some water entered into the bottle, when it was tilted.

Question 6:
Which of the following components of air is present in the largest amount in the atmosphere?
(a) Nitrogen (b) Oxygen
(c) Water vapour (d) Carbon dioxide
Solution:
(a) Nitrogen is present in the largest amount in the atmosphere. It occupies 78.09% of atmosphere.

Question 7:
The components of air which are harmful to living beings are
(a) nitrogen and carbon dioxide
(b) dust and water vapour
(c) dust and smoke
(d) smoke and water vapour
Solution:
(c) Dust and smoke present in air are harmful to living beings.
Note: Breathing in air containing smoke and dust may enter our respiratory system (lungs, etc.) and damage our health.

Question 8:
Usha took a lump of dry soil in a glass and added water to it till it was completely immersed. She observed bubbles coming out. The bubbles contain
(a) water vapour
(b) only oxygen gas
(c) air
(d) None of the above
Solution:
(c) The bubbles contain air because soil absorbs some amount of air. The air is present in the spaces between the soil particles.

Very Short Answer Type Questions

Question 9:
State whether the following statements are true or false. If false, correct them.
(a) Plants consume oxygen for respiration.
(b) Plants produce oxygen during the process of making their own food.
(c) Air helps in the movements of sailing yachts and glider but plays no role in the flight of birds and aeroplanes.
(d) Air does not occupy any space.
Solution:
(a) True (b) True
(c) False, air also helps in the flight of birds and aeroplanes.
(d) False, air occupies space, i.e. Air fills all the space available to it.

Question 10:
In a number of musical instruments, air plays an important role. Can you name some such instruments?
Solution:
Air plays an important role in number of musical instruments such as flute, trumpet, harmonium, shahnai.

Question 11:
In the boxes of Column I, the letters of some words got jumbled. Arrange them in proper form in the boxes given in Column II.

Solution:
(a) Windmill (b) Oxygen
(c) Smoke (d) Dust

Question 12:
Make sentences using the given set of words.
(a) 99%, oxygen, nitrogen, air, together
(b) Respiration, dissolved, animals, air, aquatic
(c) Air, wind, motion, called
Solution:
The correct sentences are :
(a) Oxygen and nitrogen together make up 99% of the air.
(b) Aquatic animals use dissolved air for respiration.
(c) Air in motion is called wind.

Short Answer Type Questions

Question 13:
A list of words is given in a box. Use appropriate words to fill up the blanks in the following statements.
Air, oxygen, wind, water, vapour, mixture, combination, direction, road, bottles, cylinders.
(a) The ………. makes the windmill rotate.
(b) Air is a ………. of some gases.
(c) A weather cock shows the ……….. in which the air is moving at that place.
(d) Mountaineers carry oxygen ………… with them, while climbing high mountain.
Solution:
(a) wind (b) mixture
(c) direction (d) cylinders

Question 14:
Observe the given figure carefully and answer the following questions:

(a) What is covering the nose and mouth of the policeman?
(b) Why is he putting a cover on his nose?
(c) Can you comment on air quality of the place as shown in the figure?
Solution:
(a) Mask is covering the nose and mouth of the policeman.
(b) Policeman is putting a cover on his nose to save himself from dirt/polluted air.
(c) Air quality of the place is not good. It is due to the smoke and gases emitted by the automobiles along with dust particles present in the air.

Question 15:
Garima observed that when she left her tightly capped bottle full of water in the open sunlight, tiny bubbles were formed all around inside the bottle. Help Garima to know why it so happened?
Solution:
Air is dissolved in water in the form of oxygen. When water bottle is left in the open sunlight, tiny bubbles were formed all around inside the bottle because air dissolved in water starts escaping in the form of tiny bubbles due to heat from the sun.

Question 16:
Match the Column I with Column II.

Solution:
The correct matching is as given:
(a)-(iv), (b)-(iii), (c)-(v), (d)-(i), (e)-(ii)

Long Answer Type Questions

Question 17:
Explain the following observations briefly.
(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.
(d) Breathing through mouth may harm you.
Solution:
(a) Motion of firki is based on the pressure/force applied by air on the blades of the firki. A firki does not rotate in a closed area because of lack of air movement.
(b) The arrow of weather cock points towards a particular direction as it shows the direction in which the air is moving at that place at a particular moment.
(c) An empty glass in fact is not empty. It is filled with air. Air is present everywhere.
(d) Breathing through mouth may harm us because we may inhale dust if present in air which may enter our respiratory system (lungs, etc.) and damage out health.

Question 18:
Write a few sentences for an imaginary situation if any of the following gases disappear from the atmosphere.
(a) Oxygen
(b) Nitrogen
(c) Carbon dioxide
Solution:
(a) There will be no life on the earth. Oxygen is vital for life. It helps in burning, respiration, photosynthesis, etc. Oxygen is basic need of all living beings.
(b) Nitrogen does not support burning. If nitrogen gas disappear from the atmosphere, things will burn very fast.
(c) Carbon dioxide is needed for photosynthesis which occurs in green plants. In its absence, plants will not be able to prepare their food and hence, without carbon
dioxide there would be no plants or animals on the earth.

Question 19:
Paheli kept some water in a beaker for heating. She observed that tiny
bubbles appeared before the water started to boil. She boiled the water for about 5 min and filled it in a bottle upto the brim and kept the bottle airtight till cooled down to room temperature.
(a) Why did the tiny bubbles appeared?
(b) Do you think tiny bubbles will appear on heating the water taken out
from the bottle? Justify your answer.
Solution:
(a) Air is dissolved in water in the form of oxygen. Tiny bubbles are formed, when air present in the water escape on boiling it.
So, tiny bubbles appeared due to the evolution of air dissolved in water.
(b) No, tiny bubbles will not appear as there is no dissolved air in this water.

Question 20:
On a Sunday morning, Paheli’s friend visited her home. She wanted to see some flowering plants in the nearby garden. Both of them went to the garden. While returning from the garden, they also observed some flowering plants on the roadside. But to their surprise, they found that the leaves and flowers of these roadside plants were comparatively very dull. Can you help them to know why?
Solution:
The leaves and flowers of the roadside plants are very dull because the air along the roadside is polluted with air pollutants due to emissions from vehicles and industries, etc.
Thus, the roadside plants had probably some dust and soot deposited on them. This made them to appear dull.