Selina Textbook Solutions: Matter and Its Composition | Chemistry Class 9 ICSE PDF Download

 Page 1


Chapter 1. Matter and its Composition
Exercise 1
Solution 1.
(a) Melting point: The constant temperature at which a solid changes into liquid state 
by absorbing heat energy is called melting point.
(b) Boiling point: It is the temperature at which a liquid changes into vapour under 
atmospheric pressure.
(c) Evaporation: The slow passing of molecules of a liquid into gaseous state at a 
temperature below its boiling point.
(d) Freezing: It is a process in which a liquid changes into solid state by giving out heat 
energy.
Solution 2.
Boiling point of a liquid can be raised by increasing the atmospheric pressure.
Solution 3.
On heating, solid wax melts into liquid wax, which on further heating, is converted into 
wax vapours. These changes can be seen in a burning candle. The candle is made up of a 
solid wax. When we light a candle, the wax near its wick melts. The molten wax rises up 
the wick and is converted into wax vapour. The wax vapour mixes with oxygen in the air 
and burns. In a lighted candle, you can see the solid and the liquid states of wax. The 
vapour of wax can be seen rising from the wick for some time after the candle is put out. 
Solution 4.
Page 2


Chapter 1. Matter and its Composition
Exercise 1
Solution 1.
(a) Melting point: The constant temperature at which a solid changes into liquid state 
by absorbing heat energy is called melting point.
(b) Boiling point: It is the temperature at which a liquid changes into vapour under 
atmospheric pressure.
(c) Evaporation: The slow passing of molecules of a liquid into gaseous state at a 
temperature below its boiling point.
(d) Freezing: It is a process in which a liquid changes into solid state by giving out heat 
energy.
Solution 2.
Boiling point of a liquid can be raised by increasing the atmospheric pressure.
Solution 3.
On heating, solid wax melts into liquid wax, which on further heating, is converted into 
wax vapours. These changes can be seen in a burning candle. The candle is made up of a 
solid wax. When we light a candle, the wax near its wick melts. The molten wax rises up 
the wick and is converted into wax vapour. The wax vapour mixes with oxygen in the air 
and burns. In a lighted candle, you can see the solid and the liquid states of wax. The 
vapour of wax can be seen rising from the wick for some time after the candle is put out. 
Solution 4.
(a) Sublimation: The process by which a solid directly change to its vapour state (or 
gaseous state) without passing through liquid state and vice versa is called sublimation.
(b) Liquefaction: It is a process of change of state of a substance from gaseous state to 
liquid state at a particular temperature. It is also known as condensation.
(c) Melting: It is process of changing from solid state to a liquid state at a particular 
temperature.
(d) Boiling: The process by which a liquid rapidly changes into a gaseous state, by 
absorbing the heat energy is called boiling.
Solution 5.
(a)
An atom A molecule
Atom is a smallest particle of an 
element.
Molecule is a group of two or more 
atoms combined together so it is 
bigger.
Atom consists of nucleus 
(containing protons and neutrons) 
and electrons.
Molecule consists of combination 
of two or more like or different 
atoms chemically bound together 
e.g. H
2
, HCl, NaCl etc.
Atom can neither be seen through 
naked eye nor through magnifying 
microscope.
Molecule is not visible to naked 
eye, while can be seen through 
highly magnifying microscope.
Atom cannot be further divided.
Molecule can further be divided to 
give individual atoms.
Atoms may or may not have 
independent existence.
Molecules are capable of having 
independent existence. For 
example, atom of oxygen (O) has 
no independent existence while its 
molecule exists as O
2
in nature.
(b)
Boiling Evaporation
Boiling is the process in which 
liquid gets converted into gaseous 
state.
Evaporation is a process in which 
the liquid gets converted into its 
gaseous form at any temperature 
below its boiling point.
Boiling occurs at the entire mass 
of the liquid. That is, it is a bulk 
phenomenon.
Evaporation occurs on the surface 
of the liquid. That is, it is a 
surface phenomenon.
Boiling occurs rapidly. Evaporation is a slow process.
Page 3


Chapter 1. Matter and its Composition
Exercise 1
Solution 1.
(a) Melting point: The constant temperature at which a solid changes into liquid state 
by absorbing heat energy is called melting point.
(b) Boiling point: It is the temperature at which a liquid changes into vapour under 
atmospheric pressure.
(c) Evaporation: The slow passing of molecules of a liquid into gaseous state at a 
temperature below its boiling point.
(d) Freezing: It is a process in which a liquid changes into solid state by giving out heat 
energy.
Solution 2.
Boiling point of a liquid can be raised by increasing the atmospheric pressure.
Solution 3.
On heating, solid wax melts into liquid wax, which on further heating, is converted into 
wax vapours. These changes can be seen in a burning candle. The candle is made up of a 
solid wax. When we light a candle, the wax near its wick melts. The molten wax rises up 
the wick and is converted into wax vapour. The wax vapour mixes with oxygen in the air 
and burns. In a lighted candle, you can see the solid and the liquid states of wax. The 
vapour of wax can be seen rising from the wick for some time after the candle is put out. 
Solution 4.
(a) Sublimation: The process by which a solid directly change to its vapour state (or 
gaseous state) without passing through liquid state and vice versa is called sublimation.
(b) Liquefaction: It is a process of change of state of a substance from gaseous state to 
liquid state at a particular temperature. It is also known as condensation.
(c) Melting: It is process of changing from solid state to a liquid state at a particular 
temperature.
(d) Boiling: The process by which a liquid rapidly changes into a gaseous state, by 
absorbing the heat energy is called boiling.
Solution 5.
(a)
An atom A molecule
Atom is a smallest particle of an 
element.
Molecule is a group of two or more 
atoms combined together so it is 
bigger.
Atom consists of nucleus 
(containing protons and neutrons) 
and electrons.
Molecule consists of combination 
of two or more like or different 
atoms chemically bound together 
e.g. H
2
, HCl, NaCl etc.
Atom can neither be seen through 
naked eye nor through magnifying 
microscope.
Molecule is not visible to naked 
eye, while can be seen through 
highly magnifying microscope.
Atom cannot be further divided.
Molecule can further be divided to 
give individual atoms.
Atoms may or may not have 
independent existence.
Molecules are capable of having 
independent existence. For 
example, atom of oxygen (O) has 
no independent existence while its 
molecule exists as O
2
in nature.
(b)
Boiling Evaporation
Boiling is the process in which 
liquid gets converted into gaseous 
state.
Evaporation is a process in which 
the liquid gets converted into its 
gaseous form at any temperature 
below its boiling point.
Boiling occurs at the entire mass 
of the liquid. That is, it is a bulk 
phenomenon.
Evaporation occurs on the surface 
of the liquid. That is, it is a 
surface phenomenon.
Boiling occurs rapidly. Evaporation is a slow process.
Boiling occurs at a specific 
temperature.
Evaporation occurs at any 
temperature.
(c)
Melting Boiling
The process of changing from 
solid state to a liquid state at a 
particulartemperature is called 
melting or fusion.
The process of change of liquid 
to vapour form all parts of 
the liquid at a particular 
temperature is called boiling.
Melting refers to the phenomenon 
when a solid transforms into a 
liquid.
Boiling refers to the phenomenon 
when liquid transform into a gas.
Example: Melting of ice Example: Boiling of water
(d)
Gas Vapour
A substance exists as a gas at the 
room temperature and 
atmospheric pressure.
A substance is a solid or liquid 
under ordinary condition but it 
is gaseousunder specific 
conditions.
It is present at ordinary conditions 
of temperature.
Its temperature is lower than the 
boiling point of its liquid state.
e.g. – Nitrogen, oxygen. e.g. – Iodine, Camphor
Solution 6.
(a) Water boils of 100
o
C under 1 atmosphere pressure. 
(b) At high altitude water boils below 100
o
C. 
(c) A liquid evaporates below its boiling point. 
(d) When a substance is heated kinetic energy of the particles increases. 
(e) Solids have the negligible inter-particle space. 
(f) Gases have the negligible inter-particle forces.
Solution 7.
(a) Increase in atmospheric pressure 
(b) Sulphur 
(c) Inter-conversion of state of matter
Solution 8.
(a) Sublimation 
(b) Melting 
Page 4


Chapter 1. Matter and its Composition
Exercise 1
Solution 1.
(a) Melting point: The constant temperature at which a solid changes into liquid state 
by absorbing heat energy is called melting point.
(b) Boiling point: It is the temperature at which a liquid changes into vapour under 
atmospheric pressure.
(c) Evaporation: The slow passing of molecules of a liquid into gaseous state at a 
temperature below its boiling point.
(d) Freezing: It is a process in which a liquid changes into solid state by giving out heat 
energy.
Solution 2.
Boiling point of a liquid can be raised by increasing the atmospheric pressure.
Solution 3.
On heating, solid wax melts into liquid wax, which on further heating, is converted into 
wax vapours. These changes can be seen in a burning candle. The candle is made up of a 
solid wax. When we light a candle, the wax near its wick melts. The molten wax rises up 
the wick and is converted into wax vapour. The wax vapour mixes with oxygen in the air 
and burns. In a lighted candle, you can see the solid and the liquid states of wax. The 
vapour of wax can be seen rising from the wick for some time after the candle is put out. 
Solution 4.
(a) Sublimation: The process by which a solid directly change to its vapour state (or 
gaseous state) without passing through liquid state and vice versa is called sublimation.
(b) Liquefaction: It is a process of change of state of a substance from gaseous state to 
liquid state at a particular temperature. It is also known as condensation.
(c) Melting: It is process of changing from solid state to a liquid state at a particular 
temperature.
(d) Boiling: The process by which a liquid rapidly changes into a gaseous state, by 
absorbing the heat energy is called boiling.
Solution 5.
(a)
An atom A molecule
Atom is a smallest particle of an 
element.
Molecule is a group of two or more 
atoms combined together so it is 
bigger.
Atom consists of nucleus 
(containing protons and neutrons) 
and electrons.
Molecule consists of combination 
of two or more like or different 
atoms chemically bound together 
e.g. H
2
, HCl, NaCl etc.
Atom can neither be seen through 
naked eye nor through magnifying 
microscope.
Molecule is not visible to naked 
eye, while can be seen through 
highly magnifying microscope.
Atom cannot be further divided.
Molecule can further be divided to 
give individual atoms.
Atoms may or may not have 
independent existence.
Molecules are capable of having 
independent existence. For 
example, atom of oxygen (O) has 
no independent existence while its 
molecule exists as O
2
in nature.
(b)
Boiling Evaporation
Boiling is the process in which 
liquid gets converted into gaseous 
state.
Evaporation is a process in which 
the liquid gets converted into its 
gaseous form at any temperature 
below its boiling point.
Boiling occurs at the entire mass 
of the liquid. That is, it is a bulk 
phenomenon.
Evaporation occurs on the surface 
of the liquid. That is, it is a 
surface phenomenon.
Boiling occurs rapidly. Evaporation is a slow process.
Boiling occurs at a specific 
temperature.
Evaporation occurs at any 
temperature.
(c)
Melting Boiling
The process of changing from 
solid state to a liquid state at a 
particulartemperature is called 
melting or fusion.
The process of change of liquid 
to vapour form all parts of 
the liquid at a particular 
temperature is called boiling.
Melting refers to the phenomenon 
when a solid transforms into a 
liquid.
Boiling refers to the phenomenon 
when liquid transform into a gas.
Example: Melting of ice Example: Boiling of water
(d)
Gas Vapour
A substance exists as a gas at the 
room temperature and 
atmospheric pressure.
A substance is a solid or liquid 
under ordinary condition but it 
is gaseousunder specific 
conditions.
It is present at ordinary conditions 
of temperature.
Its temperature is lower than the 
boiling point of its liquid state.
e.g. – Nitrogen, oxygen. e.g. – Iodine, Camphor
Solution 6.
(a) Water boils of 100
o
C under 1 atmosphere pressure. 
(b) At high altitude water boils below 100
o
C. 
(c) A liquid evaporates below its boiling point. 
(d) When a substance is heated kinetic energy of the particles increases. 
(e) Solids have the negligible inter-particle space. 
(f) Gases have the negligible inter-particle forces.
Solution 7.
(a) Increase in atmospheric pressure 
(b) Sulphur 
(c) Inter-conversion of state of matter
Solution 8.
(a) Sublimation 
(b) Melting 
(c) Evaporation 
(d) Vaporisation
Solution 9.
(a) Increase in temperature favours Evaporation. When evaporation occurs, remaining 
liquid becomes cooler. The particles of the liquid absorb heat energy from surroundings to 
regain energy lost during evaporation which makes the surroundings cold.
(b) Earthen pot has pores which help in evaporation. Some of the water continuously 
seeps out from these pores. This water absorbs heat of vaporization from the remaining 
water and gets evaporate. Thus, the remaining water loses heat and gets cooled.
(c) This happens because, when the petrol changes from liquid state to the vapour state, 
is absorbs heat energy from the palm. The palm thus loses heat and gets cooled.
(d) In humid weather wet clothes take longer time to dry up due to the slow evaporation 
of water from their surface.
(e) Evaporation is a surface phenomenon. With increase in surface area, evaporation 
increases. Hot tea in Saucer cools faster than in a cup and hence we can sip faster.
Solution 10.
(a) Naphthalene balls become smaller day by day as they have very weak force of 
attraction operating between their particles, which break away from other particles from 
the surface of solid without heating.
(b) In gases the particles are far apart and there is enough space available for 
compression. Hence, gases can be compressed easily.
(c) Heat energy supplied increases the rate of vibration of the particles and decreases. 
The inter-particle attraction.
(d) Light has no mass and it does it occupy space. Thus, it is not considered as matter.
(e) According to ‘Law of Conservation of Mass’, “Mass can neither be created nor 
destroyed in a chemical reaction.” However, it may change from one form to other.
Solution 11.
In summers, we perspire more. Cotton being a good absorber of water helps in absorbing 
the sweat and exposes it to the atmosphere for evaporation. When sweat evaporates 
from our body, it takes heat from our body. The heat energy equal to the latent heat of 
vaporisation is absorbed from the body leaving the body cool.
Solution 12.
Balloon get heat from sun and on heating, the vibration of particles increases and the 
inter-particle force of attraction between them gets reduced, therefore, balloon bursts.
Solution 13.
Page 5


Chapter 1. Matter and its Composition
Exercise 1
Solution 1.
(a) Melting point: The constant temperature at which a solid changes into liquid state 
by absorbing heat energy is called melting point.
(b) Boiling point: It is the temperature at which a liquid changes into vapour under 
atmospheric pressure.
(c) Evaporation: The slow passing of molecules of a liquid into gaseous state at a 
temperature below its boiling point.
(d) Freezing: It is a process in which a liquid changes into solid state by giving out heat 
energy.
Solution 2.
Boiling point of a liquid can be raised by increasing the atmospheric pressure.
Solution 3.
On heating, solid wax melts into liquid wax, which on further heating, is converted into 
wax vapours. These changes can be seen in a burning candle. The candle is made up of a 
solid wax. When we light a candle, the wax near its wick melts. The molten wax rises up 
the wick and is converted into wax vapour. The wax vapour mixes with oxygen in the air 
and burns. In a lighted candle, you can see the solid and the liquid states of wax. The 
vapour of wax can be seen rising from the wick for some time after the candle is put out. 
Solution 4.
(a) Sublimation: The process by which a solid directly change to its vapour state (or 
gaseous state) without passing through liquid state and vice versa is called sublimation.
(b) Liquefaction: It is a process of change of state of a substance from gaseous state to 
liquid state at a particular temperature. It is also known as condensation.
(c) Melting: It is process of changing from solid state to a liquid state at a particular 
temperature.
(d) Boiling: The process by which a liquid rapidly changes into a gaseous state, by 
absorbing the heat energy is called boiling.
Solution 5.
(a)
An atom A molecule
Atom is a smallest particle of an 
element.
Molecule is a group of two or more 
atoms combined together so it is 
bigger.
Atom consists of nucleus 
(containing protons and neutrons) 
and electrons.
Molecule consists of combination 
of two or more like or different 
atoms chemically bound together 
e.g. H
2
, HCl, NaCl etc.
Atom can neither be seen through 
naked eye nor through magnifying 
microscope.
Molecule is not visible to naked 
eye, while can be seen through 
highly magnifying microscope.
Atom cannot be further divided.
Molecule can further be divided to 
give individual atoms.
Atoms may or may not have 
independent existence.
Molecules are capable of having 
independent existence. For 
example, atom of oxygen (O) has 
no independent existence while its 
molecule exists as O
2
in nature.
(b)
Boiling Evaporation
Boiling is the process in which 
liquid gets converted into gaseous 
state.
Evaporation is a process in which 
the liquid gets converted into its 
gaseous form at any temperature 
below its boiling point.
Boiling occurs at the entire mass 
of the liquid. That is, it is a bulk 
phenomenon.
Evaporation occurs on the surface 
of the liquid. That is, it is a 
surface phenomenon.
Boiling occurs rapidly. Evaporation is a slow process.
Boiling occurs at a specific 
temperature.
Evaporation occurs at any 
temperature.
(c)
Melting Boiling
The process of changing from 
solid state to a liquid state at a 
particulartemperature is called 
melting or fusion.
The process of change of liquid 
to vapour form all parts of 
the liquid at a particular 
temperature is called boiling.
Melting refers to the phenomenon 
when a solid transforms into a 
liquid.
Boiling refers to the phenomenon 
when liquid transform into a gas.
Example: Melting of ice Example: Boiling of water
(d)
Gas Vapour
A substance exists as a gas at the 
room temperature and 
atmospheric pressure.
A substance is a solid or liquid 
under ordinary condition but it 
is gaseousunder specific 
conditions.
It is present at ordinary conditions 
of temperature.
Its temperature is lower than the 
boiling point of its liquid state.
e.g. – Nitrogen, oxygen. e.g. – Iodine, Camphor
Solution 6.
(a) Water boils of 100
o
C under 1 atmosphere pressure. 
(b) At high altitude water boils below 100
o
C. 
(c) A liquid evaporates below its boiling point. 
(d) When a substance is heated kinetic energy of the particles increases. 
(e) Solids have the negligible inter-particle space. 
(f) Gases have the negligible inter-particle forces.
Solution 7.
(a) Increase in atmospheric pressure 
(b) Sulphur 
(c) Inter-conversion of state of matter
Solution 8.
(a) Sublimation 
(b) Melting 
(c) Evaporation 
(d) Vaporisation
Solution 9.
(a) Increase in temperature favours Evaporation. When evaporation occurs, remaining 
liquid becomes cooler. The particles of the liquid absorb heat energy from surroundings to 
regain energy lost during evaporation which makes the surroundings cold.
(b) Earthen pot has pores which help in evaporation. Some of the water continuously 
seeps out from these pores. This water absorbs heat of vaporization from the remaining 
water and gets evaporate. Thus, the remaining water loses heat and gets cooled.
(c) This happens because, when the petrol changes from liquid state to the vapour state, 
is absorbs heat energy from the palm. The palm thus loses heat and gets cooled.
(d) In humid weather wet clothes take longer time to dry up due to the slow evaporation 
of water from their surface.
(e) Evaporation is a surface phenomenon. With increase in surface area, evaporation 
increases. Hot tea in Saucer cools faster than in a cup and hence we can sip faster.
Solution 10.
(a) Naphthalene balls become smaller day by day as they have very weak force of 
attraction operating between their particles, which break away from other particles from 
the surface of solid without heating.
(b) In gases the particles are far apart and there is enough space available for 
compression. Hence, gases can be compressed easily.
(c) Heat energy supplied increases the rate of vibration of the particles and decreases. 
The inter-particle attraction.
(d) Light has no mass and it does it occupy space. Thus, it is not considered as matter.
(e) According to ‘Law of Conservation of Mass’, “Mass can neither be created nor 
destroyed in a chemical reaction.” However, it may change from one form to other.
Solution 11.
In summers, we perspire more. Cotton being a good absorber of water helps in absorbing 
the sweat and exposes it to the atmosphere for evaporation. When sweat evaporates 
from our body, it takes heat from our body. The heat energy equal to the latent heat of 
vaporisation is absorbed from the body leaving the body cool.
Solution 12.
Balloon get heat from sun and on heating, the vibration of particles increases and the 
inter-particle force of attraction between them gets reduced, therefore, balloon bursts.
Solution 13.
Law of conservation of mass: It states that mass can neither be created nor destroyed 
in a chemical reaction. During any change, physical or chemical, matter is neither 
created nor destroyed. However it may change from one form to another.
Experimental Verification of Law of Conservation of Mass
Requirements: H-shaped tube called Landolt’s tube, Sodium chloride solution, silver 
nitrate solution, etc.
Procedure: A specially designed H-shaped tube is taken. Sodium chloride solution is 
taken in one limb ofthe tube and silver nitrate solution in the other limb as shown in 
figure. Both the limbs are now sealed and weighed. Now the tubes is averted so that the 
solutionscan mix up together and react chemically. The reaction takes place and a white 
precipitate of silver chloride is obtained.
 
The tube is weighed again. The mass of the tube is found to be exactly the same as the 
mass obtained before inverting the tube. Thus, this experiment clearly verifies the law of 
conservation of mass 
Solution 14.