Selina Textbook Solutions: Matter | Physics Class 6 ICSE PDF Download

 Page 1


Synposis 
?  Matter is the substance which occupies space and has mass. 
?  The three states of matter are 
1.  solid, 
2.  liquid 
3.  gas. 
?  Matter is composed of large number of molecules. 
?  A molecule is the smallest particle which can exist freely in nature by itself and it 
retains the properties of the substance. 
?  All molecules of a substance are identical, but the molecules of different 
substanes are different. 
?  A molecule is very small in size (10
-10
 m). 
?  The molecules are separated from each other with spaces called inter-molecular 
spacing. 
?  The molecules in a substance are held together by the forces acting between the 
molecules which are called the inter-molecular forces. 
?  The force of attraction between the molecules of the same sub¬stance is called 
the force of cohesion, while the force of attraction between the molecules of two 
different substances is called the force of adhesion. 
?  The forces of cohesion and adhesion are effective only when the separation 
between the molecules is 10
-9
 m. When the separation becomes more, they 
vanish. 
?  The molecules in a substance are not at rest, but they are con¬stantly in motion. 
?  In a solid, the molecules are rigid, the inter-molecular spacing is least, the inter-
molecular forces are strongest and the molecules remain in their fixed positions. 
They vibrate to and fro about their mean positions, but they do not leave their 
positions, so a solid has a definite shape and a definite volume. 
?  In a liquid, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids, the inter-molecular forces are weak and the molecules are free to 
move within the boundary of the liquid, so the liquid has a definite volume, but it 
does not have a definite shape. 
?  In gases, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids and liquids, the inter-molecular forces are weakest and the 
molecules are free to move anywhere in space. So the gas has neither a definite 
volume nor a definite shape. 
Activity – 2 
Classify 20 objects around you as solids, liquids and gases 
Solids : Ice, Aluminium, Silver, Calcium, Gold, Iron, Sodium, chloride, Sugar, Wood. 
Page 2


Synposis 
?  Matter is the substance which occupies space and has mass. 
?  The three states of matter are 
1.  solid, 
2.  liquid 
3.  gas. 
?  Matter is composed of large number of molecules. 
?  A molecule is the smallest particle which can exist freely in nature by itself and it 
retains the properties of the substance. 
?  All molecules of a substance are identical, but the molecules of different 
substanes are different. 
?  A molecule is very small in size (10
-10
 m). 
?  The molecules are separated from each other with spaces called inter-molecular 
spacing. 
?  The molecules in a substance are held together by the forces acting between the 
molecules which are called the inter-molecular forces. 
?  The force of attraction between the molecules of the same sub¬stance is called 
the force of cohesion, while the force of attraction between the molecules of two 
different substances is called the force of adhesion. 
?  The forces of cohesion and adhesion are effective only when the separation 
between the molecules is 10
-9
 m. When the separation becomes more, they 
vanish. 
?  The molecules in a substance are not at rest, but they are con¬stantly in motion. 
?  In a solid, the molecules are rigid, the inter-molecular spacing is least, the inter-
molecular forces are strongest and the molecules remain in their fixed positions. 
They vibrate to and fro about their mean positions, but they do not leave their 
positions, so a solid has a definite shape and a definite volume. 
?  In a liquid, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids, the inter-molecular forces are weak and the molecules are free to 
move within the boundary of the liquid, so the liquid has a definite volume, but it 
does not have a definite shape. 
?  In gases, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids and liquids, the inter-molecular forces are weakest and the 
molecules are free to move anywhere in space. So the gas has neither a definite 
volume nor a definite shape. 
Activity – 2 
Classify 20 objects around you as solids, liquids and gases 
Solids : Ice, Aluminium, Silver, Calcium, Gold, Iron, Sodium, chloride, Sugar, Wood. 
Liquids : Water, benzene, chloroform, oil, honey, glycerine, hydrochloric acid, alcohol, 
dettol. 
Gases : Steam, Air, Oxygen, Hydrogen, Chlorine, Nitrogen, Ammonia, Helium, Argon. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The molecules of each substance are identical. 
Answer. False 
(b) The inter-molecular forces are effective at all distances between the two molecules. 
Answer. False 
(c) The molecules in a substance arc in random motion. 
Answer. Tme 
(d) In a gas, the molecules can move anywhere in space. . 
Answer. Tme 
(e) The liquids are less viscous than the gases. 
Answer. False 
2. Fill in the blanks 
(a) All the molecules of a substance are identical. 
(b) The inter-molecular spacing is least in solids more in liquids and still more in 
gases. 
(c) The molecular motion in liquid and gas is in zig-zag path. 
(d) In a solid, the molecules vibrate to and fro but they remain at their fixed positions. 
(e) The inter-molecular forces are the weakest in gases. 
(f) A solid exerts pressure downwards on its base. 
(g) The gases are least dense. 
(h) A solid is most rigid. 
3. Select the correct alternative 
(a) The diameter of a molecule is approximately 
Page 3


Synposis 
?  Matter is the substance which occupies space and has mass. 
?  The three states of matter are 
1.  solid, 
2.  liquid 
3.  gas. 
?  Matter is composed of large number of molecules. 
?  A molecule is the smallest particle which can exist freely in nature by itself and it 
retains the properties of the substance. 
?  All molecules of a substance are identical, but the molecules of different 
substanes are different. 
?  A molecule is very small in size (10
-10
 m). 
?  The molecules are separated from each other with spaces called inter-molecular 
spacing. 
?  The molecules in a substance are held together by the forces acting between the 
molecules which are called the inter-molecular forces. 
?  The force of attraction between the molecules of the same sub¬stance is called 
the force of cohesion, while the force of attraction between the molecules of two 
different substances is called the force of adhesion. 
?  The forces of cohesion and adhesion are effective only when the separation 
between the molecules is 10
-9
 m. When the separation becomes more, they 
vanish. 
?  The molecules in a substance are not at rest, but they are con¬stantly in motion. 
?  In a solid, the molecules are rigid, the inter-molecular spacing is least, the inter-
molecular forces are strongest and the molecules remain in their fixed positions. 
They vibrate to and fro about their mean positions, but they do not leave their 
positions, so a solid has a definite shape and a definite volume. 
?  In a liquid, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids, the inter-molecular forces are weak and the molecules are free to 
move within the boundary of the liquid, so the liquid has a definite volume, but it 
does not have a definite shape. 
?  In gases, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids and liquids, the inter-molecular forces are weakest and the 
molecules are free to move anywhere in space. So the gas has neither a definite 
volume nor a definite shape. 
Activity – 2 
Classify 20 objects around you as solids, liquids and gases 
Solids : Ice, Aluminium, Silver, Calcium, Gold, Iron, Sodium, chloride, Sugar, Wood. 
Liquids : Water, benzene, chloroform, oil, honey, glycerine, hydrochloric acid, alcohol, 
dettol. 
Gases : Steam, Air, Oxygen, Hydrogen, Chlorine, Nitrogen, Ammonia, Helium, Argon. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The molecules of each substance are identical. 
Answer. False 
(b) The inter-molecular forces are effective at all distances between the two molecules. 
Answer. False 
(c) The molecules in a substance arc in random motion. 
Answer. Tme 
(d) In a gas, the molecules can move anywhere in space. . 
Answer. Tme 
(e) The liquids are less viscous than the gases. 
Answer. False 
2. Fill in the blanks 
(a) All the molecules of a substance are identical. 
(b) The inter-molecular spacing is least in solids more in liquids and still more in 
gases. 
(c) The molecular motion in liquid and gas is in zig-zag path. 
(d) In a solid, the molecules vibrate to and fro but they remain at their fixed positions. 
(e) The inter-molecular forces are the weakest in gases. 
(f) A solid exerts pressure downwards on its base. 
(g) The gases are least dense. 
(h) A solid is most rigid. 
3. Select the correct alternative 
(a) The diameter of a molecule is approximately 
1.  1 cm 
2.  10 cm 
3.  10
-10
 m 
4.  1 m 
(b) The inter-molecular forces are strongest in 
1.  solids 
2.  liquids 
3.  gases 
4.  both (i) and (ii) 
(c) The molecules 
1.  in solid, liquid and gas, move freely anywhere. 
2.  in a solid, move freely within its boundary. 
3.  in a liquid, move within its boundary. 
4.  in a gas, move only within its boundary. 
(d) The solids are 
1.  more dense 
2.  less dense 
3.  least dense 
4.  highly compressible 
(e) The inter-molecular forces in liquids are 
1.  as strong as in solids 
2.  stronger than in solids 
3.  weaker than in solids 
4.  weaker than in gases 
Page 4


Synposis 
?  Matter is the substance which occupies space and has mass. 
?  The three states of matter are 
1.  solid, 
2.  liquid 
3.  gas. 
?  Matter is composed of large number of molecules. 
?  A molecule is the smallest particle which can exist freely in nature by itself and it 
retains the properties of the substance. 
?  All molecules of a substance are identical, but the molecules of different 
substanes are different. 
?  A molecule is very small in size (10
-10
 m). 
?  The molecules are separated from each other with spaces called inter-molecular 
spacing. 
?  The molecules in a substance are held together by the forces acting between the 
molecules which are called the inter-molecular forces. 
?  The force of attraction between the molecules of the same sub¬stance is called 
the force of cohesion, while the force of attraction between the molecules of two 
different substances is called the force of adhesion. 
?  The forces of cohesion and adhesion are effective only when the separation 
between the molecules is 10
-9
 m. When the separation becomes more, they 
vanish. 
?  The molecules in a substance are not at rest, but they are con¬stantly in motion. 
?  In a solid, the molecules are rigid, the inter-molecular spacing is least, the inter-
molecular forces are strongest and the molecules remain in their fixed positions. 
They vibrate to and fro about their mean positions, but they do not leave their 
positions, so a solid has a definite shape and a definite volume. 
?  In a liquid, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids, the inter-molecular forces are weak and the molecules are free to 
move within the boundary of the liquid, so the liquid has a definite volume, but it 
does not have a definite shape. 
?  In gases, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids and liquids, the inter-molecular forces are weakest and the 
molecules are free to move anywhere in space. So the gas has neither a definite 
volume nor a definite shape. 
Activity – 2 
Classify 20 objects around you as solids, liquids and gases 
Solids : Ice, Aluminium, Silver, Calcium, Gold, Iron, Sodium, chloride, Sugar, Wood. 
Liquids : Water, benzene, chloroform, oil, honey, glycerine, hydrochloric acid, alcohol, 
dettol. 
Gases : Steam, Air, Oxygen, Hydrogen, Chlorine, Nitrogen, Ammonia, Helium, Argon. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The molecules of each substance are identical. 
Answer. False 
(b) The inter-molecular forces are effective at all distances between the two molecules. 
Answer. False 
(c) The molecules in a substance arc in random motion. 
Answer. Tme 
(d) In a gas, the molecules can move anywhere in space. . 
Answer. Tme 
(e) The liquids are less viscous than the gases. 
Answer. False 
2. Fill in the blanks 
(a) All the molecules of a substance are identical. 
(b) The inter-molecular spacing is least in solids more in liquids and still more in 
gases. 
(c) The molecular motion in liquid and gas is in zig-zag path. 
(d) In a solid, the molecules vibrate to and fro but they remain at their fixed positions. 
(e) The inter-molecular forces are the weakest in gases. 
(f) A solid exerts pressure downwards on its base. 
(g) The gases are least dense. 
(h) A solid is most rigid. 
3. Select the correct alternative 
(a) The diameter of a molecule is approximately 
1.  1 cm 
2.  10 cm 
3.  10
-10
 m 
4.  1 m 
(b) The inter-molecular forces are strongest in 
1.  solids 
2.  liquids 
3.  gases 
4.  both (i) and (ii) 
(c) The molecules 
1.  in solid, liquid and gas, move freely anywhere. 
2.  in a solid, move freely within its boundary. 
3.  in a liquid, move within its boundary. 
4.  in a gas, move only within its boundary. 
(d) The solids are 
1.  more dense 
2.  less dense 
3.  least dense 
4.  highly compressible 
(e) The inter-molecular forces in liquids are 
1.  as strong as in solids 
2.  stronger than in solids 
3.  weaker than in solids 
4.  weaker than in gases 
5. 4. Match the following columns 
 
 
B. Short/Long answer questions 
Question 1. 
Define matter. What is its composition ? 
Answer: 
Matter is defined as anything which occupies space and has mass. It can be perceived 
by our sense of smell, touch, sight, hearing and taste. 
Matter is composed of tiny particles known as atoms. 
Question 2. 
Name the three states of matter. 
Answer: 
The three states of matter are solids, liquids and gases. 
Solids —A solid has a definite shape and definite volume. 
Example – wood, stone, iron, ice etc. 
Liquid —A liquid has a definite volume but not definite shape. 
Example — water, juice, milk, oil, etc. 
Gases —A gas neither has definite shape nor a definite volume. 
Example – air, hydrogen, oxygen, watervapour etc. 
Page 5


Synposis 
?  Matter is the substance which occupies space and has mass. 
?  The three states of matter are 
1.  solid, 
2.  liquid 
3.  gas. 
?  Matter is composed of large number of molecules. 
?  A molecule is the smallest particle which can exist freely in nature by itself and it 
retains the properties of the substance. 
?  All molecules of a substance are identical, but the molecules of different 
substanes are different. 
?  A molecule is very small in size (10
-10
 m). 
?  The molecules are separated from each other with spaces called inter-molecular 
spacing. 
?  The molecules in a substance are held together by the forces acting between the 
molecules which are called the inter-molecular forces. 
?  The force of attraction between the molecules of the same sub¬stance is called 
the force of cohesion, while the force of attraction between the molecules of two 
different substances is called the force of adhesion. 
?  The forces of cohesion and adhesion are effective only when the separation 
between the molecules is 10
-9
 m. When the separation becomes more, they 
vanish. 
?  The molecules in a substance are not at rest, but they are con¬stantly in motion. 
?  In a solid, the molecules are rigid, the inter-molecular spacing is least, the inter-
molecular forces are strongest and the molecules remain in their fixed positions. 
They vibrate to and fro about their mean positions, but they do not leave their 
positions, so a solid has a definite shape and a definite volume. 
?  In a liquid, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids, the inter-molecular forces are weak and the molecules are free to 
move within the boundary of the liquid, so the liquid has a definite volume, but it 
does not have a definite shape. 
?  In gases, the molecules are not rigid, the inter-molecular spacing is more than 
that in solids and liquids, the inter-molecular forces are weakest and the 
molecules are free to move anywhere in space. So the gas has neither a definite 
volume nor a definite shape. 
Activity – 2 
Classify 20 objects around you as solids, liquids and gases 
Solids : Ice, Aluminium, Silver, Calcium, Gold, Iron, Sodium, chloride, Sugar, Wood. 
Liquids : Water, benzene, chloroform, oil, honey, glycerine, hydrochloric acid, alcohol, 
dettol. 
Gases : Steam, Air, Oxygen, Hydrogen, Chlorine, Nitrogen, Ammonia, Helium, Argon. 
Test yourself 
A. Objective Questions 
1. Write true or false for each statement 
(a) The molecules of each substance are identical. 
Answer. False 
(b) The inter-molecular forces are effective at all distances between the two molecules. 
Answer. False 
(c) The molecules in a substance arc in random motion. 
Answer. Tme 
(d) In a gas, the molecules can move anywhere in space. . 
Answer. Tme 
(e) The liquids are less viscous than the gases. 
Answer. False 
2. Fill in the blanks 
(a) All the molecules of a substance are identical. 
(b) The inter-molecular spacing is least in solids more in liquids and still more in 
gases. 
(c) The molecular motion in liquid and gas is in zig-zag path. 
(d) In a solid, the molecules vibrate to and fro but they remain at their fixed positions. 
(e) The inter-molecular forces are the weakest in gases. 
(f) A solid exerts pressure downwards on its base. 
(g) The gases are least dense. 
(h) A solid is most rigid. 
3. Select the correct alternative 
(a) The diameter of a molecule is approximately 
1.  1 cm 
2.  10 cm 
3.  10
-10
 m 
4.  1 m 
(b) The inter-molecular forces are strongest in 
1.  solids 
2.  liquids 
3.  gases 
4.  both (i) and (ii) 
(c) The molecules 
1.  in solid, liquid and gas, move freely anywhere. 
2.  in a solid, move freely within its boundary. 
3.  in a liquid, move within its boundary. 
4.  in a gas, move only within its boundary. 
(d) The solids are 
1.  more dense 
2.  less dense 
3.  least dense 
4.  highly compressible 
(e) The inter-molecular forces in liquids are 
1.  as strong as in solids 
2.  stronger than in solids 
3.  weaker than in solids 
4.  weaker than in gases 
5. 4. Match the following columns 
 
 
B. Short/Long answer questions 
Question 1. 
Define matter. What is its composition ? 
Answer: 
Matter is defined as anything which occupies space and has mass. It can be perceived 
by our sense of smell, touch, sight, hearing and taste. 
Matter is composed of tiny particles known as atoms. 
Question 2. 
Name the three states of matter. 
Answer: 
The three states of matter are solids, liquids and gases. 
Solids —A solid has a definite shape and definite volume. 
Example – wood, stone, iron, ice etc. 
Liquid —A liquid has a definite volume but not definite shape. 
Example — water, juice, milk, oil, etc. 
Gases —A gas neither has definite shape nor a definite volume. 
Example – air, hydrogen, oxygen, watervapour etc. 
Question 3. 
What is a molecule ? 
Answer: 
The smallest unit of matter which can exist independently is called molecule. 
Example: Oxygen molecule (O 2) made up of two (O) atoms. 
Question 4. 
What is the approximate size of a molecule ? 
Answer: 
Matter is made up of molecules which are very small in size (~10
-9 
m). 
Question 5. 
One litre of water has 6.02 × 10
26
 molecules. Estimate the size of a molecule. 
Answer: 
The size of a particle (or molecule of matter is very small. 1 litre of water has 6.02 
× 10
26
 molecules, so the volume of a particle of 
 
Thus the diameter of a water molecule is nearly 1.27 × 10
-9
 metre. 
Question 6. 
What do you mean by inter-molecular spacing ? 
Answer: 
Intermolecular space — The space between any two consecutive molecules of a 
substance is called intermolecular space 
Question 7. 
Describe a simple experiment to illustrate the existence of inter-molecular spacing. 
Answer: 
Take 100 ml of water in a measuring cylinder. Add 20 gram of salt in water gently and 
stir it well so as to dissolve the salt well in water. It is noticed that the level of water does 
not change. It shows that the particles of salt occupy spaces between the particles of