According to this theory:
Temperature reflects the average kinetic energy: T
he higher the temperature of a substance, the greater the average kinetic energy of its particles. This is because temperature is directly proportional to the average kinetic energy of the particles in the substance.
Temperature and particle speed:
As temperature increases, the particles in a substance move faster on average. Conversely, at lower temperatures, particle motion slows down. This relationship between temperature and particle speed helps us understand how changes in temperature affect the behavior of substances.
Absolute zero
: According to the kinetic theory of gases, absolute zero is the temperature at which particle motion ceases entirely. At this temperature, particles have minimal kinetic energy, and their motion stops. Absolute zero serves as the zero point on the Kelvin temperature scale.
Temperature and pressure:
The kinetic theory also explains how changes in temperature can affect the pressure exerted by a gas. When the temperature of a gas increases, the average kinetic energy of its particles increases, leading to more frequent and forceful collisions with the walls of the container. This results in an increase in pressure.
Kinetic Theory: Consistent With Ideal Gas Equation and Gas Laws
It is consistent with the ideal gas equation:
For the kinetic gas equation:
E
N
=
3
2
k
B
T
EN=32kBT
E
=
3
2
N
k
B
T
E=32NkBT
For an ideal gas, its internal energy is directly proportional to the temperature. This depicts that internal energy of an ideal gas is only dependent on its temperature, not on pressure or volume.
When Kinetic theory is consistent with Dalton’s law of partial pressure:
The equation for kinetic theory:
P
=
1
3
nm
v
2
P=13nmv2
If a mixture of gases is present in the vessel, then:
P
=
1
3
[
n
1
m
1
v
1
2
+
n
2
m
2
v
2
2
+
.
.
.
]
P=13[n1m1v12+n2m2v22+...]
The average kinetic energy of molecules of different gases at equilibrium will be equal
1
2
m
1
v
1
2
=
1
2
m
2
v
2
2
=
3
2
k
B
T
12m1v12=12m2v22=32kBT
Then the total pressure will be:
P
=
1
3
[
3
2
n
1
k
B
T
+
3
2
n
2
k
B
T
]
P=13[32n1kBT+32n2kBT]
P
=
k
B
T
[
n
1
+
n
2
+
.
.
.
.
]
P=kBT[n1+n2+....]
P
=
R
N
A
[
n
1
+
n
2
+
.
.
.
.
]
P=RNA[n1+n2+....]
P
=
[
μ
1
+
μ
2
+
.
.
.
.
]
RT
P=[𝜇1+𝜇2+....]RT
P
=
P
1
+
P
2
+
.
.
.
.
.
P=P1+P2+.....
This is known as Dalton’s law of partial pressure.
Law of Equipartition of Energy: Degrees of Freedom
Degrees of freedom represent the independent ways a body or system can move, rotate, or vibrate. They are crucial in understanding the energy distribution of a system, as outlined in the Law of Equipartition of Energy. Here is the different types of degrees of freedom:
Translational Degree of Freedom
: This refers to the movement of the entire body from one position to another. For example, in a gas molecule, translational movement occurs when the entire molecule shifts its position in space.
The number of translational degrees of freedom depends on the dimensionality of the movement. In three-dimensional space, a molecule has three translational degrees of freedom (x, y, and z axes). In two-dimensional space, it has two degrees of freedom, and in a straight line, it has only one. In monoatomic gas molecules, which consist of a single atom, only translational degrees of freedom exist.
Rotational Degree of Freedom
: This refers to the independent rotations that specify a body's or system's orientation. In diatomic gas molecules, rotational degrees of freedom exist in addition to translational degrees.
For example, in a diatomic molecule like oxygen (O2), the rotation of one oxygen atom relative to the other adds rotational degrees of freedom. There can be rotations along different axes, contributing to the total rotational degrees of freedom.