DELHI PUBLIC SCHOOL BANGALORE - EAST
CHEMISTRY
MATTER IN OUR SURROUNDINGS
NAME: CLASS:IX SEC: DATE:
DIRECTION: In the following questions, a statement of assertion (A) is followed by a
statement of reason (R). Mark the correct choice as:
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of
assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of
assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
1. Assertion : The conversion of a gas directly into solid is called condensation.
Reason : Naphthalene leaves no residue when kept in open for some time.
2. Assertion : At normal pressure (1 atm) the boiling point of water is 1000 C or 373.15 K.
Reason : As the pressure increases, boiling point of water also increases.
3. Assertion : The intermolecular forces in solid state are stronger than those in the liquid state.
Reason : The space between the particles of matter is called intermolecular space.
4. Assertion : There is no change in the temperature of a substance when it undergoes a
change of state though it is still being heated.
Reason : The heat supplied is absorbed either as latent heat of fusion or as latent heat of
vaporisation.
Choose the correct option
5. Rate of evaporation of an aqueous solution decreases with increase in
(a) wind speed (b) temperature (c) humidity (d) surface area
6. Which of the following indicates the relative randomness of particles in the three states of
matter?
(a) Solid > Liquid > Gas (b) Liquid < Solid < Gas
(c) Liquid > Gas > Solid (d) Gas > Liquid > Solid
7. Some crushed ice is put in a test tube and warmed. The ice melts because its particles
(a) change their size
(b) gain heat energy and escape
(c) gain heat energy and become closer
(d) gain heat energy and move away from their fixed positions
8. The diagrams show the arrangement of particles of a substance at temperatures 200C and 400C
What are the likely melting and boiling points of the substance?
(a) -120Cand 350C (b) -250C and 450C
(c) -980C and 1000C (d) 440C and 800C
2
9. Give the temperature at which water exists in two different phases/states.
10. Why is Kelvin scale of temperature regarded as better scale than Celsius?
11. Solids are generally very heavy while gases are light. Explain.
12. Ammonia and hydrogen chloride gases are released from the two opposite corners in a room.
Which gas will reach first to a person sitting at the centre of the room?
13. Do we sweat more on a dry day or a humid day? Why?
14. Why is cooling caused by evaporation?
15. Why does the temperature of a substance remain constant during its melting point or boiling
point ?
16. A piece of chalk can be broken into small pieces when hammered but it is not possible in case of
iron bar. Why?
17. Convert the following temperature to the Celsius scale.
a. 200 K b. 450 K.
18. What will happen to inter particle spaces if a liquid is heated?
19. A sample of water under study was found to boil at 102 0C at normal temperature and pressure.
Is the water pure? Will this water freeze at 0 0C? Comment.
20. Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing
out of the spout of the kettle. She wondered whether the temperature of the steam was higher
than that of the water boiling in the kettle. Explain.
21. 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.
22. A student heats a beaker containing ice and water. He measures the temperature of the content of
the beaker as a function of time. Which of the following fig. would correctly represent the
result? Justify your choice.
23. Why do surgeons often spray some ether on skin before performing minor surgery?
24. The melting point of two solids A and B are 300 K and 350 K respectively. Which has more
inter particle forces?
25. It is seen that temperature of the remaining liquid drops when evaporation takes place from its
upper surface. Give reason
26. Why is water liquid at room temperature?
Answers
Answer:
1st :- A
2nd :- B
3rd :- A
4th :- C
5th :- C
6th :- A
7th :- C
8th :-
9th :- 100°C
10th :-
11th:- Due to the intermolecular spaces
12th :- Ammonium
13th :- Due to heat / ray which fall on our body
14th :-
15th :-
Answer:
1. (d) Assertion (A) is false but reason (R) is true.
2. (d) Assertion (A) is false but reason (R) is true.
3. (b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of
assertion (A).
4. (a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of
assertion (A).
5. (c) humidity.
6. (d) Gas > Liquid > Solid
7. (d) gain heat energy and move away from their fixed positions
8. …
9. 273 K & 373 K
10. Because it has no negative value..( -273 K is not possible on earth.)
11. Solids poses a large intermolecular attraction and they are rigid, they have no intermolecular space. Whereas gaseous poses intermolecular attraction less than solids and there have more intermolecular space and they are stated as fluid.
12. When ammonia and HCl gas are released from the two opposite corners of a room, then molecules of ammonia gas will reach faster to the person sitting in the centre of the room.
13. We sweat more on a humid day, because on humidity the amount of water vapour present in the atmosphere is more and therefore our body sweat is not able to vaporise into the gaseous state.