Selina Textbook Solutions: Water | Chemistry Class 9 ICSE PDF Download

 Page 1


Water 
Exercise 6(A) 
Solution 1. 
In free state, water occurs in three states viz, solid, liquid and gaseous state. 
1. Solid state of water: In solid state, a large amount of fresh water is found in the 
form of snow or Ice. 
2. Liquid state of water: Most of the water present in oceans, on land water found in 
streams, rivers, lakes, ponds, springs are also liquid state of water. 
3. Gaseous state of water: In gaseous form, water vapours present in air. When 
these vapours condense, they form clouds, mist, fog etc. are examples of water in 
gaseous form. 
Solution 2. 
Water is considered as a compound because it is made up of two elements, hydrogen 
and oxygen combined in the ratio of 1 : 8 by mass. 
Mass ratio of elements H 2O 
H : O, 2 X 1 : 16 X 1 = 1 : 8 
(Atomic mass of H = 1, O = 16) 
And also components of water cannot be separated by physical methods but can be 
separated by electrolysis of water. 
Solution 3. 
(a) The temperature in Mumbai and Chennai do not fall as low as in Delhi because 
Mumbai and Chennai are situated at the bank of the oceans due to high specific heat 
capacity the presence of a large amount of water is able to modify the climate of the 
nearby land areas are warmer in winter and cooler in summer temperature does not fall 
wherever Delhi has not same condition. 
(b) Our body is almost 65% of water and water has property of specific heat. Due high 
specific heat capacity the presence of large amount of water is able to modify the 
climate of the body and control the temperature of our body which is warm in winter and 
cooler in summer. 
 
Page 2


Water 
Exercise 6(A) 
Solution 1. 
In free state, water occurs in three states viz, solid, liquid and gaseous state. 
1. Solid state of water: In solid state, a large amount of fresh water is found in the 
form of snow or Ice. 
2. Liquid state of water: Most of the water present in oceans, on land water found in 
streams, rivers, lakes, ponds, springs are also liquid state of water. 
3. Gaseous state of water: In gaseous form, water vapours present in air. When 
these vapours condense, they form clouds, mist, fog etc. are examples of water in 
gaseous form. 
Solution 2. 
Water is considered as a compound because it is made up of two elements, hydrogen 
and oxygen combined in the ratio of 1 : 8 by mass. 
Mass ratio of elements H 2O 
H : O, 2 X 1 : 16 X 1 = 1 : 8 
(Atomic mass of H = 1, O = 16) 
And also components of water cannot be separated by physical methods but can be 
separated by electrolysis of water. 
Solution 3. 
(a) The temperature in Mumbai and Chennai do not fall as low as in Delhi because 
Mumbai and Chennai are situated at the bank of the oceans due to high specific heat 
capacity the presence of a large amount of water is able to modify the climate of the 
nearby land areas are warmer in winter and cooler in summer temperature does not fall 
wherever Delhi has not same condition. 
(b) Our body is almost 65% of water and water has property of specific heat. Due high 
specific heat capacity the presence of large amount of water is able to modify the 
climate of the body and control the temperature of our body which is warm in winter and 
cooler in summer. 
 
Solution 4. 
Water dissolves many substances forming aqueous solution. It can dissolve solids, 
liquids and gases. When a solid dissolves in water the solid is said to be solute, the 
water (the solvent) and the resultant liquid, the solution. So it is said that water is a 
universal solvent. In other words water can dissolve nearly every substance. 
Solution 5. 
The sudden release of the latent heat of condensation causes the violence associated 
with torrential rain. 
Solution 6. 
(a) Specific heat 
(b) Water has an unusual physical property. When cooled, it first contracts in volume, as 
do other liquids, but at 4°C (maximum density), it starts expanding, and continues to do 
so till the temperature reaches 0°C, the point at which it freezes into ice. 
The property of anomalous expansion of water enables marine life to exist in the colder 
regions of the world, because even when the water freezes on the top, it is still liquid 
below the ice layer. 
 
(C) Melting point: The constant temperature at which a solid changes into a liquid 
state, by absorbing the heat energy is called melting point. 
Page 3


Water 
Exercise 6(A) 
Solution 1. 
In free state, water occurs in three states viz, solid, liquid and gaseous state. 
1. Solid state of water: In solid state, a large amount of fresh water is found in the 
form of snow or Ice. 
2. Liquid state of water: Most of the water present in oceans, on land water found in 
streams, rivers, lakes, ponds, springs are also liquid state of water. 
3. Gaseous state of water: In gaseous form, water vapours present in air. When 
these vapours condense, they form clouds, mist, fog etc. are examples of water in 
gaseous form. 
Solution 2. 
Water is considered as a compound because it is made up of two elements, hydrogen 
and oxygen combined in the ratio of 1 : 8 by mass. 
Mass ratio of elements H 2O 
H : O, 2 X 1 : 16 X 1 = 1 : 8 
(Atomic mass of H = 1, O = 16) 
And also components of water cannot be separated by physical methods but can be 
separated by electrolysis of water. 
Solution 3. 
(a) The temperature in Mumbai and Chennai do not fall as low as in Delhi because 
Mumbai and Chennai are situated at the bank of the oceans due to high specific heat 
capacity the presence of a large amount of water is able to modify the climate of the 
nearby land areas are warmer in winter and cooler in summer temperature does not fall 
wherever Delhi has not same condition. 
(b) Our body is almost 65% of water and water has property of specific heat. Due high 
specific heat capacity the presence of large amount of water is able to modify the 
climate of the body and control the temperature of our body which is warm in winter and 
cooler in summer. 
 
Solution 4. 
Water dissolves many substances forming aqueous solution. It can dissolve solids, 
liquids and gases. When a solid dissolves in water the solid is said to be solute, the 
water (the solvent) and the resultant liquid, the solution. So it is said that water is a 
universal solvent. In other words water can dissolve nearly every substance. 
Solution 5. 
The sudden release of the latent heat of condensation causes the violence associated 
with torrential rain. 
Solution 6. 
(a) Specific heat 
(b) Water has an unusual physical property. When cooled, it first contracts in volume, as 
do other liquids, but at 4°C (maximum density), it starts expanding, and continues to do 
so till the temperature reaches 0°C, the point at which it freezes into ice. 
The property of anomalous expansion of water enables marine life to exist in the colder 
regions of the world, because even when the water freezes on the top, it is still liquid 
below the ice layer. 
 
(C) Melting point: The constant temperature at which a solid changes into a liquid 
state, by absorbing the heat energy is called melting point. 
Boiling point: The temperature at which water starts boiling under normal pressure is 
called boiling point of water.” It is 100°C. Boiling point increases with increase in 
pressure and vice versa.” 
Specific heat capacity: The amount of heat required to raise the temperature of unit 
mass of that substance through 1°C. 
Latent heat of vaporization of water: The energy required to change water into 
its vapour at its boiling point without any change in temperature is called latent heat of 
vaporization of water. 
Latent heat of vaporization of water is 2260 joules J/g or 540 cal/g. 
In the reverse process, 2260 joules of heat is released when 1 g of steam condenses to 
form 1 g of water at 100°C. 
Latent heat of fusion of ice: The amount of heat energy required by ice to change into 
water is called latent heat of fusion of ice. 
Latent heat of fusion of ice is 336 J/g or 80 cal/g. 
In the reverse process, 336 joules of heat is released when 1 g of water solidifies to 
form 1 g of ice at 0°C. 
Solution 7. 
Composition of water :- Hydrogen and Oxygen Volume Ratio = H 2 : O 
= 2 : 1 
Solution 8. 
The properties of water are different from the properties of elements from which it 
is formed 
Property Water Elements – Oxygen and Hydrogen 
Nature It is clear, colourless, odourless, tasteless 
and transparent liquid. 
These are colourless,odourless, 
tasteless and non-poisonous gases. 
Solubility It can dissolve many things in it and is 
called universal solvent. 
Oxygen and hydrogen are slightly 
soluble in water. 
Density Pure water has maximum density at 4°C. Oxygen is heavier than air wherever is 
the lightest of all the known gases. 
Solution 9. 
The property of anomalous expansion of water enables aquatic life to exist because of 
the water freezes on top of the surface of the water body, but it is still liquid below the 
ice layer. 
Page 4


Water 
Exercise 6(A) 
Solution 1. 
In free state, water occurs in three states viz, solid, liquid and gaseous state. 
1. Solid state of water: In solid state, a large amount of fresh water is found in the 
form of snow or Ice. 
2. Liquid state of water: Most of the water present in oceans, on land water found in 
streams, rivers, lakes, ponds, springs are also liquid state of water. 
3. Gaseous state of water: In gaseous form, water vapours present in air. When 
these vapours condense, they form clouds, mist, fog etc. are examples of water in 
gaseous form. 
Solution 2. 
Water is considered as a compound because it is made up of two elements, hydrogen 
and oxygen combined in the ratio of 1 : 8 by mass. 
Mass ratio of elements H 2O 
H : O, 2 X 1 : 16 X 1 = 1 : 8 
(Atomic mass of H = 1, O = 16) 
And also components of water cannot be separated by physical methods but can be 
separated by electrolysis of water. 
Solution 3. 
(a) The temperature in Mumbai and Chennai do not fall as low as in Delhi because 
Mumbai and Chennai are situated at the bank of the oceans due to high specific heat 
capacity the presence of a large amount of water is able to modify the climate of the 
nearby land areas are warmer in winter and cooler in summer temperature does not fall 
wherever Delhi has not same condition. 
(b) Our body is almost 65% of water and water has property of specific heat. Due high 
specific heat capacity the presence of large amount of water is able to modify the 
climate of the body and control the temperature of our body which is warm in winter and 
cooler in summer. 
 
Solution 4. 
Water dissolves many substances forming aqueous solution. It can dissolve solids, 
liquids and gases. When a solid dissolves in water the solid is said to be solute, the 
water (the solvent) and the resultant liquid, the solution. So it is said that water is a 
universal solvent. In other words water can dissolve nearly every substance. 
Solution 5. 
The sudden release of the latent heat of condensation causes the violence associated 
with torrential rain. 
Solution 6. 
(a) Specific heat 
(b) Water has an unusual physical property. When cooled, it first contracts in volume, as 
do other liquids, but at 4°C (maximum density), it starts expanding, and continues to do 
so till the temperature reaches 0°C, the point at which it freezes into ice. 
The property of anomalous expansion of water enables marine life to exist in the colder 
regions of the world, because even when the water freezes on the top, it is still liquid 
below the ice layer. 
 
(C) Melting point: The constant temperature at which a solid changes into a liquid 
state, by absorbing the heat energy is called melting point. 
Boiling point: The temperature at which water starts boiling under normal pressure is 
called boiling point of water.” It is 100°C. Boiling point increases with increase in 
pressure and vice versa.” 
Specific heat capacity: The amount of heat required to raise the temperature of unit 
mass of that substance through 1°C. 
Latent heat of vaporization of water: The energy required to change water into 
its vapour at its boiling point without any change in temperature is called latent heat of 
vaporization of water. 
Latent heat of vaporization of water is 2260 joules J/g or 540 cal/g. 
In the reverse process, 2260 joules of heat is released when 1 g of steam condenses to 
form 1 g of water at 100°C. 
Latent heat of fusion of ice: The amount of heat energy required by ice to change into 
water is called latent heat of fusion of ice. 
Latent heat of fusion of ice is 336 J/g or 80 cal/g. 
In the reverse process, 336 joules of heat is released when 1 g of water solidifies to 
form 1 g of ice at 0°C. 
Solution 7. 
Composition of water :- Hydrogen and Oxygen Volume Ratio = H 2 : O 
= 2 : 1 
Solution 8. 
The properties of water are different from the properties of elements from which it 
is formed 
Property Water Elements – Oxygen and Hydrogen 
Nature It is clear, colourless, odourless, tasteless 
and transparent liquid. 
These are colourless,odourless, 
tasteless and non-poisonous gases. 
Solubility It can dissolve many things in it and is 
called universal solvent. 
Oxygen and hydrogen are slightly 
soluble in water. 
Density Pure water has maximum density at 4°C. Oxygen is heavier than air wherever is 
the lightest of all the known gases. 
Solution 9. 
The property of anomalous expansion of water enables aquatic life to exist because of 
the water freezes on top of the surface of the water body, but it is still liquid below the 
ice layer. 
Solution 10. 
(a) Aim: To show that tap water contains dissolved salts. 
Procedure: Put some tap water on a clean watch glass and place it over a beaker 
containing water as shown in fig. Boil the water in the beaker. When all the water has 
evaporated from the watch glass, remove the burner and let it cool. We see at the watch 
glass against light, a number of concentric rings of solids matter on it. These are 
dissolved impurities, left behind after evaporation of water. To show that water contains 
dissolved solids. 
 
(b) Aim: To show that tap water contains dissolved gases. 
Procedure: Take a round bottomed flask and filled it with the tap water. In its mouth fix 
a delivery tube, in such a way that its lower end of the delivery tube is in line with the 
under – surface of the cork. 
Arrange the apparatus according to diagram. 
Heat the flask with the help of a Bunsen burner. It is seen that tiny bubbles of gas are 
coming out, which stick to the sides of flask, heat it continuously, till the water is about 
to boil. It is seen that Bubbles of gas start coming out of beehive shelf. 
Now lower the flame, to keep the water just near its boiling point. Invert over the 
beehive shelf a graduated tube, completely filled with tap water. Gradually, the boiled off 
air, starts collecting in the flask. Collect at least two tubes of boiled off air. 
Page 5


Water 
Exercise 6(A) 
Solution 1. 
In free state, water occurs in three states viz, solid, liquid and gaseous state. 
1. Solid state of water: In solid state, a large amount of fresh water is found in the 
form of snow or Ice. 
2. Liquid state of water: Most of the water present in oceans, on land water found in 
streams, rivers, lakes, ponds, springs are also liquid state of water. 
3. Gaseous state of water: In gaseous form, water vapours present in air. When 
these vapours condense, they form clouds, mist, fog etc. are examples of water in 
gaseous form. 
Solution 2. 
Water is considered as a compound because it is made up of two elements, hydrogen 
and oxygen combined in the ratio of 1 : 8 by mass. 
Mass ratio of elements H 2O 
H : O, 2 X 1 : 16 X 1 = 1 : 8 
(Atomic mass of H = 1, O = 16) 
And also components of water cannot be separated by physical methods but can be 
separated by electrolysis of water. 
Solution 3. 
(a) The temperature in Mumbai and Chennai do not fall as low as in Delhi because 
Mumbai and Chennai are situated at the bank of the oceans due to high specific heat 
capacity the presence of a large amount of water is able to modify the climate of the 
nearby land areas are warmer in winter and cooler in summer temperature does not fall 
wherever Delhi has not same condition. 
(b) Our body is almost 65% of water and water has property of specific heat. Due high 
specific heat capacity the presence of large amount of water is able to modify the 
climate of the body and control the temperature of our body which is warm in winter and 
cooler in summer. 
 
Solution 4. 
Water dissolves many substances forming aqueous solution. It can dissolve solids, 
liquids and gases. When a solid dissolves in water the solid is said to be solute, the 
water (the solvent) and the resultant liquid, the solution. So it is said that water is a 
universal solvent. In other words water can dissolve nearly every substance. 
Solution 5. 
The sudden release of the latent heat of condensation causes the violence associated 
with torrential rain. 
Solution 6. 
(a) Specific heat 
(b) Water has an unusual physical property. When cooled, it first contracts in volume, as 
do other liquids, but at 4°C (maximum density), it starts expanding, and continues to do 
so till the temperature reaches 0°C, the point at which it freezes into ice. 
The property of anomalous expansion of water enables marine life to exist in the colder 
regions of the world, because even when the water freezes on the top, it is still liquid 
below the ice layer. 
 
(C) Melting point: The constant temperature at which a solid changes into a liquid 
state, by absorbing the heat energy is called melting point. 
Boiling point: The temperature at which water starts boiling under normal pressure is 
called boiling point of water.” It is 100°C. Boiling point increases with increase in 
pressure and vice versa.” 
Specific heat capacity: The amount of heat required to raise the temperature of unit 
mass of that substance through 1°C. 
Latent heat of vaporization of water: The energy required to change water into 
its vapour at its boiling point without any change in temperature is called latent heat of 
vaporization of water. 
Latent heat of vaporization of water is 2260 joules J/g or 540 cal/g. 
In the reverse process, 2260 joules of heat is released when 1 g of steam condenses to 
form 1 g of water at 100°C. 
Latent heat of fusion of ice: The amount of heat energy required by ice to change into 
water is called latent heat of fusion of ice. 
Latent heat of fusion of ice is 336 J/g or 80 cal/g. 
In the reverse process, 336 joules of heat is released when 1 g of water solidifies to 
form 1 g of ice at 0°C. 
Solution 7. 
Composition of water :- Hydrogen and Oxygen Volume Ratio = H 2 : O 
= 2 : 1 
Solution 8. 
The properties of water are different from the properties of elements from which it 
is formed 
Property Water Elements – Oxygen and Hydrogen 
Nature It is clear, colourless, odourless, tasteless 
and transparent liquid. 
These are colourless,odourless, 
tasteless and non-poisonous gases. 
Solubility It can dissolve many things in it and is 
called universal solvent. 
Oxygen and hydrogen are slightly 
soluble in water. 
Density Pure water has maximum density at 4°C. Oxygen is heavier than air wherever is 
the lightest of all the known gases. 
Solution 9. 
The property of anomalous expansion of water enables aquatic life to exist because of 
the water freezes on top of the surface of the water body, but it is still liquid below the 
ice layer. 
Solution 10. 
(a) Aim: To show that tap water contains dissolved salts. 
Procedure: Put some tap water on a clean watch glass and place it over a beaker 
containing water as shown in fig. Boil the water in the beaker. When all the water has 
evaporated from the watch glass, remove the burner and let it cool. We see at the watch 
glass against light, a number of concentric rings of solids matter on it. These are 
dissolved impurities, left behind after evaporation of water. To show that water contains 
dissolved solids. 
 
(b) Aim: To show that tap water contains dissolved gases. 
Procedure: Take a round bottomed flask and filled it with the tap water. In its mouth fix 
a delivery tube, in such a way that its lower end of the delivery tube is in line with the 
under – surface of the cork. 
Arrange the apparatus according to diagram. 
Heat the flask with the help of a Bunsen burner. It is seen that tiny bubbles of gas are 
coming out, which stick to the sides of flask, heat it continuously, till the water is about 
to boil. It is seen that Bubbles of gas start coming out of beehive shelf. 
Now lower the flame, to keep the water just near its boiling point. Invert over the 
beehive shelf a graduated tube, completely filled with tap water. Gradually, the boiled off 
air, starts collecting in the flask. Collect at least two tubes of boiled off air. 
 
Solution 11. 
CO 2 and O 2 add taste to water for drinking purposes. 
Solution 12. 
Oxygen is more soluble in water than nitrogen. Air dissolved in water contains a higher 
percentage of oxygen. That is, 30% – 35% and in ordinary air it is only 21 %. In this way 
air dissolved in water is different from ordinary air. 
Solution 13. 
Rivers and lakes have large amount of water and water has high specific heat capacity, 
due to which they do not freeze easily. 
Even if they freeze, they freeze at top layer. There is water below due to Anomalous 
expansion of water. 
Solution 14. 
Importance of dissolved salts in water: 
1. Dissolved salts provide a specific taste to water. 
2. Dissolved salts act as micro-nutrients for the growth and development of living 
beings.