The first law of thermodynamics
The first law of thermodynamics states thatchange of internal energy is possible only in the presence of external influences. In other words, if a certain amount of heat is communicated to the system and work is performed on it, then the activity of this body will increase.
The first law of thermodynamics, the definition of whichis a law of conservation of energy, applies only to systems that have macroscopic dimensions. It is the mathematical expression of the first principle of science, which studies the general properties of systems. This is thermodynamics.
The state of the system can be changed with the help oftwo completely different ways. The first of these is related to the action of moving surrounding bodies to distances that are defined as macroscopic. It is also possible to work in the immediate vicinity of objects above the system. The second method involves the transfer or removal of heat energy. In this case, the surrounding body system does not change its location.
The first law of thermodynamics states thatthe initial and final values of thermal energy and work serve as characteristics of the process that takes place over the substance under consideration. In the case when the system makes a closed cycle, returning to its original state, the magnitude of the temperature effect will be similar to the work that the body will produce.
The first law of thermodynamics allows us to makethe conclusion that there is a concept of internal energy. It is a characteristic of the state of the system. There are cases when the internal energy of an isolated body remains unchanged. In this case, heat exchange occurs only between substances inside the system. Then that magnitude of heat that flows away from the cooling bodies is equal to its amount flowing to the bodies heated. The total internal energy of a closed system is thus unchanged. This state represents the heat balance.
If a certain amount of energy is transferred to the system, then the internal activity of the body is taken as a positive value, and in the reverse processes - as a negative value.
The first law of thermodynamics chemistry also appliesin their studies. It is believed that the internal energy is stored in the kinetic state. Its expression is the movement of ions, atoms and molecules. In addition, the energy of the system is stored in intranuclear forces and chemical bonds. The absolute value of the activity of a substance can not be determined. In this regard, it is established its change associated with a particular process.
The first law of thermodynamics in chemistry is consideredwork as an extension of the substance. Its action is directed against the external atmospheric pressure. The positive value of this work means that the system increases its internal energy. With a negative value, a loss occurs.
Work, as well as heat does not belong to the propertiessystem. These parameters serve to characterize the interaction of matter with its environment. The work thus serves as a quantitative expression for the transfer of the motion of molecules, which is ordered, and heat is the equivalent of chaotic displacement. This is especially pronounced in chemical reactions. If the process is not yet in its initial stage or already completed, it is impossible to assert that there are in the system of work and heat. During the chemical reaction, all the atoms are rearranged. In this case, some bonds are destroyed, and others are formed. As a result, the internal state of the system and its energy change. These transformations cause the outflow of heat from the substance into its environment.
According to the first law of thermodynamics, workany mechanism is provided by a certain amount of heat, which must be received from the outside, or by reducing its internal energy. Thus, the efforts of many inventors, trying to construct a perpetual motion machine, were initially doomed to failure.
