MP Board Class 6th Science Solutions Chapter 15 Air Around Us

MP Board Class 6th Science Solutions Chapter 15 Air Around Us

Air Around Us Textbook Exercises

Question 1.
What is the composition of air?
The composition of air is:

• Nitrogen: 78.08%
• Oxygen: 20.95%
• Carbon dioxide: 0.034%
• Argon: 0.93%
• Helium: traces
• Water vapours: Traces

Thus, we see that air contains mostly nitrogen and oxygen. From above, it is clear that these two geses together make up 98% of the air.

Question 2.
Which gas in the atmosphere is essential for respiration?
Oxygen gas in the atmosphere is essential for respiration.

Question 3.
How will you prove that air supports burning?
This can be shown by following experiment:
Take a candle. Fix it on a table. Now light it. It starts burning. Then cover it with a glass cover so that all air supply is stopped. We will see that it stops burning after some time. As soon as air inside the glass is used up, the candle stops burning. This shows that air is necessary for burning.

Question 4.
How will you show that air is dissolved in water?
Take some water in a glass vessel or beaker. Heat it slowly on a tripod stand. We see that tiny bubbles are sticking on it. These bubbles came from the air dissolved in water. When we heat water, the air dissolved in water escapes out in the form of bubbles. This shows that air is dissolved in water.

Question 5.
Why does a lump of cotton wool shrink in water?
A lump of cotton wool shrink in water because the air inside cotton wool is driven out by water. They layers stick together and hence the lump of cotton wool shrinks.

Question 6.
The layer of air around the earth is known as?
Atmosphere.

Question 7.
The components of air used by green plants to make their food, is?
Carbon – dioxide.

Question 8.
List five activities that are possible due to the presence of air.
The some activities that are possible due to the presence of air:

1. Windmill
2. Winnowing
3. Respiration
4. Flying of aeroplanes, birds, etc.
5. Transpiration.

Question 9.
How do plants and animals help each other in the exchange of gases in the atmosphere?
Plants use carbon – dioxide to make their food and give out oxygen. The animals take oxygen for respiration and give out carbon – dioxide. This makes the balance of oxygen and carbon – dioxide in atmosphere. But if the green plants do not take in carbon – dioxide and give out oxygen, after some times there will no more oxygen on the earth and all living beings will die. That means, say, no life on earth. Thus, we can say that plants and animals help each other in the exchange of gases in the atmosphere.

Air Around Us Text Book Questions

Question 1.
Boojho is asking you, why do you think, the policeman in figure is wearing a mask?

Policemen is wearing a mask to save his mouth and nose from dust particles and smoke due to the fuel burning in vehicles.

Question 2.
Paheli wants to know, why the transparent glass of windows, if not wiped off regularly, appears hazy?
The transparent glass of windows wiped off regularly because the dust particles settle down on the glass.

Question 3.
Boojho want to know, why during an incident of fire, one is advised to wrap a woollen blanket over a burning object.
Woollen blanket do not pass oxygen which supports burning. Hence, the burning will stop.

Question 4.
Here is a question from Paheli, “Will the tiny air bubbles seen before the water actually boils, also appear if we do this activity by reheating boiled water kept in an air tight bottle?” If you do not know the answer you may try doing it and see for yourself.
No, in this case tiny air bubbles will not seen before the water actually boils.

Air Around Us Additional Important Questions

Air Around Us Objective Type Questions

Question 1.
Chose the correct answer:

Question (i)
Which of the following gases is not found free in air –
(a) Oxygen
(b) Nitrogen
(c) Hydrogen
(d) Carbondioxide.
(c) Hydrogen

Question (ii)
The most abundant constituent of air is –
(a) Nitrogen
(b) Oxygen
(c) Carbondioxide
(d) Water vapour.
(a) Nitrogen

Question (iii)
The percentage of oxygen by weight in the air is about –
(a) 78%
(b) 21%
(c) 23%
(d) 19%
(b) 21%

Question (iv)
Air is –
(a) A compound
(b) A mixture
(c) An element
(d) An electrolyte.
(b) A mixture

Question (v)
The constituent of air that is essential for life but does not support combustion is –
(a) Nitrogen
(b) Oxygen
(c) Carbondioxide
(d) Water vapor.
(a) Nitrogen

Question 2.
Fill in the Blanks:

1. The cover of air around the earth is called ……………….
2. Air occupies ………………. and has
3. Air is ………………. of gases.
4. The major components of air are ………………. and ……………….
5. Air is a ………………. of gases.
6. Lime water is ………………. dissolved in water.
7. Lime water turns ………………. when carbon – dioxide is passed through it.
8. Carbon – dioxide is formed when is burned.
9. Candle burns in the atmosphere due to ……………….
10. ………………. does not support burning.

1. Atmosphere
2. Space, mass
3. Mixture
4. Nitrogen, oxygen
5. Mixture
6. Lime
7. Milky
8. Fuel
9. Oxygen
10. Nitrogen.

Question 3.
Which of the following statements are true (T) or false (F):

1. Air is necessary for burning.
2. Air helps in dispersal of seeds.
3. Compressed air is used in the break system for stopping trains.
4. Fan circulates the air.
5. Birds can fly without air.
6. Air helps in pollination of seeds.
7. Animals can prepare food by photosynthesis.
8. Fishes can even breathe in water.
9. Plants do not use oxygen.
10. Oxygen is less on mountains.
11. Patients get oxygen from clyinders in case of any breathing problem.
12. Wind energy can be harnessed by a wind mill.

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

Question 4.
Match the items in Column A with the Column B:

(i) (e)
(ii) (c)
(iii) (a)
(iv) (b)
(u) (d).

Air Around Us Very Short Answer Type Questions

Question 1.
What is air ?
Air is gaseous substance.

Question 2.
What is atmosphere?
The cover of air all around earth is called atmosphere.

Question 3.
What is the height of atmosphere above earth?
Height of atmosphere is many hundred km above earth surface.

Question 4.
What is the height of clouds?
Clouds are about 16 km above the earth surface.

Question 5.
When there is no food in your lunch – box, what is present in it?
Only air is present.

Question 6.
Can you compress air?
Yes, we can compress air. When we fill football with air we compress air.

Question 7.
At what height, generally the jet planes fly?
Jet planes fly above clouds that mean at the height of more than 16 km from earth surface.

Question 8.
Name the components of air?
Components of air are:

1. Oxygen
2. Nitrogen
3. Carbon – dioxide
4. Water vapours and
5. Dust particles.

Question 9.
What percentage of notrogen is present in air?
Nearly 78% of air is nitrogen.

Question 10.
Which gas of air we use during respiration?
Oxygen is used during respiration.

Question 11.
Give some examples where carbon dioxide is formed.
Carbon – dioxide is formed when

1. Fuel burns,
2. Animals respire.

Question 12.
Who established for the first time that air contains more than one gases?
The French scientist, Antoine Laurent Lovoisier in 1789.

Question 13.
Which gas is necessary for all living organisms?
Oxygen.

Question 14.
How do fish respire in water?
The fish take dissolved oxygen from water for respiration.

Question 15.
Which gas is given out during photosynthesis?
Oxygen.

Question 16.
What is respiration?
In respiration oxygen is taken up by all living organisms and used to break down food to give carbon – dioxide and energy.

Question 17.
How much air does a person take in per day?
16 kg of air per day.

Question 18.
How does the air reduce harmful effects of smoke?
Air spreads the smoke to a large area. Thus the smoke layer becomes thin and its harmful effect is decreased.

Question 19.
Why do clothes dry faster in wind?
Rate of evaporation increases in wind and thus clothes dry faster in wind.

Question 20.
Why do we have gaps in firewood chulha?
These gaps make air available all around the wood for continuous burning.

Question 21.
Why do factories have chimneys?
Chimneys take smoke to a height. Air speeds is all over and effect of smoke decreases.

Question 22.
Why does a man sitting under a fan feel cooler?
Fan circualtes the air and makes the evaporation of sweat rapid. Evaporation causes cooling and thus man feels cooler.

Question 23.
Why do we fill compressed air in tyres?
Such tyres make transport smooth and easier.

Question 24.
What makes air impure?
The presence of dust particles, dirt, increase percentage of carbon-dioxide, sulphur dioxide and smoke make the air impure.

Question 25.
Mention three objects which are inflated by air and are used commonly.
Following objects are inflated by air:

1. Tyres of vehicles
2. Balloons
3. Footballs.

Air Around Us Short Answer Type Questions

Question 1.
Mentions five uses of air.
Uses of air are:

1. All living things use air for respiration.
2. Air is necessary for burning.
3. Air is necessary for decay of waste material.
4. Air can be used to produce energy by wind mill.
5. Air helps in the dispersal of seeds from one place to other place.

Question 2.
Define a wheather cock.
A wheather cock is a device which shows the direction of flow of air at that place.

Question 3.
What is photosynthesis?
Process of making food by the green leaves of plant with the help of carbon – dioxide, water and sunlight is known as photosynthesis.

Question 4.
Who maintains the balance of oxygen and carbon – dioxide in nature?
Plants and animals maintain the balance of oxygen and carbon – dioxide in nature. It follows as:

1. We breathe in oxygen and breathe out carbon – dioxide.
2. Plants use up carbon-dioxide when they produce food and oxygen.
3. Plants also use oxygen but they produce more than they use.

Question 5.
How will you show that air is a matter?
To show that air is a matter, we have to show that air occupies space and air has mass. Take a balloon. Blow air in it. The size of ballon increases. This shows that air occupies space. Take another balloon. Weight it empty. Then fill it with air. Again weight. We will see after filling air the weight of balloon is more. This shows that air has mass. These two experiments show that air is a matter.

Question 6.
How will you show the presence of carbon – dioxide in air?
Take a bottle filled with lime water. Then blow air from your mouth with the help of a pipe. The lime water will turn milky after some time. The carbon – dioxide present in air (from mouth) makes the lime water milky. This shows that carbon-dioxide is present in air.

Question 7.
When you finish your work in a laboratory you put the lid back on the spirit lamp. What happens then? Why?
When we put the lid back on the spirit lamp it stops burning because on putting the lid air does not reach to lamp. It thus puts out spirit lamp.

Question 8.
Why do mountaineers and divers carry oxygen cylinders with them?
At high altitudes on the mountains and deep in the sea the oxygen becomes very less. Due to less oxygen breathing becomes difficult. So mountaineers and divers carry oxygen cylinder with them.

Question 9.
Plants use carbon – dioxide for making their food. Where does this carbon – dioxide come from in the atmosphere?
Plants use carbon – dioxide for making their food. But animals use oxygen for respiration and gives out carbon – dioxide. So this makes the balance of oxygen and carbon – dioxide in atmosphere.

Question 10.
How will you show that air is present in a lump of soil?
The presence of air in a lump of soil can be shown by following experiment:
Take a lump of soil and put it into a plastic trough, half filled with water. We will see the bubbles of air coming out. These bubbles show that air is present in the lump of soil.

Question 11.
When you set fire to pieces of paper, it burns well. But when you set fire to a crumpled ball of paper, it burns only at the edge. Why is it so?
Air is essential for burning. A piece of paper burns easily because it gets good supply of air. But in a crumbled ball of paper, it burns only at the edge. The inner layer does not get air.

Question 12.
Discuss the role of plants in the environment?

1. Plants maintain balance between carbon – dioxide and oxygen in the atmosphere.
2. They act as noise and light filters.
3. They tend to lower down the atmosphere.

Question 13.
Draw a pie diagram showing the composition of air?

Air Around Us Long Answer Type Questions

Question 1.
How will you show that an empty bottle is filled with air?
We perform the following experiment to show that empty bottle is filled with air:
Take a glass trough. Fill half of it with water. Introduce an inverted glass bottle into the water. We will see that water does not enter it. Now tilt the bottle slightly. We will find that bubbles of air escape through water and water starts filling in the bottle. This shows that water in the bottle is filled only when air comes out of bottle. This shown that even empty bottle is filled with air.

Question 2.
How will you show that air contains water vapours?