NCERT Textbook: Water | Social Studies (SST) Class 7 PDF Download

 Page 1


Glossary
Fig. 5.1: Water Cycle
Condensation
Precipitation
Run off
Evaporation
5
Water
When you think of water, what images come to your
mind? You think of rivers, the waterfalls, the pitter patter
of raindrops, water in your taps... Children love to float
paper boats in rain puddles. By noon the puddles vanish.
Where does the water go?
The sun’s heat causes evaporation of water into
vapour. When the water vapour cools down, it condenses
and forms clouds. From there it may fall on the land or
sea in the form of rain, snow or sleet.
The process by which water continually changes its
form and circulates between oceans,
atmosphere and land is known
as the water cycle (Fig 5.1).
Our earth is like a
terrarium. The same water
that existed centuries ago
still exists today. The
water used to irrigate a
field in Haryana may
have flowed down the
Amazon River a
hundred years ago.
The major sources
of fresh water are the
rivers, ponds,
springs and
glaciers. The
ocean bodies and
the seas contain
salty water. The
water of the
oceans is salty or
saline as it
contains large
Terrarium: It is an
artificial enclosure for
keeping small house
plants.
Activity
Fill one-fourth of a big
jar with soil and
press it well. Put a
thin layer of humus
on top of it. Plant the
largest plants first
and then arrange the
smaller ones around
them. Spray the
arrangement with
water and close the
jar. The water that
evaporates from the
leaves and soil
condenses and falls
back in the form of
drops of water.
A Terrarium
Make your own
Terrarium
Reprint 2024-25
Page 2


Glossary
Fig. 5.1: Water Cycle
Condensation
Precipitation
Run off
Evaporation
5
Water
When you think of water, what images come to your
mind? You think of rivers, the waterfalls, the pitter patter
of raindrops, water in your taps... Children love to float
paper boats in rain puddles. By noon the puddles vanish.
Where does the water go?
The sun’s heat causes evaporation of water into
vapour. When the water vapour cools down, it condenses
and forms clouds. From there it may fall on the land or
sea in the form of rain, snow or sleet.
The process by which water continually changes its
form and circulates between oceans,
atmosphere and land is known
as the water cycle (Fig 5.1).
Our earth is like a
terrarium. The same water
that existed centuries ago
still exists today. The
water used to irrigate a
field in Haryana may
have flowed down the
Amazon River a
hundred years ago.
The major sources
of fresh water are the
rivers, ponds,
springs and
glaciers. The
ocean bodies and
the seas contain
salty water. The
water of the
oceans is salty or
saline as it
contains large
Terrarium: It is an
artificial enclosure for
keeping small house
plants.
Activity
Fill one-fourth of a big
jar with soil and
press it well. Put a
thin layer of humus
on top of it. Plant the
largest plants first
and then arrange the
smaller ones around
them. Spray the
arrangement with
water and close the
jar. The water that
evaporates from the
leaves and soil
condenses and falls
back in the form of
drops of water.
A Terrarium
Make your own
Terrarium
Reprint 2024-25
Fig. 5.2: World – Major Seas, Lakes and Rivers
WATER 31
amount of dissolved salts. Most of the salt is sodium
chloride or the common table salt that you eat.
Reprint 2024-25
Page 3


Glossary
Fig. 5.1: Water Cycle
Condensation
Precipitation
Run off
Evaporation
5
Water
When you think of water, what images come to your
mind? You think of rivers, the waterfalls, the pitter patter
of raindrops, water in your taps... Children love to float
paper boats in rain puddles. By noon the puddles vanish.
Where does the water go?
The sun’s heat causes evaporation of water into
vapour. When the water vapour cools down, it condenses
and forms clouds. From there it may fall on the land or
sea in the form of rain, snow or sleet.
The process by which water continually changes its
form and circulates between oceans,
atmosphere and land is known
as the water cycle (Fig 5.1).
Our earth is like a
terrarium. The same water
that existed centuries ago
still exists today. The
water used to irrigate a
field in Haryana may
have flowed down the
Amazon River a
hundred years ago.
The major sources
of fresh water are the
rivers, ponds,
springs and
glaciers. The
ocean bodies and
the seas contain
salty water. The
water of the
oceans is salty or
saline as it
contains large
Terrarium: It is an
artificial enclosure for
keeping small house
plants.
Activity
Fill one-fourth of a big
jar with soil and
press it well. Put a
thin layer of humus
on top of it. Plant the
largest plants first
and then arrange the
smaller ones around
them. Spray the
arrangement with
water and close the
jar. The water that
evaporates from the
leaves and soil
condenses and falls
back in the form of
drops of water.
A Terrarium
Make your own
Terrarium
Reprint 2024-25
Fig. 5.2: World – Major Seas, Lakes and Rivers
WATER 31
amount of dissolved salts. Most of the salt is sodium
chloride or the common table salt that you eat.
Reprint 2024-25
32 OUR ENVIRONMENT
Do you know?
Activity
Distribution of fresh water
1 Drop = rivers
9 Spoons =
icecaps
2 Spoons =
ground water
½ Spoons =
fresh water lakes
Take 2 litres of water. Let it represent the total
water on the surface of the earth. Measure out
12 spoons of water from this vessel into another
bowl. The water that is left behind in the vessel
represents the salty water found in oceans and
seas. This water is obviously not fit for
consuming. It is saline (contains salts).
The 12 spoons of water that was taken in a
bowl is the total amount of fresh water on earth.
The figure shows us the distribution of this fresh
water. See for yourself how much water can
actually be used by you.
Do you know?
Dead sea in Israel has
salinity of 340 grams
per litre of water.
Swimmers can float
in it because the
increased salt content
makes it dense.
Oceans : 97.3
Ice-caps : 02.0
Ground water : 0.68
Fresh water lakes : 0.009
Inland seas and
salt lakes : 0.009
Atmosphere : 0.0019
Rivers : 0.0001
100.00
Saline Water
Fresh Water
Salinity is the
amount of salt in
grams present in
1000 grams of water.
The average salinity
of the oceans is 35
parts per thousand.
DISTRIBUTION OF WATER BODIES
We all know that three-fourth of the earth surface is
covered by water. If there is more water than land on
this earth, why do so many countries face water scarcity?
Is all the water on earth available to us? The following
table gives the distribution of water in percentage.
Water distribution can be demonstrated by a simple
activity (see activity box).
Water is absolutely essential for survival. Water alone
can quench our thirst when we are thirsty. Now don’t
you think we are wasting a precious resource when we
use water carelessly?
Reprint 2024-25
Page 4


Glossary
Fig. 5.1: Water Cycle
Condensation
Precipitation
Run off
Evaporation
5
Water
When you think of water, what images come to your
mind? You think of rivers, the waterfalls, the pitter patter
of raindrops, water in your taps... Children love to float
paper boats in rain puddles. By noon the puddles vanish.
Where does the water go?
The sun’s heat causes evaporation of water into
vapour. When the water vapour cools down, it condenses
and forms clouds. From there it may fall on the land or
sea in the form of rain, snow or sleet.
The process by which water continually changes its
form and circulates between oceans,
atmosphere and land is known
as the water cycle (Fig 5.1).
Our earth is like a
terrarium. The same water
that existed centuries ago
still exists today. The
water used to irrigate a
field in Haryana may
have flowed down the
Amazon River a
hundred years ago.
The major sources
of fresh water are the
rivers, ponds,
springs and
glaciers. The
ocean bodies and
the seas contain
salty water. The
water of the
oceans is salty or
saline as it
contains large
Terrarium: It is an
artificial enclosure for
keeping small house
plants.
Activity
Fill one-fourth of a big
jar with soil and
press it well. Put a
thin layer of humus
on top of it. Plant the
largest plants first
and then arrange the
smaller ones around
them. Spray the
arrangement with
water and close the
jar. The water that
evaporates from the
leaves and soil
condenses and falls
back in the form of
drops of water.
A Terrarium
Make your own
Terrarium
Reprint 2024-25
Fig. 5.2: World – Major Seas, Lakes and Rivers
WATER 31
amount of dissolved salts. Most of the salt is sodium
chloride or the common table salt that you eat.
Reprint 2024-25
32 OUR ENVIRONMENT
Do you know?
Activity
Distribution of fresh water
1 Drop = rivers
9 Spoons =
icecaps
2 Spoons =
ground water
½ Spoons =
fresh water lakes
Take 2 litres of water. Let it represent the total
water on the surface of the earth. Measure out
12 spoons of water from this vessel into another
bowl. The water that is left behind in the vessel
represents the salty water found in oceans and
seas. This water is obviously not fit for
consuming. It is saline (contains salts).
The 12 spoons of water that was taken in a
bowl is the total amount of fresh water on earth.
The figure shows us the distribution of this fresh
water. See for yourself how much water can
actually be used by you.
Do you know?
Dead sea in Israel has
salinity of 340 grams
per litre of water.
Swimmers can float
in it because the
increased salt content
makes it dense.
Oceans : 97.3
Ice-caps : 02.0
Ground water : 0.68
Fresh water lakes : 0.009
Inland seas and
salt lakes : 0.009
Atmosphere : 0.0019
Rivers : 0.0001
100.00
Saline Water
Fresh Water
Salinity is the
amount of salt in
grams present in
1000 grams of water.
The average salinity
of the oceans is 35
parts per thousand.
DISTRIBUTION OF WATER BODIES
We all know that three-fourth of the earth surface is
covered by water. If there is more water than land on
this earth, why do so many countries face water scarcity?
Is all the water on earth available to us? The following
table gives the distribution of water in percentage.
Water distribution can be demonstrated by a simple
activity (see activity box).
Water is absolutely essential for survival. Water alone
can quench our thirst when we are thirsty. Now don’t
you think we are wasting a precious resource when we
use water carelessly?
Reprint 2024-25
WATER 33
Activity
OCEAN CIRCULATION
There is something magical about walking bare feet
on the seashore. The wet sand on the beach, the cool
breeze, the seabirds, the smell of the salt in the air
and music of the waves; everything is so fascinating.
Unlike the calm waters of ponds and lakes, ocean water
keeps moving continuously. It is never still. The
movements that occur in oceans can be broadly
categorised as: waves, tides and currents.
Do you know?
March 22
 
is
celebrated as World
Water Day when the
need to conserve
water is reinforced in
different ways.
• Why is water important for us?
• Suggest some ways in which water can be conserved (a) in your home
(b) in your school
Fig. 5.3: Pacific Ocean
Reprint 2024-25
Page 5


Glossary
Fig. 5.1: Water Cycle
Condensation
Precipitation
Run off
Evaporation
5
Water
When you think of water, what images come to your
mind? You think of rivers, the waterfalls, the pitter patter
of raindrops, water in your taps... Children love to float
paper boats in rain puddles. By noon the puddles vanish.
Where does the water go?
The sun’s heat causes evaporation of water into
vapour. When the water vapour cools down, it condenses
and forms clouds. From there it may fall on the land or
sea in the form of rain, snow or sleet.
The process by which water continually changes its
form and circulates between oceans,
atmosphere and land is known
as the water cycle (Fig 5.1).
Our earth is like a
terrarium. The same water
that existed centuries ago
still exists today. The
water used to irrigate a
field in Haryana may
have flowed down the
Amazon River a
hundred years ago.
The major sources
of fresh water are the
rivers, ponds,
springs and
glaciers. The
ocean bodies and
the seas contain
salty water. The
water of the
oceans is salty or
saline as it
contains large
Terrarium: It is an
artificial enclosure for
keeping small house
plants.
Activity
Fill one-fourth of a big
jar with soil and
press it well. Put a
thin layer of humus
on top of it. Plant the
largest plants first
and then arrange the
smaller ones around
them. Spray the
arrangement with
water and close the
jar. The water that
evaporates from the
leaves and soil
condenses and falls
back in the form of
drops of water.
A Terrarium
Make your own
Terrarium
Reprint 2024-25
Fig. 5.2: World – Major Seas, Lakes and Rivers
WATER 31
amount of dissolved salts. Most of the salt is sodium
chloride or the common table salt that you eat.
Reprint 2024-25
32 OUR ENVIRONMENT
Do you know?
Activity
Distribution of fresh water
1 Drop = rivers
9 Spoons =
icecaps
2 Spoons =
ground water
½ Spoons =
fresh water lakes
Take 2 litres of water. Let it represent the total
water on the surface of the earth. Measure out
12 spoons of water from this vessel into another
bowl. The water that is left behind in the vessel
represents the salty water found in oceans and
seas. This water is obviously not fit for
consuming. It is saline (contains salts).
The 12 spoons of water that was taken in a
bowl is the total amount of fresh water on earth.
The figure shows us the distribution of this fresh
water. See for yourself how much water can
actually be used by you.
Do you know?
Dead sea in Israel has
salinity of 340 grams
per litre of water.
Swimmers can float
in it because the
increased salt content
makes it dense.
Oceans : 97.3
Ice-caps : 02.0
Ground water : 0.68
Fresh water lakes : 0.009
Inland seas and
salt lakes : 0.009
Atmosphere : 0.0019
Rivers : 0.0001
100.00
Saline Water
Fresh Water
Salinity is the
amount of salt in
grams present in
1000 grams of water.
The average salinity
of the oceans is 35
parts per thousand.
DISTRIBUTION OF WATER BODIES
We all know that three-fourth of the earth surface is
covered by water. If there is more water than land on
this earth, why do so many countries face water scarcity?
Is all the water on earth available to us? The following
table gives the distribution of water in percentage.
Water distribution can be demonstrated by a simple
activity (see activity box).
Water is absolutely essential for survival. Water alone
can quench our thirst when we are thirsty. Now don’t
you think we are wasting a precious resource when we
use water carelessly?
Reprint 2024-25
WATER 33
Activity
OCEAN CIRCULATION
There is something magical about walking bare feet
on the seashore. The wet sand on the beach, the cool
breeze, the seabirds, the smell of the salt in the air
and music of the waves; everything is so fascinating.
Unlike the calm waters of ponds and lakes, ocean water
keeps moving continuously. It is never still. The
movements that occur in oceans can be broadly
categorised as: waves, tides and currents.
Do you know?
March 22
 
is
celebrated as World
Water Day when the
need to conserve
water is reinforced in
different ways.
• Why is water important for us?
• Suggest some ways in which water can be conserved (a) in your home
(b) in your school
Fig. 5.3: Pacific Ocean
Reprint 2024-25
34 OUR ENVIRONMENT
Waves
When you are playing throw ball on the beach and the
ball falls into the water, what happens? It is fun to watch
how the ball gets washed
back to the shore by the
waves. When the water on the
surface of the ocean rises and
falls alternately, they are
called waves.
Do you know?
Tsunami is a
Japanese word that
means “Harbour
waves” as the
harbours get
destroyed whenever
there is tsunami.
TSUNAMI – THE EARTH’S PANDEMONIUM
Tsunami or the harbour wave struck havoc in the Indian Ocean on the
26 December 2004. The wave was the result of the earthquake that had
its epicenter close to the western boundary of Sumatra. The magnitude
of the earthquake was 9.0 on the Richter scale. As the Indian plate
went under the Burma plate, there was a sudden movement of the sea
floor, causing the earthquake. The ocean floor was displaced by about
10 – 20m and tilted in a downwardly direction. A huge mass of ocean
water flowed to fill in the gap that was being created by the displacement.
This marked the withdrawal of the water mass from the coastlines of
the landmasses in the south and southeast Asia. After thrusting of the
Indian plate below the Burma plate, the water mass rushed back towards
the coastline. Tsunami travelled at a speed of about 800km. per hour,
comparable to speed of commercial aircraft and completely washed away
Do you know?
Waves are formed
when winds scrape
across the ocean
surface. The stronger
the wind blows, the
bigger the wave
becomes.
Fig. 5.4: Fig. 5.4: Fig. 5.4: Fig. 5.4: Fig. 5.4: Waves
During a storm, the winds blowing at very high speed
form huge waves. These may cause tremendous
destruction. An earthquake, a volcanic eruption or
underwater landslides can shift large amounts of ocean
water. As a result a huge tidal wave called tsunami, that
may be as high as 15m. is formed. The largest tsunami
ever measured was 150m. high. These waves travel at a
speed of more than 700 km. per hour. The tsunami of
2004 caused wide spread damage in the coastal areas of
India. The Indira point in the Andaman and Nicobar
islands got submerged after the tsunami.
Reprint 2024-25