Class 9 SCI CH 1 - Session 3

2. Matter in Our
Surroundings

3. Important Questions
and Answers

4. 1. A form of matter has no fixed shape
but it has a fixed volume. An example
of this form of matter is
(a) Sodium
(b) Kerosene
(c) Carbon steel
(d) Carbon dioxide
Ans : Kerosene

5. 2. Which one of the following statements is not
true?
(a) The molecules in a solid vibrate about a
fixed position
(b) The molecules in a liquid are arranged in a
regular pattern
(c) The molecules in a gas exert negligibly
small forces on each other, except during
collisions
(d) The molecules of a gas occupy all the space
available
Ans: (b) The molecules in a liquid are
arranged in a regular pattern

6. 3. The property of flow is unique to
fluids. Which one of the following
statements is correct?
(a) Only gases behave like fluids
(b) Gases and solids behave like
fluids
(c) Gases and liquids behave like
fluids
(d) Only liquids are fluids
Ans: Gases and liquids behave like fluids

8. Convert 90oC to oF
oF = (9/5)oC + 32
= ((9/5) x 90) + 32
= 194 oF

9. Convert 293 K to oC
oC = K – 273
= 293 – 273
Ans: = 20 oC

10. Convert 392 oF to oC
oC = (F – 32) x 5/9
= (392 – 32) x 5/9
= 200 oC

11. Kelvin (K), base unit of thermodynamic
temperature measurement in the International
System of Units (SI)
The Kelvin temperature scale is used by
scientists because they wanted a
temperature scale where zero reflects the
complete absence of thermal energy.
What is Kelvin Scale? Why do
scientists use this scale?

12. Ans:
When a person has fever, his body temperature
becomes more than the normal body
temperature. If we put strips of wet cloth on
the forehead of a person suffering from high
fever, the water evaporates taking heat from
the body. Thus, moist strips will lower his body
temperature.
Why do the doctors advise to put strips of wet
cloth on the forehead of a person having high
fever?

13. Evaporation is the process by which
water changes from a liquid to a gas
or vapor.
What is Evaporation?

14. Ans:
A liquid has a larger surface area in a saucer
than in a cup. Thus, it evaporates faster and
cools faster in a saucer than in a cup. For this
reason, we are able to sip hot tea or milk
faster from a saucer than a cup.
Why are we able to sip hot tea or milk faster
from a saucer than a cup?

15. Ans:
The earthen pot is porous with lot of pores on it, the
water oozes out through these pores and the water
gets evaporated at the surface of the pot thereby
causing cooling effect. This makes the pot cold and
the water inside the pot cools by this process.
How does the water kept in an earthen pot
(matka) become cool during summer?