Page 163 - text book form physics kssm 2020

Chapter 4
Heat
Example 1

3
An air bubble has a volume of 1.2 cm at a temperature of 27°C. What is the volume of the
air bubble if its temperature increases to 47°C?
Solution:
3
14243
1
Step V = 1.20 cm
V = Final volume of air
2
List the given information T = (27 + 273) = 300 K
1
in symbols. T = (47 + 273) = 320 K
2
14243 V V
Step Gas pressure is constant.
Charles’ Law formula is used.
Identify and write down the
formula used. T 1 1 = T 2 2

V
1.2
2
Step 300 = 320
Substitute numerical values into 1.2 × 320
the formula and perform the 1442443 V =
2
300
calculations. = 1.28 cm 3

Relationship between Pressure and Temperature of Gas

Photograph 4.6 shows air pressure in the tyre of a car being measured on a hot day. Th e driver of
the car touched the tyre aft er the journey and found that the tyre is hotter than before the journey.
Photograph 4.7 shows the readings of the pressure gauge before and aft er the journey. What
happened to the air pressure inside the tyre?

(a) Before journey) B f j
(

(b) After journey
Photograph 4.6hotograph 4.6 Air pressure of tyre being measured Air pressure of tyre being measured (b) Aft j
P
Photograph 4.7hotograph 4.7 Readings of air pressure Readings of air pressure
P
157
157
4.4.3 4.4.4 157
4.4.3
4.4.4