## The definition of an ideal gas

An ideal gas is a theoretical generalization, which is used by physicists for the analysis of probability theory. An ideal gas consists of molecules that repel each other and do not interact with the walls of the vessel. Inside an ideal gas there are no forces of attraction or repulsion between molecules, and energy is not lost during collisions. An ideal gas can be completely described with a few parameters: volume, density and temperature.

The equation of state for an ideal gas, commonly known as the Law of a perfect gas has the form:

PV = NkT.

In the equation N is the number of molecules k – Boltzmann constant, which is equal to about 14000 Joules per Kelvin. The most important is that pressure and volume are inversely proportional to each other, and directly proportional to temperature. This means that if the pressure be doubled, and the temperature does not change, the gas volume doubles. If the volume of gas will be doubled, and the pressure remains constant, then the temperature will increase twice. In most cases, the number of molecules in the gas is considered constant.

Collisions between gas molecules are perfectly elastic and some energy is lost. Between gas molecules there are electrostatic interaction forces. But for most situations the ideal gas law is as close to the real behaviour of gases. Formula the relationship between pressure, volume and temperature can help scientists to intuitively understand the behavior of gas.

## Practical application

The ideal gas law is the first equation that the students meet when studying gases at the lessons of physics or chemistry. The equation of van der Waals forces, which includes a few minor corrections to the basic assumptions of the law of a perfect gas is also an integral part of many introductory courses. In practice these differences are so small that if the ideal gas law is not applicable for this particular case, the equation of van der Waals forces will not satisfy the conditions exactly.

As in most sections of thermodynamics, the ideal gas is initially in equilibrium. This assumption is not true if the pressure, volume or temperature change. When these variables change gradually, such a state is called a quasistatic equilibrium and the computational error may be small. In the case when system parameters are changing in a chaotic fashion, the ideal gas model is not applicable.