27. Ideal gas in molecular-kinetic theory

The challenge of molecular-kinetic theory is to explain the properties of macroscopic bodies based on the laws of motion of the particles composing them. This challenge is quite complex. In this chapter we get to know the theory of the simplest system - the ideal gas.

Let's assume that the gas is fairly sparse, so that the distance between gas molecules is many times greater than their size. Highly sparse gas is called ideal in molecular theory. In thermodynamics, we called ideal such a gas, the equation of state of which is the Clapeyron equation \((1-12)\). The new definition of ideal gas does not contradict the old one, because the molecular-kinetic theory of gas leads to the equation of state \((1-12)\).

In the simplest model of gas molecules can be considered as very small solid elastic balls, the attraction forces between them are absent, and the repulsive forces appear only when the molecules collide directly with each other or with the molecules of the vessel walls. In such a model, the motion of gas molecules is subject to the laws of classical Newton mechanics.