NCERT Textbook - Air around Us Class 6 Notes | EduRev

General Science for UPSC (Civil Services) Prelims

Created by: Praveen Kumar

Class 6 : NCERT Textbook - Air around Us Class 6 Notes | EduRev

 Page 1


15
Air Around us
W
e have learnt in Chapter 9 that
all living things require air.
But, have you ever seen air?
You might not have seen air, but, surely
you must have felt its presence in so
many ways. You notice it when the
leaves of the trees rustle or the clothes
hanging on a clothes-line sway. Pages
of an open book begin fluttering
when the fan is switched on. The moving
air makes it possible for you to fly your
kite. Do you remember Activity 3 in
Chapter 5 in which you separated the
sand and sawdust by winnowing?
Winnowing is more effective in moving
air. You may have noticed that during
storms the wind blows at a very high
speed. It may even uproot trees and blow
off the rooftops.
Have you ever played with a firki
(Fig. 15.1)?
Move it a little, back and
forth. Observe, what happens.
Does the firki rotate? What makes a firki
rotate — moving air, isn’t it?
Have you seen a weather cock
(Fig. 15.3)? It shows the direction in
which the air is moving at that place.
Fig. 15.1 Different types of  firki
Fig. 15.2 Making a simple firki
Fig. 15.3 A weather cock
Activity 1
Let us make a firki of our own, following
the instructions shown in Fig. 15.2.
Hold the stick of the firki and place it
in different directions in an open area.
15.1 IS AIR PRESENT EVERYWHERE
AROUND US?
Close your fist — what do you have in
it? Nothing? Try the following activity
to find out.
Activity 2
Take an empty glass bottle. Is it really
empty or does it have something inside?
Turn it, upside down. Is something
inside it, now?
©NCERT
not to be republished
Page 2


15
Air Around us
W
e have learnt in Chapter 9 that
all living things require air.
But, have you ever seen air?
You might not have seen air, but, surely
you must have felt its presence in so
many ways. You notice it when the
leaves of the trees rustle or the clothes
hanging on a clothes-line sway. Pages
of an open book begin fluttering
when the fan is switched on. The moving
air makes it possible for you to fly your
kite. Do you remember Activity 3 in
Chapter 5 in which you separated the
sand and sawdust by winnowing?
Winnowing is more effective in moving
air. You may have noticed that during
storms the wind blows at a very high
speed. It may even uproot trees and blow
off the rooftops.
Have you ever played with a firki
(Fig. 15.1)?
Move it a little, back and
forth. Observe, what happens.
Does the firki rotate? What makes a firki
rotate — moving air, isn’t it?
Have you seen a weather cock
(Fig. 15.3)? It shows the direction in
which the air is moving at that place.
Fig. 15.1 Different types of  firki
Fig. 15.2 Making a simple firki
Fig. 15.3 A weather cock
Activity 1
Let us make a firki of our own, following
the instructions shown in Fig. 15.2.
Hold the stick of the firki and place it
in different directions in an open area.
15.1 IS AIR PRESENT EVERYWHERE
AROUND US?
Close your fist — what do you have in
it? Nothing? Try the following activity
to find out.
Activity 2
Take an empty glass bottle. Is it really
empty or does it have something inside?
Turn it, upside down. Is something
inside it, now?
©NCERT
not to be republished
148 SCIENCE
Now, dip the open mouth of the bottle
into the bucket filled with water as
shown in Fig. 15.4. Observe the bottle.
Does water enter the bottle? Now tilt the
bottle slightly. Does the water now enter
the bottle? Do you see bubbles coming
out of the bottle or hear any bubbly
sound? Can you now guess what was
in the bottle?
Yes! You are right. It is “air”, that was
present in the bottle. The bottle was not
empty at all. In fact, it was filled
completely with air even when you
turned it upside down. That is why you
notice that water does not enter the
bottle when it is in an inverted position,
as there was no space for air to escape.
When the bottle was tilted, the air was
able to come out in the form of bubbles,
and  water filled up the empty space that
the air has occupied.
This activity shows that air occupies
space. It fills all the space in the bottle.
It is present everywhere around us. Air
has no colour and one can see through
it. It is transparent.
Our earth is surrounded by a thin
layer of air. This layer extends up to
many kilometres above the surface of
the earth and is called atmosphere.
Why do you think, mountaineers
carry oxygen cylinders with them, while
climbing high mountains (Fig. 15.5)?
Fig. 15.4 Experiments with an empty bottle.
Fig. 15.5 Mountaineers carry oxygen cylinders
with them
15.2 WHAT IS AIR MADE UP OF?
Until the eighteenth century, people
thought that air was just one substance.
Experiments have proved that it is really
not so. Air is a mixture of many gases.
What kind of a mixture is it? Let us find
out about some of the major
components of this mixture, one by one.
Water vapour
We have learnt earlier that air contains
water vapour. We also saw that, when
air comes in contact with a cool surface,
it condenses and drops of water appear
on the cooled surfaces. The presence of
water vapour in air is important for the
water cycle in nature.
Oxygen
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
©NCERT
not to be republished
Page 3


15
Air Around us
W
e have learnt in Chapter 9 that
all living things require air.
But, have you ever seen air?
You might not have seen air, but, surely
you must have felt its presence in so
many ways. You notice it when the
leaves of the trees rustle or the clothes
hanging on a clothes-line sway. Pages
of an open book begin fluttering
when the fan is switched on. The moving
air makes it possible for you to fly your
kite. Do you remember Activity 3 in
Chapter 5 in which you separated the
sand and sawdust by winnowing?
Winnowing is more effective in moving
air. You may have noticed that during
storms the wind blows at a very high
speed. It may even uproot trees and blow
off the rooftops.
Have you ever played with a firki
(Fig. 15.1)?
Move it a little, back and
forth. Observe, what happens.
Does the firki rotate? What makes a firki
rotate — moving air, isn’t it?
Have you seen a weather cock
(Fig. 15.3)? It shows the direction in
which the air is moving at that place.
Fig. 15.1 Different types of  firki
Fig. 15.2 Making a simple firki
Fig. 15.3 A weather cock
Activity 1
Let us make a firki of our own, following
the instructions shown in Fig. 15.2.
Hold the stick of the firki and place it
in different directions in an open area.
15.1 IS AIR PRESENT EVERYWHERE
AROUND US?
Close your fist — what do you have in
it? Nothing? Try the following activity
to find out.
Activity 2
Take an empty glass bottle. Is it really
empty or does it have something inside?
Turn it, upside down. Is something
inside it, now?
©NCERT
not to be republished
148 SCIENCE
Now, dip the open mouth of the bottle
into the bucket filled with water as
shown in Fig. 15.4. Observe the bottle.
Does water enter the bottle? Now tilt the
bottle slightly. Does the water now enter
the bottle? Do you see bubbles coming
out of the bottle or hear any bubbly
sound? Can you now guess what was
in the bottle?
Yes! You are right. It is “air”, that was
present in the bottle. The bottle was not
empty at all. In fact, it was filled
completely with air even when you
turned it upside down. That is why you
notice that water does not enter the
bottle when it is in an inverted position,
as there was no space for air to escape.
When the bottle was tilted, the air was
able to come out in the form of bubbles,
and  water filled up the empty space that
the air has occupied.
This activity shows that air occupies
space. It fills all the space in the bottle.
It is present everywhere around us. Air
has no colour and one can see through
it. It is transparent.
Our earth is surrounded by a thin
layer of air. This layer extends up to
many kilometres above the surface of
the earth and is called atmosphere.
Why do you think, mountaineers
carry oxygen cylinders with them, while
climbing high mountains (Fig. 15.5)?
Fig. 15.4 Experiments with an empty bottle.
Fig. 15.5 Mountaineers carry oxygen cylinders
with them
15.2 WHAT IS AIR MADE UP OF?
Until the eighteenth century, people
thought that air was just one substance.
Experiments have proved that it is really
not so. Air is a mixture of many gases.
What kind of a mixture is it? Let us find
out about some of the major
components of this mixture, one by one.
Water vapour
We have learnt earlier that air contains
water vapour. We also saw that, when
air comes in contact with a cool surface,
it condenses and drops of water appear
on the cooled surfaces. The presence of
water vapour in air is important for the
water cycle in nature.
Oxygen
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
©NCERT
not to be republished
149 AIR AROUND US
taller than the other) as shown in Fig.
15.6. 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?
The burning of the candle must be
due to presence of some component of
air, isn’t it? Do you find any difference
in your observation with the two glasses
of different heights? What can be the
reason for this?
Burning can occur only in the
presence of oxygen. We see that, one
component of air is oxygen. Now, the
amount of air and hence its oxygen
component inside each glass in our
experiment, is limited. When most of
this oxygen is used up by the burning
candle, it can no longer burn and blows
out. Also, some of the space occupied
by the oxygen inside the glass becomes
empty and the water rises up to fill or
occupy this space.
Nitrogen
In Activity 3 did you observe that a
major part of air is still present in the
glass bottle even after the candle blew
out? This indicates the presence of some
component in the air, which does not
support burning. The major part of air
(which does not support burning candle)
is nitrogen. It takes up nearly four-fifth
of the space that air fills.
Carbon dioxide
In a closed room, if there is some
material that is burning, you may
have felt suffocation. This is due to
excess of carbon dioxide that may be
accumulating in the room, as the
burning continues. Carbon dioxide
makes up a small component of the air
around us. Plants and animals consume
oxygen for respiration and produce
carbon dioxide. Plant and animal matter
on burning, also consumes oxygen and
produces mainly carbon dioxide and a
few other gases.
Dust and smoke
The burning of fuel also produces
smoke. Smoke contains a few gases and
fine dust particles and is often harmful.
That is why you see long chimneys in
factories. This takes the harmful smoke
and gases away from our noses, but,
brings it closer to the birds flying up in
the sky!
Dust particles are always present
in air.
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
Fig. 15.6 Air has oxygen
©NCERT
not to be republished
Page 4


15
Air Around us
W
e have learnt in Chapter 9 that
all living things require air.
But, have you ever seen air?
You might not have seen air, but, surely
you must have felt its presence in so
many ways. You notice it when the
leaves of the trees rustle or the clothes
hanging on a clothes-line sway. Pages
of an open book begin fluttering
when the fan is switched on. The moving
air makes it possible for you to fly your
kite. Do you remember Activity 3 in
Chapter 5 in which you separated the
sand and sawdust by winnowing?
Winnowing is more effective in moving
air. You may have noticed that during
storms the wind blows at a very high
speed. It may even uproot trees and blow
off the rooftops.
Have you ever played with a firki
(Fig. 15.1)?
Move it a little, back and
forth. Observe, what happens.
Does the firki rotate? What makes a firki
rotate — moving air, isn’t it?
Have you seen a weather cock
(Fig. 15.3)? It shows the direction in
which the air is moving at that place.
Fig. 15.1 Different types of  firki
Fig. 15.2 Making a simple firki
Fig. 15.3 A weather cock
Activity 1
Let us make a firki of our own, following
the instructions shown in Fig. 15.2.
Hold the stick of the firki and place it
in different directions in an open area.
15.1 IS AIR PRESENT EVERYWHERE
AROUND US?
Close your fist — what do you have in
it? Nothing? Try the following activity
to find out.
Activity 2
Take an empty glass bottle. Is it really
empty or does it have something inside?
Turn it, upside down. Is something
inside it, now?
©NCERT
not to be republished
148 SCIENCE
Now, dip the open mouth of the bottle
into the bucket filled with water as
shown in Fig. 15.4. Observe the bottle.
Does water enter the bottle? Now tilt the
bottle slightly. Does the water now enter
the bottle? Do you see bubbles coming
out of the bottle or hear any bubbly
sound? Can you now guess what was
in the bottle?
Yes! You are right. It is “air”, that was
present in the bottle. The bottle was not
empty at all. In fact, it was filled
completely with air even when you
turned it upside down. That is why you
notice that water does not enter the
bottle when it is in an inverted position,
as there was no space for air to escape.
When the bottle was tilted, the air was
able to come out in the form of bubbles,
and  water filled up the empty space that
the air has occupied.
This activity shows that air occupies
space. It fills all the space in the bottle.
It is present everywhere around us. Air
has no colour and one can see through
it. It is transparent.
Our earth is surrounded by a thin
layer of air. This layer extends up to
many kilometres above the surface of
the earth and is called atmosphere.
Why do you think, mountaineers
carry oxygen cylinders with them, while
climbing high mountains (Fig. 15.5)?
Fig. 15.4 Experiments with an empty bottle.
Fig. 15.5 Mountaineers carry oxygen cylinders
with them
15.2 WHAT IS AIR MADE UP OF?
Until the eighteenth century, people
thought that air was just one substance.
Experiments have proved that it is really
not so. Air is a mixture of many gases.
What kind of a mixture is it? Let us find
out about some of the major
components of this mixture, one by one.
Water vapour
We have learnt earlier that air contains
water vapour. We also saw that, when
air comes in contact with a cool surface,
it condenses and drops of water appear
on the cooled surfaces. The presence of
water vapour in air is important for the
water cycle in nature.
Oxygen
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
©NCERT
not to be republished
149 AIR AROUND US
taller than the other) as shown in Fig.
15.6. 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?
The burning of the candle must be
due to presence of some component of
air, isn’t it? Do you find any difference
in your observation with the two glasses
of different heights? What can be the
reason for this?
Burning can occur only in the
presence of oxygen. We see that, one
component of air is oxygen. Now, the
amount of air and hence its oxygen
component inside each glass in our
experiment, is limited. When most of
this oxygen is used up by the burning
candle, it can no longer burn and blows
out. Also, some of the space occupied
by the oxygen inside the glass becomes
empty and the water rises up to fill or
occupy this space.
Nitrogen
In Activity 3 did you observe that a
major part of air is still present in the
glass bottle even after the candle blew
out? This indicates the presence of some
component in the air, which does not
support burning. The major part of air
(which does not support burning candle)
is nitrogen. It takes up nearly four-fifth
of the space that air fills.
Carbon dioxide
In a closed room, if there is some
material that is burning, you may
have felt suffocation. This is due to
excess of carbon dioxide that may be
accumulating in the room, as the
burning continues. Carbon dioxide
makes up a small component of the air
around us. Plants and animals consume
oxygen for respiration and produce
carbon dioxide. Plant and animal matter
on burning, also consumes oxygen and
produces mainly carbon dioxide and a
few other gases.
Dust and smoke
The burning of fuel also produces
smoke. Smoke contains a few gases and
fine dust particles and is often harmful.
That is why you see long chimneys in
factories. This takes the harmful smoke
and gases away from our noses, but,
brings it closer to the birds flying up in
the sky!
Dust particles are always present
in air.
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
Fig. 15.6 Air has oxygen
©NCERT
not to be republished
150 SCIENCE
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. 15.7)? What are these particles?
During cold winters you might have
observed similar beam of sunlight filter
through the trees in which dust particles
appear to dance merrily around!
This shows that air also contains
dust particles. The presence of dust
particles in air varies from time to time,
and from place to place.
We inhale air when we breathe
through our nostrils. Fine hair and
mucus are present inside the nose to
prevent dust particles from getting into
the respiratory system.
Paheli  wants to know, why
the transparent glass of
windows, if not wiped off
regularly, appears hazy?
Fig. 15.7 Observing presence of dust in air with
sunlight
Fig.15.8 Policemen regulating traffic at a crowded
crossing often wear a mask
Boojho wants to know, why
during an incident of
fire, one is advised to
wrap a woollen blanket
over a burning object.
Boojho is asking you, why
do you think, the policeman
in Fig. 15.8 is wearing a
mask?
Do you recall being scolded by your
parents when you breathe through your
mouth? If you do that, harmful dust
particles may enter your body.
We may conclude, then, that air
contains some gases, water vapour and
dust particles. The gases in air are
mainly nitrogen, oxygen, small amount
of carbon dioxide, and many other
gases. However, there may be some
variations in the composition of air from
place to place. We see that air contains
©NCERT
not to be republished
Page 5


15
Air Around us
W
e have learnt in Chapter 9 that
all living things require air.
But, have you ever seen air?
You might not have seen air, but, surely
you must have felt its presence in so
many ways. You notice it when the
leaves of the trees rustle or the clothes
hanging on a clothes-line sway. Pages
of an open book begin fluttering
when the fan is switched on. The moving
air makes it possible for you to fly your
kite. Do you remember Activity 3 in
Chapter 5 in which you separated the
sand and sawdust by winnowing?
Winnowing is more effective in moving
air. You may have noticed that during
storms the wind blows at a very high
speed. It may even uproot trees and blow
off the rooftops.
Have you ever played with a firki
(Fig. 15.1)?
Move it a little, back and
forth. Observe, what happens.
Does the firki rotate? What makes a firki
rotate — moving air, isn’t it?
Have you seen a weather cock
(Fig. 15.3)? It shows the direction in
which the air is moving at that place.
Fig. 15.1 Different types of  firki
Fig. 15.2 Making a simple firki
Fig. 15.3 A weather cock
Activity 1
Let us make a firki of our own, following
the instructions shown in Fig. 15.2.
Hold the stick of the firki and place it
in different directions in an open area.
15.1 IS AIR PRESENT EVERYWHERE
AROUND US?
Close your fist — what do you have in
it? Nothing? Try the following activity
to find out.
Activity 2
Take an empty glass bottle. Is it really
empty or does it have something inside?
Turn it, upside down. Is something
inside it, now?
©NCERT
not to be republished
148 SCIENCE
Now, dip the open mouth of the bottle
into the bucket filled with water as
shown in Fig. 15.4. Observe the bottle.
Does water enter the bottle? Now tilt the
bottle slightly. Does the water now enter
the bottle? Do you see bubbles coming
out of the bottle or hear any bubbly
sound? Can you now guess what was
in the bottle?
Yes! You are right. It is “air”, that was
present in the bottle. The bottle was not
empty at all. In fact, it was filled
completely with air even when you
turned it upside down. That is why you
notice that water does not enter the
bottle when it is in an inverted position,
as there was no space for air to escape.
When the bottle was tilted, the air was
able to come out in the form of bubbles,
and  water filled up the empty space that
the air has occupied.
This activity shows that air occupies
space. It fills all the space in the bottle.
It is present everywhere around us. Air
has no colour and one can see through
it. It is transparent.
Our earth is surrounded by a thin
layer of air. This layer extends up to
many kilometres above the surface of
the earth and is called atmosphere.
Why do you think, mountaineers
carry oxygen cylinders with them, while
climbing high mountains (Fig. 15.5)?
Fig. 15.4 Experiments with an empty bottle.
Fig. 15.5 Mountaineers carry oxygen cylinders
with them
15.2 WHAT IS AIR MADE UP OF?
Until the eighteenth century, people
thought that air was just one substance.
Experiments have proved that it is really
not so. Air is a mixture of many gases.
What kind of a mixture is it? Let us find
out about some of the major
components of this mixture, one by one.
Water vapour
We have learnt earlier that air contains
water vapour. We also saw that, when
air comes in contact with a cool surface,
it condenses and drops of water appear
on the cooled surfaces. The presence of
water vapour in air is important for the
water cycle in nature.
Oxygen
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
©NCERT
not to be republished
149 AIR AROUND US
taller than the other) as shown in Fig.
15.6. 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?
The burning of the candle must be
due to presence of some component of
air, isn’t it? Do you find any difference
in your observation with the two glasses
of different heights? What can be the
reason for this?
Burning can occur only in the
presence of oxygen. We see that, one
component of air is oxygen. Now, the
amount of air and hence its oxygen
component inside each glass in our
experiment, is limited. When most of
this oxygen is used up by the burning
candle, it can no longer burn and blows
out. Also, some of the space occupied
by the oxygen inside the glass becomes
empty and the water rises up to fill or
occupy this space.
Nitrogen
In Activity 3 did you observe that a
major part of air is still present in the
glass bottle even after the candle blew
out? This indicates the presence of some
component in the air, which does not
support burning. The major part of air
(which does not support burning candle)
is nitrogen. It takes up nearly four-fifth
of the space that air fills.
Carbon dioxide
In a closed room, if there is some
material that is burning, you may
have felt suffocation. This is due to
excess of carbon dioxide that may be
accumulating in the room, as the
burning continues. Carbon dioxide
makes up a small component of the air
around us. Plants and animals consume
oxygen for respiration and produce
carbon dioxide. Plant and animal matter
on burning, also consumes oxygen and
produces mainly carbon dioxide and a
few other gases.
Dust and smoke
The burning of fuel also produces
smoke. Smoke contains a few gases and
fine dust particles and is often harmful.
That is why you see long chimneys in
factories. This takes the harmful smoke
and gases away from our noses, but,
brings it closer to the birds flying up in
the sky!
Dust particles are always present
in air.
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
Fig. 15.6 Air has oxygen
©NCERT
not to be republished
150 SCIENCE
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. 15.7)? What are these particles?
During cold winters you might have
observed similar beam of sunlight filter
through the trees in which dust particles
appear to dance merrily around!
This shows that air also contains
dust particles. The presence of dust
particles in air varies from time to time,
and from place to place.
We inhale air when we breathe
through our nostrils. Fine hair and
mucus are present inside the nose to
prevent dust particles from getting into
the respiratory system.
Paheli  wants to know, why
the transparent glass of
windows, if not wiped off
regularly, appears hazy?
Fig. 15.7 Observing presence of dust in air with
sunlight
Fig.15.8 Policemen regulating traffic at a crowded
crossing often wear a mask
Boojho wants to know, why
during an incident of
fire, one is advised to
wrap a woollen blanket
over a burning object.
Boojho is asking you, why
do you think, the policeman
in Fig. 15.8 is wearing a
mask?
Do you recall being scolded by your
parents when you breathe through your
mouth? If you do that, harmful dust
particles may enter your body.
We may conclude, then, that air
contains some gases, water vapour and
dust particles. The gases in air are
mainly nitrogen, oxygen, small amount
of carbon dioxide, and many other
gases. However, there may be some
variations in the composition of air from
place to place. We see that air contains
©NCERT
not to be republished
151 AIR AROUND US
vessel. Do you see tiny bubbles  on the
inside (Fig. 15.10)?
These bubbles come from the air
dissolved in water. When you heat the
water, to begin with, the air dissolved in
it escapes. As you continue heating, the
water itself turns into vapour and finally
begins to boil. We learnt in Chapters 8
and 9, that the animals living in water
use the dissolved oxygen in water.
The organisms that live in soil also
need oxygen to respire, isn’t it? How do
they get the air they need, for
respiration?
Activity 6
Take a lump of dry soil in a beaker or a
glass. Add water to it and note what
happens (Fig. 15.11). Do you see
bubbles coming out from soil? These
bubbles indicate the presence of air in
the soil.
When the water is poured on the
lump of soil, it displaces the air which
is seen in the form of bubbles. The
organisms that live inside the soil and
the plant roots respire in this air. A lot Fig. 15.10 Water contains air!
mostly nitrogen and oxygen. In fact,
these two gases together make up 99%
of the air. The remaining 1% is
constituted by carbon dioxide and a few
other gases, water vapour and dust
particles (Fig. 15.9).
15.3 HOW DOES OXYGEN BECOME
AVAILABLE TO ANIMALS AND PLANTS
LIVING IN WATER AND SOIL?
Activity 5
Take some water in a glass vessel or
beaker. Heat it slowly on a tripod stand.
Well before the water begins to boil, look
carefully at the inner surface of the
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.
Nitrogen
oxygen
carbon dioxide,
water vapour
and other gases
Fig.15.9 Composition of air
©NCERT
not to be republished
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