Class: IX
Subject: Science
Topic:√Matter in our surroundings
No. of Questions: 20
1. Give reasons for the following observation:
the smell of hot sizzling food reaches you several metres away, but to get the smell from
cold food you have to go close.
ia
2. Give an account of the classification of matter.
ns
Ans: Solids diffuse at a very slow rate. But, if the temperature of the solid is increased, then
the rate of diffusion of the solid particles into air increases. This is due to an increase in the
kinetic energy to solid particles. Hence, the smell of hot sizzling food reaches us even at a
distance, but to get the smell from cold food we have to go close.
kI
IT
Ans: The important type of classification of matter is homogeneous and heterogenous
materials.
Homogeneous materials are divided into two types:
(i)
Homogeneous mixture (solutions)
(ii)
Pure substances.
Pure substances are of two types- elements and compounds. Elements are classified
as metals, non-metals and metalloids.
as
3. What are the two ways in which the physical state of matter can be changed ?
Ans: Melting and boiling are two ways in which the physical state of matter can be changed.
4. Define the term volatile Liquid.
Ans: Those liquids which can change into vapours easily are termed as volatile liquids.
5. Which of the following is accompanied by cooling?
Page|1
A.
B.
C.
D.
Vaporization
Evaporation
Condensation
None of these
Ans (b)
6.
A drop of Dettol got evenly distributed in water. How ?
Ans: This is because there is enough space between the particles of water and Dettol
particles gets into the spaces between the particles of other matter (water).
ns
7. When ink overflows from a fountain pen, we use blotting paper to remove excess of ink on
the paper. Why?
ia
Ans: Because ink (liquid) diffuses into the blotting paper, paper, we use blotting paper to
remove excess of ink on the paper from a fountain pen.
IT
8. Convert the following temperature to Celsius scale:
(a) 300 K
(b) 573 K
Ans: (a) 300 K = 300- 273 = 27 oC (b) 573 K = 573 – 273 = 300 oC
as
kI
9. At a pressure of 2 atmosphere a fixed mass of hydrogen occupies a volume of 8 litres. What
pressure must be maintained if the volume is to be increased to 10 litres, temperatures
remaining constant ?
Ans: P1= 1520 mm of Hg , P2 = ?
V1 = 8 L , V2 = 10 L
Applying Boyle’s Law, P1V1 = P2 V2
Substituting the values 2 x 8 = P2 x 10
P2 =
= 1216 mm of Hg
The pressure that must be maintained = 1216 mm of Hg
10. After rains why do rain drops dry away easily – on a cloudy day or on a sunny day ? State
reason also.
Page|2
Ans: Rain drops will dry easily on a sunny day. As the temperature is higher in sunny day,
evaporation increases. On a cloudy day temperature of the surrounding is low due to
humidity while on a sunny day the temperature of the surrounding is high. With an increase
of temperature, more number of particles get more kinetic energy to vaporize.
11. Which of the following statements is not correct?
A. The density of ice is less than the density of water.
B. To convert a temperature on the kelvin scale to Celsius scale, subtract 273 from the
given temperature.
C. To convert a temperature on the Celsius scale to kelvin scale, add 273 to the given
temperature.
D. Vaporization of a liquid causes cooling.
ns
Ans (d)
12. Why is motor oil more viscous than water ? Does motor oil have a greater surface tension
than water.
ia
Ans: In case of motor oil internal resistance between the layer of liquids is more in
comparison to water. Motor oil also has a higher surface tension.
Water, sugar, oxygen
kI
Ans: Oxygen < water < sugar
IT
13. Arrange the following substances in increasing order of intermolecular force of attraction :
as
14. Large volume of Compressed natural gas (CNG) is available in small cylinders to us due to
its property of –
A. High in flammability
B. Easy availability
C. High Compresibility
D. Low density
Ans: (C)
15. Which phenomenon occurs during the following changes?
(i) Size of naphthalene balls decrease.
(ii) wax melts in the sun.
(iii) drying of wet clothes.
Page|3
(iv) formation of clouds.
(v) Density of liquids is more than gases.
Ans: (i) Napthalene is sublime substance. Iit gets converted into gaseous form directly
without being first converted into liquid state. Thus the size of naphthalene balls decreases
automatically due to sublimation.
(ii) Wax is a solid it absorbs heat energy from sun and starts melting.
(iii) Wet clothes absorb heat energy from sun and water molecules evaporates off to
atmosphere.
ns
(iv) Water vapours formed from ocean and other water bodies of earth when reaches up to
atmosphere there they got cooled up and release their energy and undergoes condensation
to form clouds.
ia
(v) In comparison to gases, in liquids the molecules are close to each other. Therefore,
density of liquids is higher than that of gaseous state.
Ans (A)
P1 V2 T1 T1.d1
 x 
P2 V1 T2 T2 .d 2
as
d1 1 T1 2
 , 
d 2 2 T2 1
kI
IT
16. Densities of two gases are in the ratio 1 : 2 and their temperatures are in a ratio 2 : 1, then
the ratio of their respective pressures is
A. 1 : 1
B. 1 : 2
C. 2 : 1
D. 4 : 1
P1 2 1 1
 x 
P2 1 2 1
17. Why we close the bottle of nail polish remover immediately after using it?
Ans: Nail Polish remover contains acetone which has a high rate of evaporation . To stop the
evaporation of acetone. We have to close the bottle immediately after using it.
18. What are super cooled liquids?
Ans: Amorphous solids in which constituent particles are arranged in haphazard manner.
They resemble liquids as there flow very slowly at room temperature and thus termed as
super cooled liquids.
Page|4
19. Which of the following will not sublime?
A. Camphor
B. Ammonium chloride
C. Bromine
D. Iodine
Ans: (C)
20. What change or changes in the state of a gas bring about each of the following effects ?
(a) the number of impacts per unit time on a given container wall increases.
(b) the average energy of impact of molecules with the wall of the container decreases. (c)
the average distance between gas molecules increases, (d) The average speed of molecules
in the gas mixture is increased.
as
kI
IT
ia
ns
Ans: (a) increase in temperature at constant volume or decrease in volume or increase in
pressure (b) decrease in temperature (c) increase in volume, decrease in pressure (d)
increase in temperature
Page|5