Selina Concise Class 8 Chemistry Chapter 1 Matter Solution

Selina Concise Class 8 Chemistry Solution Chapter No. 1- ‘Matter’ For ICSE Board Students.

1) Solution:

Anything’s around us ( pen, pencil , chalk , board , desk , bench , etc.) which has mass and volume are known as matter .

The particles or molecules of matter closely attached or connect with attraction force which is known as intermolecular force of attraction.

2) Solution:

Ans :  Following are the three state of matter.

a) Solid state

b) Liquid state

c) Gas state

a) Solid State:

Solid is the state in which molecules of matter are  closely fixed with each other by intermolecular force of attraction.

Example : rock , most metal , glass , wood etc.

b) Liquid state :

Liquid is the state in which molecules of matter are loosely bond with each other and connect weak force of attraction.

Example :  water , milk , ethanol , etc.

c) Gas State :

Gas is the state in which molecules of gas are very far with each other and connect with each other by very lessor weakest force of attraction.

Example : Oxygen , Nitrogen ,  Hydrogen etc.

3) Solution:

Ans : Interconversions state of Matter:

The process of matter change into one state to another one and vice versa  , without changing in its chemical constituents are called Interconversions state of Matter .  The change in temperature and change in pressure these two factor are responsible for the change of state of Matter.

4) Solution:

Ans : Main postulate of kinetic theory of matter:

  • Matter is made up of tiny particles called atom and molecules.
  • All components molecules or atom are same or identical in one matter or homogeneous matter.
  • The molecules of matter arrange in such a way that there is space or gap present between each other . This space or gap are known as intermolecular space.
  • The molecules or atoms of matter are bond or connect with each other by the force of attraction , this force of attraction known as intermolecular force of attraction.
  • When increased temperature , increase or fast  randomly movement of molecules of matter and acquire kinetic energy , when deceased the temperature , and  movement of molecules will be decreased or slowdown.

5) Solution:

Ans :.

a) when water is kept in deep freezer it will be cooled and change into ice at 0°C.

b) When water is heated it will be change into steam or gas at 100°C.

The phenomenon of change in state of water :

Water is a liquid in a normal conditions , but when its kept in a deep freezer it will change the State of solid that is in ice at 0°C . But when ice kept in normal environment or room temperature it will melt and again changeto  liquid or water.

In the same way when water is heated it will change into steam or gas at 100°C . But when steam or gas get cooled environment it will change back to their original position that is water or liquid state. But  all these processes ( water to ice and water gas vice versa ) happened without any change of chemical properties or chemical constituents of water.

(6) Solution:

Ans :  law of conservation of mass:

Lavoisier first derived the law of conservation of mass it state the in a chemical reaction mass of reactant is equal to the mass of products . That means in a chemical reaction mass of matter is same even it will convert one form to another .

It also state that in a chemical reaction  mass of matter can neither be created nor be destroyed.

 b) Ans : when barium chloride solution is mixed with sodium sulphate solution , I will be verified the law of conservation of mass that is we will observe that the total mass of reactant with apparatus is equal to the total mass of products with apparatus.

(7) Solution:

(a) Ans :  A gas can fill the whole vessels in which it is enclosed because The intermolecular space of gas molecules are very far with each other , when movement of gas  molecules occur it will collide with each other , it has not any fixed shape and volume  , they completely fill the gap of available vessels.

(b) Ans : Solid can not be compressed because solid molecules are closely packed each other , very strong intermolecular force of attraction and negligible intermolecular space ,  molecules of solid  not move freely.

(c) Ans : liquid can flow because the molecules of liquid are loosely packed and connect with weak force of attraction , more intermolecular space between them and molecules are capable to move freely.

(d) Ans : when magnesium is burnt in the air , there is increased in mass after the reaction because the oxygen used as reactant not considered  in this reaction.

(8) a) The change of solid into liquid is called ……

Ans : melting

Explanation:  (In this process solid state change to liquid state when it get heated or increase temperature pass their melting point)

(b) The process solid directly change into  gas is  called ……

And : sublimation

Explanation:  (when substance directly heated and change the solid state to gaseous state  not converted into liquid state is called sublimation)

(c) The change of water vapour into water is called ……

Ans : condensation

Explanation:  (When gas , steam or water vapour occur cooling environment it change form gasses state to liquid state )

(d) The temperature at which a liquid start changing into its vapour state is ……

Ans : boiling point

Explanation:  (When the temperature increase and liquid change into its vapour at fix temperature are known as boiling point for example boiling point of water is 100°C)

(9) Solution

a)  substance which sublime .

Ans :  The substance  ( Sublime ) which sublime example are following.

Examples : camphor ,  naphthalene , iodine , dry ice etc.

(b) substance do not change their state on heating .

Ans : The substance ( Gas ) do not change their state on heating examples are following.

Example : oxygen , Nitrogen , Hydrogen etc.

(10) Solution:

(a) Diffusion :

Two or more substances molecules intermix with each other through the randomly movement of molecules , to form homogeneous mixture is known as Diffusion .

(b) Brownian Motion :

Randomly movement of tiny or small particles suspended in liquid or gaseous are called Brownian motion . It is also called Brownian Movement.

(11) Solution:

Ans : When sodium chloride is added to a definite volume of water and stirred well , q solution is formed , there is intermolecular space between the water particles , in which salt particles get settle or adapted when it dissolved .

(12) Solution:

Ans : A  gas jar full of bromine vapour (reddish brown), another gas jar which is appear  empty is inverted over a gas jar containing bromine vapour ( reddish brown) . It is observed that after sometime  from the jar fill with bromine vapour transmitted or expand into upper  jar , this is because bromine vapour is mixing each other and expand. This phenomenon is diffusion . The rate of diffusion is faster in the gaseous state and slower in the solid state.

(13) Solution:

Ans : A piece of Chalk broken easily into smaller pieces while a coal piece can not be broken easily because chalk molecules have less or weak  intermolecular force of attraction while a coal pieces molecules have strong intermolecular force of attraction that’s why coal piece not be broken easily.

Updated: June 21, 2021 — 12:42 pm

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