Kinetic energy is the energy that is determined by the speed of the various points that belong to this system.Thus it is necessary to distinguish between energy which characterizes the translational movement and rotational movement.Thus, the average kinetic energy - this is the average difference between the total energy of the entire system and its rest energy, that is, in essence, its magnitude is the average of the potential energy.
Its physical quantity calculated by the formula 3/2 kT where marked: T - temperature, k - Boltzmann constant.This value can serve as a criterion for comparison (benchmark) for the energy contained in various types of thermal motion.For example, the average kinetic energy of the gas molecules in the study of translational motion, is 17 (- 10) nJ at a gas temperature of 500 C. As a rule, the greatest energy in the forward movement of the electrons possess, but the energy of neutral atoms and ions is much smaller.
This value, if we consider any solution gas or liquid, kept at this temperature has a constant value.This statement is true for colloidal solutions.
situation is somewhat different from the solids.In these substances, the average kinetic energy of any particle is too small to overcome the forces of molecular attraction, but because it can only make some movement around the point which conditionally fixes a certain equilibrium position of a particle over a long period of time.This property allows the solids to be sufficiently stable in shape and volume.
If we consider the conditions: forward movement and ideal gas, there is the average kinetic energy is not a value dependent on the molecular weight, and therefore defined as the value is directly proportional to the absolute temperature.
All these judgments we have given with the intention to show that they are valid for all types of aggregation states of matter - in any of these temperature serves as the main characteristics, reflecting the dynamics and intensity of thermal motion of the elements.And this is the essence of the molecular-kinetic theory and content of the concept of thermal equilibrium.
As you know, if the two physical bodies come into contact with each other, between them there is a heat exchange process.If the body is a closed system, that is, does not interact with any of the bodies, its heat transfer process will last as long as necessary to equalize the temperature of the body and the environment.This state is called the thermodynamic equilibrium.This conclusion has been repeatedly confirmed by experimental results.To determine the average kinetic energy, should refer to the characteristics of the temperature of the body and its heat exchange properties.
It is also important to consider that micro-processes within the body, and does not end when the body comes into thermal equilibrium.In this state, the movement takes place inside the body of molecules change their velocities, shocks and collisions.Therefore, it performed just one of several of our assertions - the volume of the body, the pressure (in the case of gas) may vary, but the temperature will still remain constant.This once again confirms the statement that the average kinetic energy of the thermal motion in isolated systems is determined solely by the temperature indicator.
This law established in the course of experiments Jean Charles in 1787.Through experiments, he noticed that the heating bodies (gases) by the same amount, the pressure of changes in accordance with the directly proportional law.This observation made it possible to create many useful devices and items, in particular - the gas thermometer.
