Here students can get info about NCERT Important Questions & MCQs for Class 6 Science so that they can get to know the answers to the questions in case they are not able to find it. You can find the best Class 6th Science NCERT Solutions explained in conformance with the CBSE curriculum for Class 6.
Table of Contents
Chapter 15 Air Around Us 6th Science
MCQs
Question 1.
Major part of the air is constituted by
(a) nitrogen
(b) oxygen
(c) carbon dioxide
(d) inert gases
Answer
Answer: (a) nitrogen
Explanation:
3/4th portion of air is nitrogen.
Question 2.
Which of the following gas helps in burning? ,
(a) Nitrogen
(b) Oxygen
(c) Carbon dioxide
(d) Carbon monoxide
Answer
Answer: (b) Oxygen
Explanation:
Oxygen does not bum but supports burning.
Question 3.
Which of the following gas we use in breathing?
(a) Carbon dioxide
(b) Nitrogen
(c) Oxygen
(d) None of these
Answer
Answer: (c) Oxygen
Explanation:
We use oxygen and produce carbon dioxide.
Question 4.
Wind is
(a) air around us
(b) rising hot air
(c) air in motion
(d) none of these
Answer
Answer: (c) air in motion
Explanation:
Air in motion is called wind.
Question 5.
Air is present in
(a) atmosphere
(b) soil
(c) water of ponds, lakes and seas
(d) everywhere
Answer
Answer: (d) everywhere
Explanation:
Air is present everywhere.
Question 6.
Air is
(a) a mixture
(b) a pure substance
(c) an element
(d) anything, that depends on the place where it is found
Answer
Answer: (a) a mixture
Explanation:
Air is a mixture of various gases, water vapours and dust particles.
Question 7.
Envelope of air that surrounds the earth is known as
(a) biosphere
(b) atmosphere
(c) environment
(d) ecosystem
Answer
Answer: (b) atmosphere
Explanation:
Air is all around us, a thick layer of air surrounds the earth, this blanket of air is called atmosphere.
Question 8.
Which is not a property of air?
(a) It occupies space.
(b) It is transparent,
(c) It is a solution.
(d) It is a compound.
Answer
Answer: (d) It is a compound.
Explanation:
Air is a homogeneous solution, which occupies space and it is transparent. So air is not a compound.
Question 9.
The ratio of nitrogen to oxygen in the air is
(a) 1:4
(b) 4:1
(c) 3:1
(d) 1:2
Answer
Answer: (b) 4:1
Explanation:
4:1 is the ratio of nitrogen to oxygen in the air.
Question 10.
The main constituent of the air is.
(a) nitrogen
(b) oxygen
(c) carbon dioxide
(d) hydrogen
Answer
Answer: (a) nitrogen
Explanation:
Composition of air (Percentage by volume), nitrogen = 78.03, oxygen = 20.99, carbon dioxide = 0.03, noble gases = 0.95 and some water vapours, dust particles and other impurities.
Match the following items given in Column A with that in Column B:
Column A | Column B |
(a) Air | (i) Thin layer of air surrounding our earth. |
(b) Wind | (ii) Released in respiration. |
(c) Atmosphere | (iii) Makes three fourth part of total air. |
(d) Oxygen | (iv) Is process of burning of food to get energy. |
(e) Carbon dioxide | (v) Uses wind power to rotate. |
(f) Nitrogen | (vi) Process of preparation of food by green plants. |
(g) Respiration | (vii) Allow air to move here and there. |
(h) Photosynthesis | (viii) Is a gaseous mixture. |
(i) Windmill | (ix) Supports combustion. |
(j) Open areas | (x) Is air in motion. |
Answer
Answer:
Column A | Column B |
(a) Air | (viii) Is a gaseous mixture. |
(b) Wind | (x) Is air in motion. |
(c) Atmosphere | (i) Thin layer of air surrounding our earth. |
(d) Oxygen | (ix) Supports combustion. |
(e) Carbon dioxide | (ii) Released in respiration. |
(f) Nitrogen | (iii) Makes three fourth part of total air. |
(g) Respiration | (iv) Is process of burning of food to get energy. |
(h) Photosynthesis | (vi) Process of preparation of food by green plants. |
(i) Windmill | (v) Uses wind power to rotate. |
(j) Open areas | (vii) Allow air to move here and there. |
Fill in the blanks with the appropriate Words.
1. When air is in ………………. it is called wind.
Answer
Answer: motion
2. Air has no ……………. and one can see through it. It is ………………… .
Answer
Answer: colour, transparent
3. Air is really not one substance but a ……………………. .
Answer
Answer: mixture
4. Air contains ………………… particles.
Answer
Answer: dust
5. The component of air that supports burning is called …………………… .
Answer
Answer: oxygen
6. The oxygen helps in breaking down the digested food in the body to release the …………………….. .
Answer
Answer: energy
7. Our earth is surrounded by ……………………….. .
Answer
Answer: air
Important Questions
1. Name the main component of air.
Ans: Nitrogen gas
Ans: Photosynthesis by green plants is source of oxygen gas in air.
Ans: 78.1%
Ans: 20.9%
Ans: Respiration by animals and plants and burning of fuel.
Ans: Presence of air.
1. Why is air considered as a mixture?
Ans: Air contains oxygen and nitrogen as its major constituents of air. These gases retain their properties in air. So the air is called a mixture.
Ans: (a) Oxygen (b) Carbon dioxide.
Ans: Rusting of iron takes place in the presence of moisture and air. So the presence of air and water vapour in air are two necessary conditions for rusting of iron.
Ans: Windmills use the wind energy to convert wind energy into electrical energy
Ans: Blowing air is called wind. Wind possesses kinetic energy. The kinetic energy possessed by wind is called wind energy.
Uses of Wind Energy are:
(i) Wind energy is used to pump the ground water.
(ii) Wind energy is used to generate electricity with the help of windmills.
Ans: The two uses of air are as below:
(a) For respiration all organisms need air.
(b) For burning of any substance air is needed.
Ans: The oxygen in air is used by the organisms present in air, water or soil or on earth for their respiration. During respiration carbon dioxide gas is released to air. But green plants during photosynthesis use carbon dioxide of air for preparing food and they release oxygen gas in the air. Thus the balance of oxygen in air is maintained.
Ans: If any substance catches fire it will become difficult to extinguish the fire, as oxygen supports combustion.
Ans: The increased percentage of carbon-dioxide will cause green house effect, i.e. it will not allow the hot rays of sun to escape from the atmosphere after reflection once they enter the earth’s atmosphere, thereby increasing the temperature of earth, ice on mountains will melt and water level will rise.
Ans: All these animals live in underground burrows or remain buried in the soil. They get oxygen from air that enters into the burrow through entrance of burrow or through pores in the soil. But when it rains, the water gets filled in their dwelling places and pores of the soil. So, they come out in search of air.
Ans: It is because carbon-dioxide does not support combustion. When sprayed on burning object it stops the supply of oxygen and extinguishes fire.
Ans: Take a glass tumbler add some soil in it, then pour some water on the soil slowly, the air-bubbles comes out of the soil. This proves that soil holds air in it.
Ans: The dust particles which remain suspended in air get loaded and come down on the ground due to rainfall, this is the reason that the sky and the air look clean and clear after rainfall.
Ans: As you go up, above the sea-level the atmospheric pressure goes on decreasing and the amount of oxygen also decreases at higher altitude.
Ans: Blanket cuts the supply of oxygen to the object that is burning, thereby prevents it from further burning.
1. What is air? Name the major constituents of air. Also give their volume proportions in air.
Ans: Air is a mixture of gases. The major constituents of air are nitrogen, oxygen, carbon dioxide and argon. The percentage composition of constituents of air are as given below:
Other components of air are water vapour and dust particles.
Ans: Aim of experiment: To show that air contains nitrogen and oxygen in the ratio 4 : 1 by volume:
Procedure: Take a glass container and fix a candle at its centre. Put some quantity of water in the container. Place an empty, dry gas jar over it. Mark five marks above water surface on the jar at equal distances shown in the figure given below.
The candle is lightened and is covered with the gas jar. After some time the candle is extinguished and the water level is raised in gas jar. The raised level in water is 1 / 5 of the volume of air in the gas jar.
This proves that one part of the air of the jar is a gas which supports combustion, i.e., oxygen. Hence, 1/5 by volume is oxygen in air.
Ans: The components of mixture can be easily separated and they retain their properties.
The components of air are: oxygen, nitrogen, water vapour and carbon-dioxide, all these gases can be easily separated and they retain their properties.
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