Selina Concise Class 7 Chemistry Chapter 1 Matter and it’s Composition Solution

Selina Concise Class 7 Chemistry Solution Chapter No. 1- ‘Matter and it’s Composition’ For ICSE Board Students.

1) Define ;

a) Matter :

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

2)

Answer :  Difference between mass and weight :

Sr.No.

Mass

Weight

1. Mass Of the substance is same everywhere. Weight varies according or change to the Weight.
2. Mass can be measured by ordinary balance Weight can be measured by spring balance.
3. Mass is expressed  in gram and kilogram. Weight is expressed in Newton’s
4. SI unit is Kg ( Kilogram) SI unit is N ( Newton)

3)

Answer :  Weight of object on moon = 1/6th of weight on earth .

Given;

Weight of object on earth = 6 N

weight of object on  moon× weight of object on earth

1/6 × 6  =   1N

Mass of object does not change with change in gravity,  because of this mass of object remain same on moon.

4)

a)

Answer  : When we put some marbles in glass which is a half filled water , we observed that the water level will increase in the glass and weigh of glass also increase ,  this happens because the marbles occupies space and also have mass.

b)

Answer : When ice is kept at room temperature , ice start will Melting and changefrom solid state to liquid state (water).

5)

Answer : Three main characteristics of the particles of matter are following .

1) Particles of matter are very small , it can neither be created nor be destroyed.

2) Particles of matter have space between them this space said that interparticular or intermolecular space.

3) The particles of matter are constantly moving .

4) Particles of matter attract each other.

6)

Answer :

Sr.No Atom Molecule
1) Atom is smallest entity of an element Molecule is smallest particle of an compound.
2) Atom does not present in free state except noble gases. Molecule present in free state.
3) Atom does not have a chemical bond. Molecules of atoms are attached together by chemical bond.
4) Example : hydrogen (H) , Nitrogen (N) , Oxygen (O) etc. Example : Water (H2O) , carbon dioxide (CO2) , sodium chloride (NaCl) etc.

7) a)

Answer :  Solid :

Solid have fixed shape and  volume , molecules packed closely by strong intermolecular force of attraction .

Example :  ice , rock , wood , etc.

b)

Answer : liquid :

Liquid have fixed volume but not a fixed shape of its own , molecules are loosely packed and has weak intermolecular force of attraction.

Example: Water , alcohol , oil , etc.

c)

Answer : Gas :

Gas has not fixed shape and fixed volume , molecules of are very far to each other and has weakest intermolecular force of attraction .

Example :  Carbon dioxide, Nitrogen , oxygen , water vapour etc.

8)

Answer : liquid and gasses called as fluid because liquid and gasses can flow , the molecules of liquid and gasses are loosely packed and attached with weak force of attraction , more intermolecular space between them and molecules are capable to move freely.

9)

a)

Answer : Interconversions of 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 .

b)

Answer :  Solid , liquid , and gasses are differ in their physical state because of the intermolecular force of attraction and intermolecular space between the molecules of solid, liquid and gas.

c)

Answer : Solid liquid and gas change their state to another one on  changing  temperature and pressure .

10)

a)

Answer : When a stone is dipped in a glass containing some water, the level of water rises  because stone occupies volume and it does not dissolved in water that’s why water level increase .

But when a spoon of sugar is added to water  and stirred,  the sugar dissolves and disappear in water but the water level does not rise because liquid state has intermolecular space between molecules,  liquid molecules far to each other  Due this in sugar solution sugar particles being smaller get adjusted between the water molecules.

b)

Answer : A drop of ink added to water in a glass tums whole water blue because the water and ink particles are constantly moving , due  to this movement  ink particles spread a over the glass water and whole water turn blue.

11) Fill in the blanks

a) Air is a matter because it has …………. , …………. And it can be ……………

Answer : weight , mass and compressed

(Air is a matter example of gases state which has mass and weight , air can be compressed under pressure )

b) The molecules are made up of …………….

Answer : atom

(The molecules are made up of atom, when two atoms are attached with each other by  electrostatic force or intermolecular force of  than  molecules are formed.)

c) The quantity of matter in an object it’s called …………………

Answer : mass

(the amount of  matter present in object is called mass  )

d) The state of matter have definite volume and definite shape is called………….

Answer : solid

(the matter which have fixed volume and shape , and strong intermolecular force of attraction , molecules are closely packed with each other are called solid state)

e) The substance which can flow are called………..

Answer : fluid

(A liquid and gas are called fluid because both the substance molecules are move freely and flow , So the substance which can flow are called fluid .)

12)

a)

Answer :  Melting

b)

Answer :  Intermolecular force of attraction

c)

Answer : atom

d)

Answer:sublimation

e)

Answer: condensation

13)

Answer :

Solid

Liquid Gases
Coal Kerosene

Oxygen

Wood

Milk

Water vapour

Wax

Blood

 

Sugar

   
Updated: August 6, 2021 — 12:03 am

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