Internal energy. Energy of the system is named thermal internal energy that relies on its thermodynamic state only. For a system, on which the external forces are not acting and which is found in a state of macroscopic peace, the thermal internal energy is a complete energy of the system. In simple case the internal energy of the system is equal to the difference between a complete energy and sum of kinetic and potential energy.

Internal energy of homogeneous system is an additive value. She is calculated as a sum of internal energies of all its macroscopic particles, in other words, she is proportional to the mass of the system.

Internal energy of the heterogeneous system is folded not from the sum of energies of all homogeneous particles of the system, but also includes the forces of molecular interaction between their surface’s layers.

 Internal energy of ideal gas relies only on his absolute temperature and is proportional to the mass of the body.

Internal energy of mixture of ideal gases is equal to the sum of internal energies of the component gases.

In more general case Internal energy of body consists of the energy of chaotic thermal motion of all microparticles (molecules, atoms and ions), energies of interaction of these particles, energies of electronic shells of atoms and ions, intranuclear energy.

The forces of interaction between molecules. In the concept of a space it is defined that one substance of world can not affect other, without influencing from them. The forces of the interaction of molecules in the nature are the electric forces which are acting between the charged particles – electrons, atomic nucleus that enter in the atoms. So as the molecules consist of a plenty of the charged particles, the forces of their interaction can be counted up only approximately.

It is approximately possible to consider that the forces of interaction between molecules rely on the distance r between the centers of the masses of molecules. On the distances 10-9 m the attractive forces are acting, and on the distances 10-10 m – the repulsive one. The force of intermolecular action F is the resultant of attractive and repulsive forces.

It is known from experiments and theoretical researches: F(r) = - a/ r7 at r > r0; F(r) = 0 at r = r0; F(r) = b/rm at r < r0.

The value r = r0, at which the attractive and repulsive forces are counterbalanced, determines the most stable disposing of molecules. The coefficient’s values a and b rely on the structure of molecules. The repulsive forces (r < r0) decrease more fast than attractive (r > r0) forces and can act in sufficient measure only at considerable rapprochement of molecules. The attractive forces, which decrease inversely proportional to the seventh degrees of distance between molecules F(r) = - a/ r7 at r > r0, are called the Van der Waals force,

The potential and kinetic energies of molecular interaction. The interacting molecules are characterized by potential energy U(r), which is determined by the work which it is necessary to execute by the forces F(r) at the change of distance from the set value to the infinity, of distances where it is considered, that U(r) = 0. If two molecules are drawn together on distance Δr, the work, that is executed is evened ΔA = F(r) Δr and is positive. The growth of kinetic energy of molecules is accompanied by reduction of their potential energy in accordance with the law of conservation of energy. In this case potential energy has the negative value. If two molecules are drawn together on distance Δr in a region of the acting of repulsive forces, the system executes negative work ΔA < 0, which is expended on the overcoming of the repulsive forces.

The kinetic energy diminishes - potential energy grows and is positive. When all kinetic energy will go on implementation of work against the repulsive forces, the molecules will be drawn together on the smallest distance r = d, In the case the potential energy of two molecules will be equal to the complete energy of the system from two molecules E = U(d), the greater is a kinetic energy of molecules, the less is d. At r = r0 (that corresponds to the relation F(r) = 0), the potential energy has a minimum and the system, which consists from two molecules, has a stable equilibrium. The correlation between the value U(r0) and a middle kinetic energy of molecule Ek is different for the different aggregate states of substance: Ek » U( r ) for gases; Ek ≈ U(r0) for a liquid; Ek < U(r0) for a solid.

A distance d determines the size of region, in which the second molecule can not penetrate, and is named the effective diameter of molecule.

The thermal motion and the kinetic energy of molecules. The molecules of all substances are found in the permanent thermal motion and posses by kinetic energy. The character of this motion relies on the aggregate state of substance.

In the gases there is almost no interaction between molecules so they posses by large kinetic energy. In the intervals between the collisions they move rectilinearly.

In liquids the kinetic energy of molecules is practically equal to their potential energy, therefore a motion of molecules is complicated. They hesitate round the instantaneous equilibrium of the state, which is changed in time. Thus in a liquid there is a close order, in other words, there is the well-organized disposing of only neighboring molecules. The vibrations of molecules in the relation to position of the instantaneous state of equilibrium are limited by some volume that is equal to the free space to the neighboring molecules. A distance, on which the position of the state of equilibrium is displaced for some time τ, is equal to the middle distance between the molecules (10-10 m). These displacements are jump-like. The energy that is expended on these jumps is used to overcome the forces of interaction with the other molecules. With the growth of temperature the time τ is diminished.

Most solids that meet in nature are crystals, in other words, they have the well-organized disposition of molecules that is periodically repeated in spacious. These particles create a crystalline grate in spacious. In the solids the attractive forces of molecules do not allow them to be removed on large distance from position of the state of equilibrium. In crystals a distant order is realized, in other words, well-organized disposition in relation to any particle within the limits of large volume in comparison with the distances between the molecules.

Brownian motion is a proof of existence of thermal motion of molecules of substance. The chaotic continuous motion of very small particles, which are balanced in a liquid or gas, is called Brownian. The Brownian particles must to be very small, that the attractive force did not affect their motion. The reason of the Brownian motion of particles is the unregulated blows of the molecules of substance in these particles.

The transfer processes. The physical kinetics or microscopic theory of processes studies the processes that flow in the unstable systems (transfer of substance, energy and impulse). At violation of equilibrium the system tries to get back to this state. In this system the transfer processes appear, which are related with the streams of heat, electric charges and etc. To such processes belong: diffusion, thermal conductivity and internal friction (viscosity).

The process of penetration of two or greater amount of substances that touch one in the other is called diffusion. Diffusion is observed in one substance, if she is heterogeneous. Thus the smoothing of concentration of particles in unit of volume (in the different parts of substance) passes. At diffusion the molecules are displaced from those parts of body, where their concentration is greater, in those parts, where their concentration is smaller. The physical reason of the phenomenon of diffusion consists in the thermal motion of molecules. The diffusion is observed in gases, liquids and solids. Its velocity relies on a temperature. 

If different parts of the substance (space) have a different temperature, in such environment a thermal stream appears. A thermal stream flows in a direction of decrease of temperature. Direction of Thermal conductivity coincides with the direction of distribution of heat.

At motion of layers of liquid or gas with a different velocity the force of internal friction appears between them. In accordance with the 2nd law of Newton at the interaction of two layers for a unit of time the impulse transfer occurs that is characterized by dynamic viscidity. The physical essence of Dynamic viscosity – she is quantitatively equal to an impulse that is carried from one layer to the other through the unit of area for a unit of time at the velocity gradient even to a unit.

The thermal motion and the kinetic energy of molecules of gaseous (air) can be used to create Fast Air Molecules Induced Current (FAMIC) generators that are based on ionization of molecules and atoms of solid under action of rapid particles of air and the use of the directed motion of the ionized particles in solid for production of current.

Surface energy of particles that arises up in the surface layer of liquid in comparison with their energy inside the volume of phase can be utilized to build new type of engine for hydroaccumulation and electric power production. This artificial molecular hydropower system developed by the team of Nizhyn Laboratories of Scanning Devices uses for its work the energy of surface tension that appears on the boundary of two phases (liquid and solid) as a result of molecular interaction in contiguous tangent phases.  

By Vasil Sidorov on October 18, 2009 in Queltanews.com

sidorovvasil@gmail.com