For several centuries, physicists have suggested that temperature is determined by the presence of an invisible and weightless substance in a gas in gases. Many theories have been put forward explaining its movement within matter and between different objects. Only M.V. Lomonosov was able to explain the real nature of matter by creating a molecular-kinetic theory of gases. In his arguments and calculations, he was able to prove that there is no calorific in nature. The temperature depends on the speed of the chaotic motion of the molecules. He introduced the concept of internal energy, and also explained how it changes in a real process.
What arguments did M.V. Lomonosov to prove the molecular-kinetic theory of gases
Having first speculated that no calorific exists in nature, he met powerful resistance from venerable scientists of that period. They all acknowledged the presence of the calorific, but the novice researcher did not. Then at one of the meetings with German and English physicists the following was said: “Dear teachers. Where did the calorie come from in the cow? She ate cold grass, and then her body warmed up due to the fact that a change in internal energy had occurred in her insides. Where did it come from? And the origin of heat in the body is explained by the fact that the grass has chemical energy, which the animal’s body has converted into this heat. So, we are observing the phenomenon of the transition of energy from one state to another. ” They listened to him, asked dozens of questions. Following the discussion, the law of energy change was also formulated (it is also called the law of conservation of energy), which was recognized by all those present. Later, a small collection of hypotheses was published, which was the first publication in which the molecular-kinetic theory of gases was recognized.
What did the theory of MV give to the researchers? Lomonosov
It seems today that everything is logical in thermodynamics. But it should be remembered that more than 250 years have passed from the first assumptions to the present day. French researcher J. Charles discovered the law of proportionality to pressure growth with increasing gas temperature. He then explained the change in the internal energy of the gas when heated. Derived my formula. Gay-Lussac, who investigated gas heating at constant pressure, continued his research after 20 years. He watched as the piston changes its position, placed inside the glass cylinder during heating and cooling. Here he came close to discovering the concept of gas constant. He did not take advantage of the research that Robert Boyle performed 140 years earlier. Only the works of Mariotte, completed later and formulated in the Boyle-Mariotte law, helped Benoit Paul Emile Clapeyron formulate the first concept of the equation of state of an ideal gas.
After 40 years, D.I. Mendeleev supplemented the equation of state with the results of his research. Now the law of Klaiperon-Mendeleev is the basis for thermodynamics around the world. It mathematically determines the change in internal energy from the temperature of the gas. The discoveries of the basic laws were confirmed by practice. Thermal machines were created that worked on the thermodynamic cycles of Otto, Diesel, Trinkler and other scientists.
Only at the beginning of the 20th century the experience of the predecessors was generalized and textbooks on molecular physics and technical thermodynamics were written, which harmoniously and logically expound the totality of discoveries.
A few words about the law of ideal gas state
pV = mRT
Today, when deriving any dependencies, the ideal gas equation of state is used. No one is embarrassed by the parameters included in it, which have well-defined concepts. Conclusions from the basic gas law give another important formula characterizing the change in internal energy:
dU = cvDT,
here dU is the differential of the change in internal energy, and cv is the heat capacity of the gas at a constant volume. As a result of discussions about the nature of the gas constant, R, it was established that it characterizes the work of gas at constant pressure.