CBSE Grade 6 Science Chapter 15 - Air Around Us

  

NCERT TEXTBOOK EXERCISES

(Pages 153-154)

Question 1.
What is the composition of air?
Answer :
Air contains 99% nitrogen and oxygen. The remaining 1% is carbon dioxide and a few other gases, water vapour and 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 center 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-liter plastic water bottle and with the help of a 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-liter plastic water bottle. Next, make several holes all over the surface of a 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. The 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 :
We take some water in a beaker and heat it slowly on a tripod stand. We see that well before the water begins to boil, tiny bubbles of air are seen on the inside of the beaker. This shows that air is dissolved in water

Question 5.
Why does a lump of cotton wool shrink in the 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 :
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 respiration in living beings.
3. It is helpful in the movements of sailing yachts, gliders, parachutes, and air crafts.
4. Air current makes the windmill 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 the 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 :
Animals produce carbon dioxide during respiration and use oxygen whereas plants use carbon dioxide and produce oxygen during photosynthesis. In this way, plants and animals help each other in the exchange of gases in the atmosphere.

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Extra Questions for Class 6 Science Chapter 15 Air Around Us with Answers Solutions

Air Around Us Class 6 Extra Questions Very Short Answer Type

Question 1.
Name some musical instruments in which air plays an important role.
Answer:
Flute, saxophone, trumpet, horn, etc.

Question 2.
What do human beings release during respiration?
Answer:
Co2

Question 3.
What is the layer of air that surrounds the earth is called?
Answer:
Atmosphere

Question 4.
What is the necessary condition for the combustion to take place?
Answer:
Presence of air

Question 5.
Which gas is present in the atmosphere which is essential for breathing?
Answer:
Oxygen

Question 6.
Which component of air acts as a supporter of combustion?
Answer:
Oxygen

Question 7.
Which component of air acts as a non-supporter of burning?
Answer:
Nitrogen and carbon dioxide.

Question 8.
Why transparent glass window becomes hazy, if not wiped off regularly?
Answer:
Because dust particles settle on it.

Question 9.
Name one insect which lives deep under the soil.
Answer:
Earthworm

Question 10.
What is moving air called?
Answer:
Moving air is called wind.

Question 11.
Which gas is the major component of air? State its composition.
Answer:
Nitrogen gas (78%)

Question 12.
What is the relative proportions of nitrogen and oxygen in the air?
Answer:
4:1

Question 13.
Name a device which uses wind energy to generate electricity.
Answer:
Windmill

Question 14.
Name the device which shows the direction of wind.
Answer:
Weather cock

Question 15.
Why do earthworms come out of the soil during heavy rains?
Answer:
During heavy rain, water fills up the spaces occupied by air. So earthworms have to come out to breathe air.

Air Around Us Class 6 Extra Questions Short Answer Type

Question 1.
Why air is considered as mixture?
Answer:
Air contains oxygen and nitrogen as its major constituents along with carbon dioxide, and other gases. These gases retain their properties in air. So, the air is called a mixture.

Question 2.
Name the major constituents of air. Also give their volume proportions in air.
Answer:

Name of-constituents	% Composition
Nitrogen	78.1%
Oxygen	20.9%
Carbon dioxide	0.03%
Argon	0.9%
Other components of air are water vapour and dust particles.

Question 3.
What is atmosphere?
Answer:
The thin layer of air that surrounds the earth as an envelope is called atmosphere.

Question 4.
What is smoke?
Answer:
The dark-coloured gases caused by burning of anything is called smoke.

Question 5.
State the properties of air.
Answer:
Properties of air are as follows:

1. It is colourless
2. It is transparent
3. It is compressible
4. It occupies space
5. It is soluble in water
6. It has mass

Question 6.
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 7.
State the properties of oxygen gas.
Answer:
Oxygen is a colourless, tasteless and odourless gas. It is soluble in water. Oxygen gas is essential for breathing (or respiration).

Question 8.
Why do you think, policemen wear masks?
Answer:
Policemen wear masks to prevent dust particles from getting into their respiratory system.

Question 9.
What do you mean by relative humidity?
Answer:
The content of water vapour in the air is expressed in the terms of humidity or relative humidity.

Question 10.
Why during an incident of fire, one is advised to wrap a woollen blanket over a burning object.
Answer:
Air is supporter of combustion. To cut-off the supply of air from the burning object it is advised to wrap a woollen blanket around it.

Air Around Us Class 6 Extra Questions Long Answer Type

Question 1.
What is the importance of water vapour in air?
Answer:
When air comes in contact with a cool surface, it condenses and forms tiny drops of water on the cooled surfaces. The presence of water vapour in the air is important for maintaining the water cycle in nature.

This is because it is water vapour present in the air which rises high in the sky along with hot air, get cooled, condenses to form clouds and then brings rain on the earth.

Question 2.
Explain briefly carbon dioxide gas and its properties.
Answer:
Carbon dioxide is a colourless and odourless gas. It is soluble in water. It neither burns nor supports burning. Co2 extinguishes a burning fire. Plants and animals consume oxygen for respiration and produce Co2 which is necessary for photosynthesis. It is an important greenhouse gas.

Question 3.
What are the uses of air?
Answer:
Air is useful to human beings in many ways. Some of the important uses of air are as follows:

1. It is used for breathing purpose.
2. It is used for burning fuels to make fire.
3. It helps the birds, bats and insects in flying.
4. It plays an important role in the water cycle in nature.
5. Compressed air is used in tyres of various kinds of vehicles.
6. It also helps in the dispersal of seeds and pollens of flowers of several plants.

Question 4.
Why the animals living deep inside the soil come out during heavy rains?
Answer:
The air is present in spaces between particles of soil. Animal living inside the soil get oxygen for breathing (or respiration) from the air present between the soil particles. However, when it rains heavily water fills up the spaces occupied by the air in the soil.

In this situation, the animals living inside the soil have to come out of the soil to obtain air for breathing. For example, the earthworms come out of the soil only during heavy rains.

Question 5.
Why we must always breathe in through our nose and not by our 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. This is why breathing through mouth is not suggested.

Air Around Us Class 6 Extra Questions HOTS

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

• The component of air varies from place to place.
• Components of air can be separated out.
• Different components of air retain their properties.

Question 2.
Why long chimneys are present in factories?
Answer:
Most of the factories produces harmful smoke and gases. So factories have long chimneys to carry these harmful gases away from our noses.

Question 3.
How nature maintains a balance of Co2 and o2 in atmosphere?
Answer:
Plant releases oxygen which is consumed by animals in the process of respiration. Animals release carbon dioxide which is consumed by the plants for the process of photosynthesis.

Question 4.
There are two colourless and odourless gases in jars A and B. One is oxygen and other is carbon dioxide. How will you detect which jar contain oxygen and which contain carbon dioxide gas?
Answer:
We can detect the gas as oxygen or carbon dioxide by bringing a burning splinter near the mouth of the jars. The gas which will support burning is oxygen gas and which will not support burning, i.e., extinguishes a burning splinter, is carbon dioxide gas.

Question 5.
Why is atmosphere important for sustenance of life on the earth?
Answer:
Atmosphere is important for the following reasons:

1. It keeps the temperature of earth fairly constant.
2. It contains all the gases essential for sustaining life.
3. It protects us from harmful UV radiations.
4. It maintains water cycle.

Air Around Us Class 6 Extra Questions Value Based (VBQs)

Question 1.
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. She was amazed and asked about this phenomenon to her science teacher.
(a) Why Garima observed tiny bubbles inside the bottle?
(b) What will happen to the bubbles if we bring it back to normal room temperature?
(c) When do we see the above phenomenon in nature and what is its significance?
(d) What values of Garima is shown here?

Answer:
(a) As the water in the bottle get warm due to the heat of sunlight air dissolved in it escaped and appeared as tiny bubbles.
(b) Tiny bubbles will again disappear in the water.
(c) We see the above phenomenon in summer season when oxygen dissolved in water reduces due to hot temperature and because of this aquatic life suffers.
(d) Garima is observable, intelligent, curious girl with scientific temperament.

Question 2.
While going for a local excursion to a deserted area, Vikas wore a mask. When boarding the school bus his friends made fun of him that he was looking odd and beside enjoying he is taking extra precautions. But when going through the dry roads all of his friends felt the need of the mask. He suggested everyone to tie handkerchief on their nose. It helped them a lot.
(a) What is dust?
(b) What are the health issues related with dust?
(c) How does a mask help?
(d) What values of Vikas is shown here?

Answer:
(a) Dust is tiny particles of earth or waste lying on ground or carried by the air.
(b) Dust particles badly effects our respiratory system. It may cause asthma, allergy, respiratory problems, etc.
(c) Mask acts as a barrier for the entry of dust particles directly into our nose. It filters the air.
(d) Vikas is intelligent, helpful and have future vision.