As you know, all substances in nature have their own state of aggregation, one of which is gas. Its constituent particles - molecules and atoms - are located at a great distance from each other. Moreover, they are in constant free movement. This property indicates that the interaction of particles occurs only at the moment of approach, sharply increasing the speed of the colliding molecules and their size. This gaseous state of the substance differs from solid and liquid.
The very word "gas" in Greek sounds like "chaos." This perfectly characterizes the movement of particles, which is actually random and chaotic. Gas does not form a specific surface; it fills the entire volume available to it. This state of matter is the most common in our universe.
The laws that determine the properties and behavior of such a substance are most easily formulated and considered using the example of a state in which the relative density of molecules and atoms is low. It has received the name "ideal gas." In it, the distance between particles is greater than the radius of interaction of intermolecular forces.
So, an ideal gas is a theoretical model of matter in which the interaction of particles is almost completely absent. The following conditions must exist for him:
Very small sizes of molecules.
There is no force of interaction between them.
Collisions occur as collisions of elastic balls.
A good example of such a state of matter can be called gases, in which the pressure at low temperature does not exceed atmospheric 100 times. They are classified as discharged.
The very concept of “ideal gas” has made it possible for science to build a molecular-kinetic theory, the conclusions of which are confirmed in many experiments. According to this doctrine, ideal gases are distinguished between classical and quantum.
The characteristics of the former are reflected in the laws of classical physics. The movement of particles in this gas is independent of each other, the pressure exerted on the wall is equal to the sum of the pulses that are transmitted by individual molecules during a collision in a certain time. Their energy in total is combined by individual particles. The work of an ideal gas in this case is calculated by the Clapeyron equation p = nkT. A striking example of this is the laws deduced by such physicists as Boyle-Marriott, Gay-Lussac, Charles.
If an ideal gas lowers the temperature or increases the particle density to a certain value, its wave properties increase. A transition to a quantum gas takes place, at which the wavelength of atoms and molecules is comparable to the distance between them. Two types of ideal gas are distinguished here:
The doctrine of Bose and Einstein: particles of the same kind have an integer spin.
Fermi and Dirac statistics: another type of molecule having a half-integer spin.
The difference between a classical ideal gas and a quantum gas is that even at absolutely zero temperature, the energy density and pressure are different from zero. They become larger with increasing density. In this case, the particles have maximum (another name - boundary) energy. From this point of view, the theory of the structure of stars is considered: in those of them in which the density is higher than 1-10 kg / cm3, the law of electrons is pronounced. And where it exceeds 109 kg / cm3, the substance turns into neurons.
In metals, the use of a theory in which a classical ideal gas transforms into a quantum gas allows one to explain most of the metallic properties of a state of matter: the denser the particles, the closer to ideal.
At pronounced low temperatures of various substances in liquid and solid states, the collective motion of molecules can be considered as the work of an ideal gas, represented by weak excitations. In such cases, the contribution to the energy of the body that the particles add is visible.