Selina Textbook Solutions: Matter | Physics Class 8 ICSE PDF Download

 Page 1


1. Matter 
? Matter Every substance living and non-living that we see is made up of matter and 
MATTER “is something which has mass, occupies space and can be perceived by 
our senses.” e.g. Hydrogen, milk, oxygen, pen, table, water, iron, air, oil, sugar 
etc. 
? Matter is composed of tiny particles called molecules, which are in constant 
motion, have spaces between them and have inter-molecular attraction. 
? Every molecule can exist freely in nature and has all the properties of matter. 
? A molecule is composed of ATOMS, but atom cannot exist free in nature. 
? INTER-MOLECULAR FORCE ‘The molecules of a matter exert a force of 
attraction on each other – The force of attraction is called INTER- 
? MOLECULAR FORCE This force in solid is very strong and we cannot break a 
solid easily. In liquids this force is less strong and in molecules of gas it is very 
less. – 
? FORCE OF COHESION “The inter-molecular force of attraction between the 
molecules of same substance is called FORCE OF COHESION.” i.e. between 
water and water. 
? FORCE OF ADHESION “The force of attraction between the molecules of two 
different substances is called FORCE OF ADHESION” i.e. between glue and 
paper. 
Matter is composed of tiny particles and molecules of matter have spaces 
between them can be  
 
proved by experiment. 
Take 50 c.c of water in a measuring cylinder. Add a small quantity of salt in it. Salt 
gets dissolved in water and still level remains at 50 c.c. Where has salt gone? 
The salt molecules enter into spaces of water and water molecules into spaces of salt 
molecules. This experiment show that particles of matter are very minute and cannot 
be seen by naked eye and there are spaces between molecules. 
Page 2


1. Matter 
? Matter Every substance living and non-living that we see is made up of matter and 
MATTER “is something which has mass, occupies space and can be perceived by 
our senses.” e.g. Hydrogen, milk, oxygen, pen, table, water, iron, air, oil, sugar 
etc. 
? Matter is composed of tiny particles called molecules, which are in constant 
motion, have spaces between them and have inter-molecular attraction. 
? Every molecule can exist freely in nature and has all the properties of matter. 
? A molecule is composed of ATOMS, but atom cannot exist free in nature. 
? INTER-MOLECULAR FORCE ‘The molecules of a matter exert a force of 
attraction on each other – The force of attraction is called INTER- 
? MOLECULAR FORCE This force in solid is very strong and we cannot break a 
solid easily. In liquids this force is less strong and in molecules of gas it is very 
less. – 
? FORCE OF COHESION “The inter-molecular force of attraction between the 
molecules of same substance is called FORCE OF COHESION.” i.e. between 
water and water. 
? FORCE OF ADHESION “The force of attraction between the molecules of two 
different substances is called FORCE OF ADHESION” i.e. between glue and 
paper. 
Matter is composed of tiny particles and molecules of matter have spaces 
between them can be  
 
proved by experiment. 
Take 50 c.c of water in a measuring cylinder. Add a small quantity of salt in it. Salt 
gets dissolved in water and still level remains at 50 c.c. Where has salt gone? 
The salt molecules enter into spaces of water and water molecules into spaces of salt 
molecules. This experiment show that particles of matter are very minute and cannot 
be seen by naked eye and there are spaces between molecules. 
 
? The molecules of matter are in constant motion can be seen by opening a bottle of 
perfume in a comer of room, it reaches the other parts of the room. 
? SUBLIMATION Change of solid directly into vapours on absorbing heat. 
? DEPOSITION “The change of vapours directly into solid on cooling.” 
? MELTING “Change of solid in liquid at fixed temperature on heating.” 
? FUSION or FREEZING “Change of liquid to solid state on cooling at a fixed 
temperature.” 
? FUSION or MELTING “Change of a solid to liquid state at a fixed temperature on 
absorbing heat.” 
? EVAPORATION Surface phenomenon i.e. only takes place at surface “Is change 
of liquid to vapours.” Evaporation has cooling effect. Takes place at all 
temperatures. 
? VAPORIZATION “Change of liquid to vapour state on heating at constant 
temperature.” 
It is fast process and produces hotness. 
Test Yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The temperature of a substance remains unaffected during its change of state. 
Answer: True. 
(b) Ice melts at 100°C. 
Answer: False. The ice melts at 0° by absorption of heat. 
(c) Water at 100°C has more heat than the steam at 100°C. 
Answer: False. 
(d) Evaporation of a liquid causes cooling. 
Answer: True. 
(e) Water evaporates only at 100°C. 
Answer: False. 
Page 3


1. Matter 
? Matter Every substance living and non-living that we see is made up of matter and 
MATTER “is something which has mass, occupies space and can be perceived by 
our senses.” e.g. Hydrogen, milk, oxygen, pen, table, water, iron, air, oil, sugar 
etc. 
? Matter is composed of tiny particles called molecules, which are in constant 
motion, have spaces between them and have inter-molecular attraction. 
? Every molecule can exist freely in nature and has all the properties of matter. 
? A molecule is composed of ATOMS, but atom cannot exist free in nature. 
? INTER-MOLECULAR FORCE ‘The molecules of a matter exert a force of 
attraction on each other – The force of attraction is called INTER- 
? MOLECULAR FORCE This force in solid is very strong and we cannot break a 
solid easily. In liquids this force is less strong and in molecules of gas it is very 
less. – 
? FORCE OF COHESION “The inter-molecular force of attraction between the 
molecules of same substance is called FORCE OF COHESION.” i.e. between 
water and water. 
? FORCE OF ADHESION “The force of attraction between the molecules of two 
different substances is called FORCE OF ADHESION” i.e. between glue and 
paper. 
Matter is composed of tiny particles and molecules of matter have spaces 
between them can be  
 
proved by experiment. 
Take 50 c.c of water in a measuring cylinder. Add a small quantity of salt in it. Salt 
gets dissolved in water and still level remains at 50 c.c. Where has salt gone? 
The salt molecules enter into spaces of water and water molecules into spaces of salt 
molecules. This experiment show that particles of matter are very minute and cannot 
be seen by naked eye and there are spaces between molecules. 
 
? The molecules of matter are in constant motion can be seen by opening a bottle of 
perfume in a comer of room, it reaches the other parts of the room. 
? SUBLIMATION Change of solid directly into vapours on absorbing heat. 
? DEPOSITION “The change of vapours directly into solid on cooling.” 
? MELTING “Change of solid in liquid at fixed temperature on heating.” 
? FUSION or FREEZING “Change of liquid to solid state on cooling at a fixed 
temperature.” 
? FUSION or MELTING “Change of a solid to liquid state at a fixed temperature on 
absorbing heat.” 
? EVAPORATION Surface phenomenon i.e. only takes place at surface “Is change 
of liquid to vapours.” Evaporation has cooling effect. Takes place at all 
temperatures. 
? VAPORIZATION “Change of liquid to vapour state on heating at constant 
temperature.” 
It is fast process and produces hotness. 
Test Yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The temperature of a substance remains unaffected during its change of state. 
Answer: True. 
(b) Ice melts at 100°C. 
Answer: False. The ice melts at 0° by absorption of heat. 
(c) Water at 100°C has more heat than the steam at 100°C. 
Answer: False. 
(d) Evaporation of a liquid causes cooling. 
Answer: True. 
(e) Water evaporates only at 100°C. 
Answer: False. 
(f) Boiling takes place at all temperatures. 
Answer: False. 
(g) Evaporation takes place over the entire mass of the liquid. 
Answer: False. 
(h) The process of a gas converting directly into solid is called vaporization. 
Answer: False. 
The process of a liquid converting directly into gas is called vaporization. 
(i) At high altitudes water boils above 100° C. 
Answer: False. 
(j) The melting point of ice is 0°C. 
Answer: True. 
2. Fill in the blanks 
(a) Evaporation takes place at all temperature. 
(b) Freezing process is just reverse of melting. 
(c) Sublimation is a process that involves direct conversion of a solid into its vapour on 
heating. 
(d) The temperature at which a solid converts into a liquid is called its melting point. 
(e) The smallest unit of matter that exists freely in nature is called molecule. 
(f) Molecules of a substance are always in a state of motion and so they 
possess kinetic energy. 
(g) Intermolecular space is maximum in gases less in liquids and the least in solids. 
(h) Intermolecular force of attraction is maxiumum in solids, less in liquids and the 
least in gases. 
3. Match the following 
Page 4


1. Matter 
? Matter Every substance living and non-living that we see is made up of matter and 
MATTER “is something which has mass, occupies space and can be perceived by 
our senses.” e.g. Hydrogen, milk, oxygen, pen, table, water, iron, air, oil, sugar 
etc. 
? Matter is composed of tiny particles called molecules, which are in constant 
motion, have spaces between them and have inter-molecular attraction. 
? Every molecule can exist freely in nature and has all the properties of matter. 
? A molecule is composed of ATOMS, but atom cannot exist free in nature. 
? INTER-MOLECULAR FORCE ‘The molecules of a matter exert a force of 
attraction on each other – The force of attraction is called INTER- 
? MOLECULAR FORCE This force in solid is very strong and we cannot break a 
solid easily. In liquids this force is less strong and in molecules of gas it is very 
less. – 
? FORCE OF COHESION “The inter-molecular force of attraction between the 
molecules of same substance is called FORCE OF COHESION.” i.e. between 
water and water. 
? FORCE OF ADHESION “The force of attraction between the molecules of two 
different substances is called FORCE OF ADHESION” i.e. between glue and 
paper. 
Matter is composed of tiny particles and molecules of matter have spaces 
between them can be  
 
proved by experiment. 
Take 50 c.c of water in a measuring cylinder. Add a small quantity of salt in it. Salt 
gets dissolved in water and still level remains at 50 c.c. Where has salt gone? 
The salt molecules enter into spaces of water and water molecules into spaces of salt 
molecules. This experiment show that particles of matter are very minute and cannot 
be seen by naked eye and there are spaces between molecules. 
 
? The molecules of matter are in constant motion can be seen by opening a bottle of 
perfume in a comer of room, it reaches the other parts of the room. 
? SUBLIMATION Change of solid directly into vapours on absorbing heat. 
? DEPOSITION “The change of vapours directly into solid on cooling.” 
? MELTING “Change of solid in liquid at fixed temperature on heating.” 
? FUSION or FREEZING “Change of liquid to solid state on cooling at a fixed 
temperature.” 
? FUSION or MELTING “Change of a solid to liquid state at a fixed temperature on 
absorbing heat.” 
? EVAPORATION Surface phenomenon i.e. only takes place at surface “Is change 
of liquid to vapours.” Evaporation has cooling effect. Takes place at all 
temperatures. 
? VAPORIZATION “Change of liquid to vapour state on heating at constant 
temperature.” 
It is fast process and produces hotness. 
Test Yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The temperature of a substance remains unaffected during its change of state. 
Answer: True. 
(b) Ice melts at 100°C. 
Answer: False. The ice melts at 0° by absorption of heat. 
(c) Water at 100°C has more heat than the steam at 100°C. 
Answer: False. 
(d) Evaporation of a liquid causes cooling. 
Answer: True. 
(e) Water evaporates only at 100°C. 
Answer: False. 
(f) Boiling takes place at all temperatures. 
Answer: False. 
(g) Evaporation takes place over the entire mass of the liquid. 
Answer: False. 
(h) The process of a gas converting directly into solid is called vaporization. 
Answer: False. 
The process of a liquid converting directly into gas is called vaporization. 
(i) At high altitudes water boils above 100° C. 
Answer: False. 
(j) The melting point of ice is 0°C. 
Answer: True. 
2. Fill in the blanks 
(a) Evaporation takes place at all temperature. 
(b) Freezing process is just reverse of melting. 
(c) Sublimation is a process that involves direct conversion of a solid into its vapour on 
heating. 
(d) The temperature at which a solid converts into a liquid is called its melting point. 
(e) The smallest unit of matter that exists freely in nature is called molecule. 
(f) Molecules of a substance are always in a state of motion and so they 
possess kinetic energy. 
(g) Intermolecular space is maximum in gases less in liquids and the least in solids. 
(h) Intermolecular force of attraction is maxiumum in solids, less in liquids and the 
least in gases. 
3. Match the following 
 
4. Select the correct alternative 
(a) The inter-molecular force is maximum in 
1. solids 
2. gases 
3. liquids 
4. none of the above 
(b) The inter-molecular space is maximum in 
1. liquids 
2. solids 
3. gases 
4. none of the above 
(c) The molecules can move freely anywhere in 
1. gases 
2. liquids 
3. solids 
4. none of the above 
(d) The molecules move only within the boundary of 
1.  liquids 
2. gases 
3. solids 
4. none of the above 
(e) The temperature at which a liquid gets converted into its vapour state is called its 
1. melting point 
2. boiling point 
3. dewpoint 
4. freezing point. 
(f) Rapid conversion of water into steam is an example of 
1. evaporation 
2. freezing 
3. melting 
4. vapourization. 
Page 5


1. Matter 
? Matter Every substance living and non-living that we see is made up of matter and 
MATTER “is something which has mass, occupies space and can be perceived by 
our senses.” e.g. Hydrogen, milk, oxygen, pen, table, water, iron, air, oil, sugar 
etc. 
? Matter is composed of tiny particles called molecules, which are in constant 
motion, have spaces between them and have inter-molecular attraction. 
? Every molecule can exist freely in nature and has all the properties of matter. 
? A molecule is composed of ATOMS, but atom cannot exist free in nature. 
? INTER-MOLECULAR FORCE ‘The molecules of a matter exert a force of 
attraction on each other – The force of attraction is called INTER- 
? MOLECULAR FORCE This force in solid is very strong and we cannot break a 
solid easily. In liquids this force is less strong and in molecules of gas it is very 
less. – 
? FORCE OF COHESION “The inter-molecular force of attraction between the 
molecules of same substance is called FORCE OF COHESION.” i.e. between 
water and water. 
? FORCE OF ADHESION “The force of attraction between the molecules of two 
different substances is called FORCE OF ADHESION” i.e. between glue and 
paper. 
Matter is composed of tiny particles and molecules of matter have spaces 
between them can be  
 
proved by experiment. 
Take 50 c.c of water in a measuring cylinder. Add a small quantity of salt in it. Salt 
gets dissolved in water and still level remains at 50 c.c. Where has salt gone? 
The salt molecules enter into spaces of water and water molecules into spaces of salt 
molecules. This experiment show that particles of matter are very minute and cannot 
be seen by naked eye and there are spaces between molecules. 
 
? The molecules of matter are in constant motion can be seen by opening a bottle of 
perfume in a comer of room, it reaches the other parts of the room. 
? SUBLIMATION Change of solid directly into vapours on absorbing heat. 
? DEPOSITION “The change of vapours directly into solid on cooling.” 
? MELTING “Change of solid in liquid at fixed temperature on heating.” 
? FUSION or FREEZING “Change of liquid to solid state on cooling at a fixed 
temperature.” 
? FUSION or MELTING “Change of a solid to liquid state at a fixed temperature on 
absorbing heat.” 
? EVAPORATION Surface phenomenon i.e. only takes place at surface “Is change 
of liquid to vapours.” Evaporation has cooling effect. Takes place at all 
temperatures. 
? VAPORIZATION “Change of liquid to vapour state on heating at constant 
temperature.” 
It is fast process and produces hotness. 
Test Yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The temperature of a substance remains unaffected during its change of state. 
Answer: True. 
(b) Ice melts at 100°C. 
Answer: False. The ice melts at 0° by absorption of heat. 
(c) Water at 100°C has more heat than the steam at 100°C. 
Answer: False. 
(d) Evaporation of a liquid causes cooling. 
Answer: True. 
(e) Water evaporates only at 100°C. 
Answer: False. 
(f) Boiling takes place at all temperatures. 
Answer: False. 
(g) Evaporation takes place over the entire mass of the liquid. 
Answer: False. 
(h) The process of a gas converting directly into solid is called vaporization. 
Answer: False. 
The process of a liquid converting directly into gas is called vaporization. 
(i) At high altitudes water boils above 100° C. 
Answer: False. 
(j) The melting point of ice is 0°C. 
Answer: True. 
2. Fill in the blanks 
(a) Evaporation takes place at all temperature. 
(b) Freezing process is just reverse of melting. 
(c) Sublimation is a process that involves direct conversion of a solid into its vapour on 
heating. 
(d) The temperature at which a solid converts into a liquid is called its melting point. 
(e) The smallest unit of matter that exists freely in nature is called molecule. 
(f) Molecules of a substance are always in a state of motion and so they 
possess kinetic energy. 
(g) Intermolecular space is maximum in gases less in liquids and the least in solids. 
(h) Intermolecular force of attraction is maxiumum in solids, less in liquids and the 
least in gases. 
3. Match the following 
 
4. Select the correct alternative 
(a) The inter-molecular force is maximum in 
1. solids 
2. gases 
3. liquids 
4. none of the above 
(b) The inter-molecular space is maximum in 
1. liquids 
2. solids 
3. gases 
4. none of the above 
(c) The molecules can move freely anywhere in 
1. gases 
2. liquids 
3. solids 
4. none of the above 
(d) The molecules move only within the boundary of 
1.  liquids 
2. gases 
3. solids 
4. none of the above 
(e) The temperature at which a liquid gets converted into its vapour state is called its 
1. melting point 
2. boiling point 
3. dewpoint 
4. freezing point. 
(f) Rapid conversion of water into steam is an example of 
1. evaporation 
2. freezing 
3. melting 
4. vapourization. 
(g) Evaporation takes place from the 
1. surface of liquid 
2. throughout the liquid 
3. mid-portion of the liquid 
4. bottom of liquid. 
(h) Boiling takes place from the 
1. the surface of the liquid 
2. throughout the liquid 
3. mid-portion of liquid 
4. none of the above. 
Short/Long Answer Questions 
Question 1. 
Define the term matter. What is it composed of ? 
Answer: 
Anything which occupies space and has mass is called matter. Matter is composed of 
tiny particles called MOLECULES. 
Question 2. 
State three properties of molecules of a matter. 
Answer: 
1. They are very small in size. 
2. They have spaces between them. 
3. They are in constant motion and they posses kinetic energy. 
Question 3. 
What do you mean by the inter-molecular spaces ? How do they vary in different states 
of matter ? 
Answer: 
INTER-MOLECULAR SPACES “The spacing between the molecules of matter is called 
Inter-molecular spaces.” 
The inter-molecular spaces is less in solids more in liquids and still more in gases. 
Explanation of inter-molecular space : Take water in a measuring cylinder say upto 
80 ml. mark. Add 10 gm of salt to it. The volume in cylinder should increase. On 
dissolving salt we find volume remains same i.e. upto 80 ml mark. This is because there 
are spaces in water molecules and salt molecules occupy these spaces and volume 
remains the same.