Thermal processes in nature are studied by the science of thermodynamics. It describes all the ongoing energy transformations using 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's postulate". This law is named after the scientist who deduced and formulated it. This is Max Planck, a bright representative of the German scientific world, a theoretical physicist of the last century.
First and second beginnings
Before formulating Planck's postulate, let's first get acquainted briefly with the other two laws of thermodynamics. The first of them asserts 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 hence the creation of a perpetual motion machine,which would work in a similar way (i.e., a VD of the first kind).
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 equalization of temperatures between these objects, all thermal processes stop.
Planck's postulate
All of the above applies to electrical, magnetic, chemical phenomena, as well as processes occurring in outer space. Today, thermodynamic laws are of particular importance. Already, scientists are intensively working 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 universe.
The formulation of Planck's postulate is as follows:
The entropy of a properly formed crystal of a pure substance at absolute zero temperatures is zero.
This position was presented to the world by the author in 1911. And in those days caused a lot of controversy. However, 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's 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 just considered the starting point. It is proved that in such a state the energy of the molecules of any substance is zero. Their movement is completely stopped. In a crystal lattice, atoms occupy a clear, unchanging position in its nodes, without being able to fluctuate even slightly.
It goes without saying that all thermal phenomena in the system also stop under given conditions. Planck's postulate is about the state of a regular crystal at absolute temperature zero.
Measure of disorder
We can know the internal energy, volume and pressure of various substances. That is, we have every chance to describe the macrostate of this system. But this does not mean that it is possible to say something definite about the microstate of some 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. At the same time, under normal conditions, the molecules are in constant motion, constantly collide with each other and scatter in different directions, changing direction every fraction of a moment. And their behavior is dominated by chaos.
To determine the degree of disorder in physics, a special quantity called entropy has been introduced. It characterizes the degree of unpredictability of the system.
Entropy (S) is a thermodynamic state function that serves as a measuredisorder (disorder) of the system. The possibility of endothermic processes is due to a change in entropy, because in isolated systems the entropy of a spontaneous process increases ΔS >0 (the second law of thermodynamics).
Perfectly structured body
The degree of uncertainty is especially high in gases. As you know, they do not have a shape and volume. At the same time, they can expand indefinitely. Gas particles are the most mobile, therefore their speed and location is the most unpredictable.
Rigid bodies are quite another matter. In the crystal structure, each of the particles occupies a certain place, making only some vibrations from a certain point. Here it is not difficult, knowing the position of one atom, to determine the parameters of all the others. At absolute zero, the picture becomes completely obvious. This is what the third law of thermodynamics and Planck's postulate says.
If such a body is raised above the ground, the trajectory of movement of each of the molecules of the system will coincide with all the others, and besides, it will be in advance and easily determined. When the body, being released, falls down, the indicators will immediately change. From hitting the ground, the particles will acquire kinetic energy. It will give impetus to the thermal movement. This means that the temperature will increase, which will no longer be zero. And immediately entropy will arise, as a measure of the disorder of a chaotically functioning system.
Features
Any uncontrolled interaction provokes an increase in entropy. Under normal conditions, it can either remain constant or increase, but not decrease. In thermodynamics, this turns out to be a consequence of its second law, already mentioned earlier.
Standard molar entropies are sometimes called absolute entropies. They are not entropy changes 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 be determined. However, a consequence of this provision is also that in nature it is not possible to reach the temperature zero according to Kelvin, but only to get as close as possible to it.
Theoretically, Mikhail Lomonosov managed to predict the existence of a temperature minimum. He himself practically achieved the freezing of mercury to -65 ° Celsius. Nowadays, by means of laser cooling, the particles of substances have been brought almost to the state of absolute zero. More precisely, up to 10-9 degrees on the Kelvin scale. However, although this value is negligible, it is still not 0.
Meaning
The above postulate, formulated at the beginning of the last century by Planck, as well as subsequent works in this direction by the author, gave a huge impetus to the development of theoretical physics, resulting in a significant increase in itsprogress in many areas. And even a new science emerged - quantum mechanics.
Based on Planck's theory and Bohr's postulates, after some time, more precisely in 1916, Albert Einstein was able to describe the microscopic processes that occur when atoms move 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 Planck
This scientist was born in 1858 in April. Planck was born in the German city of Kiel in a family of famous military men, scientists, lawyers and church leaders. Even in the gymnasium, he showed remarkable abilities in mathematics and other sciences. In addition to exact disciplines, he studied music, where he also showed his considerable talents.
When he entered the university, he chose to study theoretical physics. Then he worked in Munich. Here he began to study thermodynamics, presenting his work to the scientific world. In 1887 Planck continued his activities in Berlin. This period includes such a brilliant scientific achievement as the quantum hypothesis, the deep meaning of which people were able to understand only 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.
