• Thermal expansion
• Boyle’s Law
• Charles’s Law
• Atoms and Molecules
• Kinetic Theory of Gases
A temperature of a body of matter is a
measure of the average kinetic energy of
random translational motion of its constituent
It measures the hotness or coldness of a
Thermometer is a device
used to measure
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,
Thermal expansion is the change in length in
a solid because of the change in temperature.
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.
Discovered by Jacques Chares, states that at
constant pressure, the volume of a gas is
directly proportional to its absolute
Atoms and Molecules
Elements are the simplest substances of which matter in
bulk is composed. The ultimate particles of an elements are
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
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.
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.
Finding the average speed of gas molecules
whose mass is m.