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The British scientist James Clerk Maxwell and the Austrian physicist Ludwig Boltzmann, in the 19th century, led the development of the theory, which became one of the most important concepts in modern science.
In General the simplest kinetic model is based on the assumption that:
(1) A gas is composed of a large number of same molecules moving in different direction, separated by large distances relative to their size;
(2) Molecules undergo a perfectly elastic collision (not do energy loss) with the walls of the container, but do not interact.
(3) Kinetic energy transfer between the molecules is known as heat. This assumption makes it easier to bring the features of gases within the mathematical treatment range.
Such a model defines perfect gas and is a reasonable approximation to real gas, especially at the limit of extreme dilution and high temperature.
Based on the kinetic theory of gases, the pressure on the walls of the containers may be specified to the degree of random collision of the molecules depending on the temperature of the gas. In General the Gas pressure can therefore be directly related to temperature and density. Many other gross properties of gaseous substances can be derived, such as viscosity, thermal conductivity, diffusion, Heat capacity, and mobility.
In order to explain the observed deviations from perfect gas behaviour, such as condensation then the assumption must be appropriately modified. In doing so, considerable insight has been gained as to the nature of molecular dynamics and interaction.
Assumption of Kinetic Theory of Gases
There are Certain Assumption of Kinetic Theory of Gases:
- In General the gas contains very small particles. This small size of particles is such that the sum of the volume of the individual gas molecules is negligible as compared to the volume of the container of gas. This is equal to stating that the average distance separating the gas particles is large compared to their size.
- In General the number of particles is so large that the mathematical treatment of the problem is well justified. This thinking is sometimes called the thermodynamic limit.
- The Fast-moving particles constantly collide between themselves and the walls of the container. All of these collisions are perfectly elastic, which means the molecules are perfect hard spheres.
- Unless there is a collision, the interaction between molecules is negligible. They exert no other forces on one another.
Degree of Freedom
In General, Degree of freedom is defined as the number of possible independent ways in which the position of a system can be changed.
Conclusion
This topic includes the kinetic theory of gas and tries to explain it.
Microscopic feature of a gas in terms of motion of its molecules. The gas is assumed to contain a large amount of same, different particles called molecules, the molecule being the smallest unit having the same chemical properties as the substance.
The Elements of kinetic theory were developed by Maxwell, Boltzmann and Clausius between 1860-1880’s. Kinetic theories are available for gas, solids and liquids. However this chapter discusses gas kinetic theory of gases only.
