Molecular-kinetic theory - it's all about minutiae

The assumption that everything in nature consists of the smallest particles was expressed by ancient Greek philosophers. This hypothesis remained unproven for a long time. All the study of the surrounding world and the behavior of physical bodies was based on a macroscopic approach. However, over time, the accumulated results of work on the study of nature and substances ceased to fit into the available theoretical concepts, and then scientists created the molecular-kinetic theory (MKT).

MKT explains the thermal phenomena and internal properties of physical bodies on the basis of the motion and interaction of ions, molecules and atoms, of which these bodies are built. In other words, the theory tries to explain macroscopic phenomena from the position of a microscopic approach. The main provisions of the molecular-kinetic theory are as follows:

1. The substance consists of separate particles - ions, atoms, molecules.
2. All particles move chaotically and constantly.
3. Particles always act on each other: attracted and repelled.

The first postulate, on which the molecular-kinetic theory is based, can be confirmed by simple observation in an electron microscope. Its capabilities make it possible to directly see atoms and molecules. These "bricks", of which the substance consists, do not fill the entire available space - they are located at a distance from each other. Another confirmation of the postulate may be an increase in body size when heated. Here, too, everything is clear - when heated, the distance between individual particles increases, and the body size increases.

The second provision of the MKT refers to chaotic and continuous movement. This position can be confirmed by Brownian motion and the phenomenon of diffusion. The cause of the Brownian motion are collisions between individual particles, and they are moving chaotically. And this can be considered an additional proof of the first position (the existence of atoms and molecules).

The phenomenon of diffusion is the mutual penetration of substances into each other. This is due to the chaotic motion of particles of matter. As the interaction time increases, the depth of penetration increases. It also depends on temperature and pressure.

As a confirmation of the third position of MKT, one can take the elasticity of bodies. When the body is stretched, the distances between individual particles of matter increase and gravitational forces begin to predominate, seeking to return everything to their original position. In contrast, the forces of repulsion prevail under compression.

Well, the argument supporting this, there are different states in which the substance can be. The change in the state of the substance is due to a change in the forces acting between the individual particles. The particles themselves remain unchanged.

If we return to the question of the appearance of MKT, then we can say that the foundations of the molecular-kinetic theory were laid in the works of MV Lomonosov. They were given an explanation of the basic properties of gases and the nature of heat. All his assumptions were proved and confirmed at the end of the 10th century.

The work of theoretical physicists at this time was established for the gas connection of macroscopic indicators (temperature, pressure, volume) with microscopic (the number, mass and velocity of molecules). Hence the name - the molecular-kinetic theory. It should be noted that the development of this theory has not stopped, continuing in our days. Now it is called statistical mechanics and describes the behavior of large volumes of atoms and molecules.

The explanation of what the molecular-kinetic theory is is given above. Its main provisions are described and the facts confirming the stated assumptions are given.