Thermal processes in nature are studied by the science of thermodynamics. It describes all the energy transformations taking place through such parameters as volume, pressure, temperature, ignoring the molecular structure of substances and objects, as well as the time factor. This science is based on three basic laws. The last of them has several formulations. The most commonly used in the modern world is the one that received the name "Planck postulate." This law is named after the scientist who brought it out and formulated. This is Max Planck - a vivid representative of the German scientific world, a theoretical physicist of the last century.
First and second beginnings
Before formulating Planck's postulate, let us first briefly introduce two other laws of thermodynamics. The first of them states the complete conservation of energy in all systems isolated from the outside world. Its consequence is the denial of the possibility of doing work without an external source, and therefore the creation of a perpetual motion machine that would work in this way (that is, the first kind of VD).
The second law says that all systems tend to thermodynamic equilibrium, while heated bodies transfer heat to colder ones, but not vice versa. And after equalizing the temperatures between these objects, all sorts of thermal processes cease.
Postulate Planck
All of the above applies to electrical, magnetic, chemical phenomena, as well as processes occurring in outer space. Nowadays, thermodynamic laws are of particular importance. Already, scientists are working intensively in an important direction. Using this knowledge, they seek to find new sources of energy.
The third statement concerns the behavior of physical bodies at extremely low temperatures. Like the first two laws, it gives knowledge about the basis of the structure of the universe.
The formulation of the Planck postulate is as follows:
The entropy of a correctly formed crystal of pure substance at zero temperature is zero.
This provision was introduced to the world by the author in 1911. And in those days caused a lot of controversy. However, the subsequent achievements of science, as well as the practical application of the provisions of thermodynamics and mathematical calculations proved its truth.
Absolute temperature zero
Now let us explain in more detail what is the meaning of the third law of thermodynamics, based on Planck's postulate. And let's start with such an important concept as absolute zero. This is the lowest temperature that the bodies of the physical world can only have. Below this limit, according to the laws of nature, it cannot fall.
In Celsius, this value is −273.15 degrees. But on the Kelvin scale, this mark is considered to be the origin. It is proved that in this state the energy of the molecules of any substance is zero. Their movement is completely stopped. In a crystal lattice, atoms occupy a clear, unchanged position at its nodes, not being able to even oscillate slightly.
It goes without saying that under the given conditions all thermal phenomena in the system also cease. The state of the regular crystal at absolute temperature zero also broadcasts Planck's postulate.
Clutter measure
We can know the internal energy, volume and pressure of various substances. That is, we have all the chances to describe the macrostate of this system. But this does not mean the opportunity to say something specific about the microstate of a certain substance. To do this, you need to know everything about the speed and position in space of each of the particles of matter. And their number is impressively huge. Moreover, under ordinary conditions, the molecules are in constant motion, continuously collide with each other and fly apart in different directions, changing direction in every fraction of an instant. And their behavior is dominated by chaos.
To determine the degree of disorder in physics, a special quantity called entropy is introduced. It characterizes the measure of unpredictability of the system.
Entropy (S) is a thermodynamic state function that serves as a measure of the disorder (disorder) of a system. The possibility of occurrence of endothermic processes is due to a change in entropy, because in isolated systems the entropy of a spontaneously proceeding process increases ΔS> 0 (the second law of thermodynamics).
Perfectly structured body
The degree of uncertainty in gases is especially great. As you know, they do not have shape and volume. At the same time they are able to expand indefinitely. Gas particles are the most mobile, because of this their speed and location have the greatest unpredictability.
A completely different thing is solids. In the crystalline structure, each of the particles occupies a certain place, making only some oscillations from a certain point. It is not difficult here, knowing the position of one atom, to determine the parameters of all the others. With absolute zero, the picture becomes completely obvious. This is evidenced by the third law of thermodynamics and Planck's postulate.
If a similar body is raised above the ground, the trajectory of movement of each of the molecules of the system will coincide with all the others, moreover, it will turn out to be predetermined and easily determined. When the body, when released, falls down, the indicators will immediately change. Particles will acquire kinetic energy from hitting the ground. It will give an impetus to thermal motion. This means that the temperature will increase, which will no longer be zero. And then entropy will arise as a measure of the disorder of a chaotically functioning system.
Features
Any uncontrolled interaction provokes an increase in entropy. Under ordinary conditions, it can either remain constant or increase, but not decrease. In thermodynamics, this is a consequence of its second law, already mentioned earlier.
Standard molar entropies are sometimes called absolute entropies. They are not changes in entropy that accompany the formation of a compound from its free elements. It should also be noted that the standard molar entropies of free elements (in the form of simple substances) are not equal to zero.
With the advent of Planck's postulate, absolute entropy has a chance to determine. However, the consequence of this provision is also that in the nature of temperature zero according to Kelvin it is not possible to reach, but only as close as possible to it.
Mikhail Lomonosov was able to theoretically predict the existence of a temperature minimum. He himself purely practically achieved freezing of mercury to -65 ° Celsius. Nowadays, by means of laser cooling, particles of substances were brought almost to a state of absolute zero. More precisely, up to 10 -9 degrees on the Kelvin scale. However, even though this value is negligible, it is still not 0.
Value
The previously mentioned postulate, formulated by Planck at the beginning of the last century, as well as subsequent work in this direction of the author, gave a huge impetus to the development of theoretical physics, which resulted in its significant progress in many fields. And even a new science arose - quantum mechanics.
Based on the theory of Planck and Bohr's postulates, after some time, more precisely in 1916, Albert Einstein was able to describe the microscopic processes that occur during the movement of atoms in substances. All the developments of these scientists were later confirmed by the creation of lasers, quantum generators and amplifiers, as well as other modern devices.
Max plank
This scientist was born in 1858 in April. Planck was born in the German city of Kiel in a family of famous military, scholars, lawyers and church leaders. Even at the gymnasium, he showed remarkable abilities for mathematics and other sciences. In addition to the exact disciplines, he studied music, where he also showed his considerable talents.
Entering the university, he chose theoretical physics for study. Then he worked in Munich. Here he began to engage in thermodynamics, presenting his work to the scientific world. In 1887, Planck continued his activities in Berlin. This brilliant scientific achievement belongs to this period, as the quantum hypothesis, the deep meaning of which people could only understand later. This theory was widely recognized and earned scientific interest only at the beginning of the 20th century. But it was thanks to her that Planck gained wide popularity and glorified his name.