1. Thermal Properties of Matter
Physics 2

2. Topic Outline
• Temperature
• Thermal expansion
• Boyle’s Law
• Charles’s Law
• Atoms and Molecules
• Kinetic Theory of Gases

3. Temperature
A temperature of a body of matter is a
measure of the average kinetic energy of
random translational motion of its constituent
particles.
It measures the hotness or coldness of a
body.

4. Thermometer
Thermometer is a device
used to measure
temperature.
In Celsius scale the freezing
point of water is 0oC and its
boiling point is 100oC, and in
the Fahrenheit scale, these
points are assigned the
values of 32oF and 212oF,
respectively.

5. Thermal Expansion
Thermal expansion is the change in length in
a solid because of the change in temperature.

6. Coefficients of Linear Expansions

7. Example:

8. Volume Expansion

9. Water
Above 4oC water expands
when heated. From 0oC to
4oC, however, the volume of a
water sample decreases with ice
increasing temperature. Thus
water has its maximum
density at 4oC.

10. Boyle’s Law
Discovered by Robert Boyle (1627‐1691), states that at
constant temperature, the volume of a gas is inversely
proportional to its absolute pressure.

11. Example:

12. Absolute Temperature Scale
The absolute temperature scale has its zero point at ‐273oC;
temperature un this scale are measured in Kelvin (K). The
Rankine absolute temperature scale has its zero point at ‐
460oF; temperature in this scale are designated oR. Absolute
zero is 0K = 0oR = ‐273oC = ‐460oF.

13. Charles’s Law
Discovered by Jacques Chares, states that at
constant pressure, the volume of a gas is
directly proportional to its absolute
temperature.

14. Example:

15. Ideal Gas Law

16. Atoms and Molecules
Elements are the simplest substances of which matter in
bulk is composed. The ultimate particles of an elements are
its atoms.
Two or more elements may combine chemically to form a
compound, a substance whose properties are different
from those of the elements that compose it.
The ultimate particles of a compound in gaseous form are
molecules, which consist of the atoms of its constituent
elements joined together in a definite way.
1 atomic mass unit = 1 u = 1.66 x 10‐27 kg

17. Example:

18. Kinetic Theory of Gases
According to the kinetic theory of gases, a gas consists of
a great many tiny individual molecules that do not
interact with one another except in collisions.
The molecules are supposed to be far apart compared
with their dimensions and to be in constant motion.

19. Kinetic Energy and Absolute
Temperature of gases
The significance of absolute zero in the kinetic theory of gases is
straight forward: It is the temperature at which all molecular
translational movement stops.

20. Molecular Speeds
Finding the average speed of gas molecules
whose mass is m.

21. REFERENCE:
Modern Technical Physics 6th Edition by
Arthur Beiser
Copyright © 1992 by Addison‐Wesley
Publishing Company, Inc.