Matter ICSE Class-8th Concise Selina Physics Solutions Chapter-1. We Provide Step by Step Answer of Objective, True False , Fill in the blanks,Match the following , Short/Long Answer Type of Exercise-1 Matter. Visit official Website  CISCE  for detail information about ICSE Board Class-8.

## Matter ICSE Class-8th Concise Selina Physics Solutions

### A. Objective Questions Chapter-1 Matter ICSE Class-8th Concise Selina

1. Write true or false for each statement

(a) The temperature of a substance remains unaffected during its change of state.

(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.

(d) Evaporation of a liquid causes cooling.

(e) Water evaporates only at 100°C.

(f) Boiling takes place at all temperatures.

(g) Evaporation takes place over the entire mass of the liquid.

(h) The process of a gas converting directly into solid is called vaporization.
The process of a liquid converting directly into gas is called vaporization.

(i) At high altitudes water boils above 100° C.

(j) The melting point of ice is 0°C.

### 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) Inter molecular space is maximum in gases less in liquids and the least in solids.
(h) Inter molecular force of attraction is maximum in solids, less in liquids and the least in gases.

### 4. Select the correct alternative

(a) The inter-molecular force is maximum in

1. solids
2. gases
3. liquids
4. none of the above

solids

(b) The inter-molecular space is maximum in

1. liquids
2. solids
3. gases
4. none of the above

gases

(c) The molecules can move freely anywhere in

1. gases
2. liquids
3. solids
4. none of the above

gases

(d) The molecules move only within the boundary of

1.  liquids
2. gases
3. solids
4. none of the above

liquids

(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.

boiling point

(f) Rapid conversion of water into steam is an example of

1. evaporation
2. freezing
3. melting
4. vaporization.

vaporization

(g) Evaporation takes place from the

1. surface of liquid
2. throughout the liquid
3. mid-portion of the liquid
4. bottom of liquid.

surface 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.

throughout the liquid

#### Question 1.

Define the term matter. What is it composed of ?
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.

1. They are very small in size.
2. molecule 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 ?
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 up to 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.

#### Question 4.

What is meant by the inter-molecular forces of attraction ?
How do they vary in solids, liquids and gases ?
INTER-MOLECULAR FORCES OF ATTRACTION : “The forces of attraction between the molecules of matter is called the inter-molecular force of attraction.”
This inter molecular force is maximum in solids, less in liquids and least in gases.

#### Question 5.

Which of the following are correct ?
(a) Solids have definite shape and definite volume.
True.
Reason As the molecules here have negligible inter-molecular distance between them and have maximum inter molecular force of attraction.
(b) Liquids have definite volume but do not have definite shape.
True.
(c) Gases have definite volume but no definite shape.
False.
Correct Gases have neither definite volume nor a definite shape.
(d) Liquids have definite shape and definite volume.
False.
Correct Liquids have a definite volume but not definite shape.

#### Question 6.

Discuss the three states of matter solid, liquids and gas on the basis of molecular model.
Solids

Here the molecules are very tightly packed that there is no or very less intermolecular space and there is high intermolecular force of attraction (force of cohesion). The molecules do not move about their mean position and thus solids have a definite shape and volume.
Liquids :

Here the molecules are less tightly packed as compared to solids and also there is lesser force of intermolecular attraction. The intermolecular distance is greater than that in the solids. Thus, they do not have a definite shape but acquire the shape of the vessel in which they are contained but have a definite volume at a given temperature.
Gases :

Here the molecules are far apart from each other i.e. have the greatest intermolecular distance which result into the weakest intermolecular forces of attraction. The molecules as are not bound by any strong force, move about freely and thus gases do not have a definite shape and’hlso do not have any definite volume.

#### Question 7.

What do you mean by the change of state ? Write the flow chart showing the complete cycle of change of state.
CHANGE OF STATE: “The process of change from one state(form) to another state (form) either by absorption or rejection of heat at a constant temperature is called the CHANGE OF STATE.”
COMPLETE CYCLE OF CHANGE OF STATE : On heating a solid changes to liquid and liquid on heating changes to vapours. On cooling vapours condense to LIQUID, LIQUIDS on cooling freeze to SOLIDS. Some SOLIDS on heating change to vapours. On rejection of heat vapours solidify.

This cycle can be shown by diagram

#### Question 8.

Differentiate between melting point and boiling point, giving atleast one example of each.
MELTING POINT:
The temperature at which a solid starts changing into LIQUID without further increase in temperature is called MELTING POINT.” Or The constant temperature at which a solid changes into liquid.”
Example : Ice (solid) melts at Q?C into water (liquid) when heated.
BOILING POINT : “The temperature at which a LIQUID start changing in vapour without further rise in temperature.
Or
‘The constant temperature at which a LIQUID starts changing into GAS (vapours)
Example : Boiling point of water (liquid) is 100°C.

#### Question 9.

Describe the process of condensation and sublimation with examples.
CONDENSATION :
“The change of vapours on cooling at fixed temperature to liquid is called condensation.”
Example: When water vapours at 100°C are cooled they change into water (liquid).
SUBLIMATION : “The process of change of solid directly into vapours on heating is called sublimation.”

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