Class 6 Chemistry Chapter 15 – Air Around Us Important Questions with Answers

Is Air Present Everywhere Around Us?

Question 1. What are the properties of air?
Answer:

• Air occupies space.
• Air is present everywhere around us.
• Air has no colour and one can see through it.
• It is transparent.

Question 2. What is atmosphere?
Answer: Our earth is surrounded by a thin layer of air. This layer is called atmosphere. It extends up to many kilometres above the surface of the earth.

Question 3. Why is atmosphere called the place where exchange of gases in nature occurs?
Answer: We know that various gases are found in air. Now some organisms live on land, some in water and some deep under the soil. But all need oxygen to respire. The terrestrial organisms take oxygen from the atmosphere. You know that during respiration by living beings and burning of materials, carbon dioxide is produced along with some other gases. Also Co₂ is used by the plants in the process of photosynthesis in which oxygen is released. All gases go into the atmosphere. Thus, it is a place in nature for gaseous exchange

Question 4. What do you mean by relative humidity?
Answer: The content of water vapour in the air is expressed in terms of humidity or relative humidity.

Question 5. The mountaineers carry oxygen cylinder with them while climbing high mountains. Why?
Answer: The availability of air decreases gradually as we go up in the atmosphere.

Also Check: CBSE Syllabus Class 1 to 12

What is air made up of ?

Question 1. How will you prove that air is a mixture of several gases and not a compound?
Answer: The following points show that air is a mixture:

1. The composition of air varies slightly from place to place.
2. Different components of air are separable by physical processes.
3. Different components of air exhibit their characteristics, for example, O₂ in air supports combustion, CO₂ in air turns lime water milky.

Question 2. Name the substances which are present in traces in air. What are these together called?
Answer: Xenon (Xe), Krypton (Kr), Neon (Ne) and Helium (He) are present in traces in the air. These together form 0.02% of air and are called inert gases.

Question 3. Describe the composition of air.
Answer: Air contains mostly nitrogen (78.03%) and oxygen (20.99%). The remaining 1% (by volume) is shared by argon (0.34%), carbon dioxide (0.33%), other noble gases, oxides of nitrogen and sulphur etc., in the decreasing order.

Question 4. What will happen if the amount of oxygen is increased in the air?
Answer: Air will become more combustible and many substances may undergo fast oxidation.

Question 5. Why are fine hair and mucus present in our nostrils? Why should we not breathe in by mouth?
Answer: We inhale air when we breathe through our nostrils. We also know that air contains dust particles. To prevent dust particles from getting into the respiratory system, fine hair and mucus are present inside the nose.
Since, our mouth does not contain the above discussed barriers of dust, so if we breathe through it, dust particles may enter in our respiratory tract. That is why breathing through mouth is not suggested.

Question 6. Name the gases present in air. Which one of them is most abundant?
Answer: N₂, O₂, Ar (argon), CO₂, water vapour, neon (Ne), helium (He), krypton (Kr), xenon (Xe) are present in air. Nitrogen is most abundant.

Question 7. Name the vital component of air. Specify its importance.
Answer: Oxygen is regarded as the most important and vital component of air. The living beings take in oxygen (respiration) and give off carbon dioxide. The oxygen used is replaced by plants in photosynthesis. The concentration of oxygen in the air is thus maintained. Thus, it is very important to sustain life on the earth.

Question 8. Explain with flow diagram oxygen-carbon dioxide balance in the atmosphere.
Answer: Oxygen-carbon dioxide balance is the balance between the rate of consumption and formation of oxygen and carbon dioxide in nature.

Question 9. Why do we feel suffocated in a closed room if something is becoming there?
Answer: We feel suffocated in a closed room if some material is burning there because burning causes excess of carbon dioxide and its accumulation causes suffocation.

Question 10. What is the role of long chimneys in factories?
Answer: Burning of fuel takes place in factories, it produces smoke which contains a few harmful gases and fine dust particles. The chimneys in factories take the harmful smoke and gases away from us.

Question 11. Why do policemen regulating traffic at a crowded crossing often wear a mask?
Answer: Wearing a mask at a crowded crossing saves the policemen from harmful smoke and dust particles emitted by vehicles, which may enter their nose.

Activity 3.
In the presence of your teacher, fix two small candles of the same size in the middle of two shallow containers. Now, fill the containers with some water. Light the candles and then cover each one of them with an inverted glass (one much taller than the other) as shown in the figure. Observe carefully what happens to the burning candles and the water level.

Do the candles continue to burn or go off? Does the level of water inside glasses remain the same?

Candles go off after some time because supply of oxygen, necessary for burning, has been stopped. No, the level of the water inside glasses rises up when the candles blow out.

How Does Oxygen Become Available To Animals And Plants Living In Water And Soil?

Question 1. What is the importance of oxygen in daily life?
Answer: Oxygen plays a very important role in our daily life. Some of these are:

• As ozone, it provides a blanket in the atmosphere which protects us from harmful ultraviolet radiations emitted by the sun.
• It is used for breathing and as a breathing aid in hospitals, aeroplanes, and by deep-sea divers and astronauts

Question 2. Why is air dissolved in water richer in oxygen than ordinary air?
Answer: The air dissolved in water is richer in oxygen because oxygen has appreciable solubility in water, whereas nitrogen is insoluble in water.

Question 3. How does oxygen become available to the animals in water and soil?
Answer. Air remains dissolved in water. Air is also present between the particles of soil. Hence animals living there get oxygen.

Question 4. Are respiration and breathing same?
Answer. Breathing is just the intake of oxygen and giving out carbon dioxide.
Respiration is a chemical process which generates energy in body.

Question 5. Why do earthworms come out of the soil during heavy rains?
Answer: When it rains heavily, water fills up all the spaces occupied by the air in the soil. In such a situation, animals like earthworms need to come out of the soil for respiration.

How Is The Oxygen In The Atmosphere Replaced?

Question 1. How does oxygen occur in nature?
Answer: Oxygen is found in free state in air as diatomic molecule (O₂) to the extent of 21% by volume or 23% by weight. In the combined state, it is present in water (89% by weight), earth’s crust (about 50%) and in plants and animal tissues (50-70%).

Question 2. What happens if the percentage of oxygen in the air reaches to 70%?
Answer. If any substance catches fire, it will become difficult to extinguish the fire, as oxygen supports combustion.

Question 3. What is the importance of the presence of carbon dioxide in the atmosphere? What will happen if its concentration in the air increases?
Answer: Carbon dioxide has the property of absorbing heat rays called infrared rays. Nature has a balance of carbon dioxide in the atmosphere, thus giving an optimum warmth to the atmosphere. The increase in the concentration of carbon dioxide in the air would cause increase in the temperature of the earth and would ultimately lead to melting of glaciers causing floods etc. This phenomenon is called global warming.

Question 4.Nature maintains a balance of carbon dioxide and oxygen in the atmosphere..
Answer: Nature in its own way has been maintaining a balance of carbon dioxide and oxygen in the atmosphere. Atmosphere and oceans are continuously exchanging these gases with the rocks, plants and living organisms. However, due to rapid industrialization in the past, the concentration of CO₂ near the earth’s surface is increasing though in very small proportions till now.

Question 5. Define oxygen cycle.
Answer: The cycle of consumption of oxygen by respiration and its release by photosynthesis is called oxygen cycle.

Question 6. How is air important for life on the earth?
Answer: Air helps in the movements of sailing yachts, gliders, parachutes and aeroplanes. Birds, bats and insects can fly due to the presence of air. Air also helps in the dispersal of seeds and pollen of flowers of several plants. Air plays an important role in water cycle. Thus air is important for life on the earth.

Activity 4
Find a sunny room in your school/home. Close all the doors and windows with curtains pulled down to make the room dark. Now, open the door or a window facing the sun, just a little, in such a way that it allows sunlight to enter the room only through a slit. Look carefully at the incoming beam of sunlight.

Do you see some tiny shining particles moving in the beam of sunlight (Fig.)? What are these particles?
Yes, some tiny shining particles are seen moving in the beam of sunlight. These are the dust particles which are present in air.

Objective Type Questions

Question 1. 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:

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.

Question 2: Fill in the blanks with the appropriate Words

1. When air is in ………………. it is called wind.
2. Air has no ……………. and one can see through it. It is ………………… .
3. Air is really not one substance but a ……………………. .
4. Air contains ………………… particles.
5. The component of air that supports burning is called …………………… .
6. The oxygen helps in breaking down the digested food in the body to release the …………………….. .
7. Our earth is surrounded by ……………………….. .
8. Initial drops of first rain bring a lot of …………………… along with them.
9. The aquatic animals use dissolved oxygen in water for respiration. This is possible because oxygen is ………………… in water.
10. Nitrogen of the air is used on a large scale to manufacture ………………………. .
11. Air is present in, atmosphere, water and ……………….. .
12. The method of separating two components of a mixture which is based on the wind is …………………….. .
13. ……………………. air is used in tyres of vehicles.
14. …………………. is the place in nature for gaseous exchange.

Answers:

1. motion
2. colour, transparent
3. mixture
4. dust
5. oxygen
6. energy
7. air
8. dirt
9. soluble
10. fertilizers
11. soil
12. winnowing
13. Compressed
14. Atmosphere

Question 3. State whether the statements given below are True or False:

1. We cannot see air.
2. Air is a compound and not an element. ‘
3. A firki rotates only in an open area or in a closed room with the ceiling fan switched on.
4. Open areas allow air to move here and there.
5. Air is an opaque material.
6. All living organisms require air for their survival.
7. Air contains water vapours.
8. We breath in CO₂ and breath out O₂.
9. A policeman, controlling the traffic wears a mask to prevent the dust particles from entering his respiratory system through breathing.
10. Air is necessary for burning things.
11. The major part of air is nitrogen.
12. Air becomes thinner and thinner as we go higher and higher from the surface of earth.
13. Plants produce oxygen through photosynthesis.
14. Plants do not respire.

Answers:

1. True
2. False
3. True
4. True
5. False
6. True
7. True
8. False
9. True
10. True
11. True
12. True
13. True
14. False

Question 4. Choose the correct option in the following questions:
(i) Major part of the air is constituted by
(a) nitrogen
(b) oxygen
(c) carbon dioxide
(d) inert gases
Answer: (a) 3/4th portion of air is nitrogen.

(ii) Which of the following gas helps in burning? ,
(a) Nitrogen
(b) Oxygen
(c) Carbon dioxide
(d) Carbon monoxide
Answer:
(b) Oxygen does not bum but supports burning.

(iii) Which of the following gas we use in breathing?
(a) Carbon dioxide
(b) Nitrogen
(c) Oxygen
(d) None of these
Answer:
(c) We use oxygen and produce carbon dioxide.

(iv) Wind is
(a) air around us
(b) rising hot air
(c) air in motion
(d) none of these
Answer:
(c) Air in motion is called wind.

(v) Air is present in
(a) atmosphere
(b) soil
(c) water of ponds, lakes and seas
(d) everywhere
Answer:
(d) Air is present everywhere.

(vi) Air is
(a) a mixture
(b) a pure substance
(c) an element
(d) anything, that depends on the place where it is found
Answer:
(a) Air is a mixture of various gases, water vapours and dust particles.

(vii) Envelope of air that surrounds the earth is known as
(a) biosphere
(b) atmosphere
(c) environment
(d) ecosystem
Answer:
(b) Air is all around us, a thick layer of air surrounds the earth, this blanket of air is called atmosphere.

(viii) 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:
(d) Air is a homogeneous solution, which occupies space and it is transparent. So air is not a compound.

(ix) The ratio of nitrogen to oxygen in the air is
(a) 1: 4
(b) 4:1
(c) 3: 1
(d) 1:2
Answer:
(b) 4:1 is the ratio of nitrogen to oxygen in the air.

(ix) The main constituent of the air is.
(a) nitrogen
(b) oxygen
(c) carbon dioxide
(d) hydrogen
Answer:
(a) 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.

Class 6 Chemistry Chapter 15 FAQs

What is air class 6 very short answer?

Air is the invisible mixture of gases that surrounds the Earth.

How will you prove that air supports burning (Class 6 Science - Chapter 15)?

By showing that a flame goes out when we cover it with a glass jar, proving that air is needed for burning.

How much air do we use in a day Class 6?

We use about 15,000 liters of air every day through breathing.