CBSE Class 9 Chemistry The Matter In Our Surroundings Worksheet

CBSE Class 9 Chemistry The Matter In Our Surroundings

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Q.1 Camphor disapperars without leaving any residue. Explain?

Ans. Camphor disappears without leaving any residue because

of sublimation, as it changes its state

directly fromsolid to gas without changing to liquid.

Q.2Why do we feel cool when we touch a piece of ice?

Ans.We feel cool because the temperature of ice is 0 deg C and our body's temp is higher than 0 deg

C.

Q.3 Convert the following:

a) 573 K

Ans. 573-273= 300 deg

b) 36 deg C

Ans. 273+36 = 309 K

c) 373 deg C

Ans. 373+273= 646 K

Q.4 Both the process of evaporation and boiling involves the change of state fromliquid to gas but

still they are different from each other. Justify.

Ans. Evaporation is different fromboiling as evaporation is a natural phenomenon, occurs on the surface

of the water and also it is a slow process whereas boiling is an artificial phenomenon , it occurs in the bulk of liquid

and is a fast process

Q.5Why is Kelvin considered as the best scale for measuring the temperature?

Ans. Kelvin is the best scale for measuring the temperature because it has no max temp. and it can

measure temperature to any extent.

Q.6 How can you show that evaporation causes cooling?

Ans.When we put some acetone on our hand , after sometime we will feel coolness on our hand because

the action absorbs kinetic energy fromour hand & evaporates and evaporation causes cooling.

Q.7What is the significance of boiling point & melting point of a substance?

Ans. The significance of boiling point and melting point is that it shows the

purity of the substance.

Q.8When we put CuSO4 in water, after sometime we find the soln. turns blue.Why? Also, on heating it

what change will occur?

Ans. The solution turns blue because of diffusion. On heating the solution nothing will happen.

Q9.How can you justify that table is a solid?

Ans.When we apply force on the table it doesn't change its shape because its intermolecules are tightly

packed , this shows that table is solid.

Q.10 Arrange the following in decreasing order of force of attraction:Water, Salt, Oxygen,

Also, state the reason.

Ans. Salt,Water, Oxygen

Exam Questions NCERT Class 9 Science Chapter 1 Matter in Our Surroundings

Question Give state of a matter if this substance has neither a fixed shape nor a fixed volume.
Ans : Gas.

Question Why cannot you smell its perfume at a short distance when incense stick is not lighted?
Ans : The particles of the perfume (matter) do not have sufficient energy to drift through the air. Thus, we cannot smell it at a few steps away from incense stick.

Question Why a rubber band is considered as a solid?
Ans : We can regard rubber band as a solid, because it regains its shape when the stretching force is removed from it.

Question. Predict the physical state of melting point of a substance is below the room temperature.
Ans : Ice.

Question. What do you mean by vapour?
Ans : A substance that is found in gaseous state only at room temperature is called vapour.

Question Why is the smell of the perfume of incense stick filled the whole room in few minutes, when lighted?
Ans : When the incense stick is lighted, the heat energy makes the particles of the perfume to move rapidly.
Thus, they easily drift through the air in the room and hence, we can smell it anywhere in the room.

Question What do you observe when force is applied and then removed on the plunger of the syringe containing air? Give a reason for your answer.
Ans : The plunger moves downward on the application of force to a considerable length. The plunger move backward and takes its original position when the force is removed.
The gases have large intermolecular spaces. So, they easily get compressed on the application of force.
The compressed gases are under high pressure. When the force is removed, this high pressure forces the plunger back to its original position.

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