Change in entropy
Entropy is a concept that has been introducedin thermodynamics. With the help of this quantity, the measure of energy dissipation is determined. Any system experiences a confrontation that arises between heat and a force field. Increasing the temperature leads to a decrease in the degree of order. To determine the measure of disorder and introduced a quantity, called entropy. It characterizes the degree of exchange of energy flows in both closed and open systems.
The change in entropy in isolated schemesoccurs in the direction of increase together with the growth of heat. This measure of disorder reaches its maximum value in a state characterized by thermodynamic equilibrium, which is most chaotic.
If the system is open and at the same timethe equilibrium entropy changes in the direction of decrease. The magnitude of this measure in this version is characterized by the formula. To obtain it, the two values are summed:
- the flow of entropy, which occurs due to the exchange of heat and substances with the external environment;
- the magnitude of the change in the indicator of chaotic motion within the system.
The change in entropy occurs in any medium, wherethere are biological, chemical and physical processes. This phenomenon is realized with a certain speed. The change in entropy can be a positive value - in this case, the inflow of this indicator into the system from the external environment occurs. There are cases when a value indicating a change in entropy is defined with a minus sign. Such a numerical value indicates an outflow of entropy. The system can be in a stationary state. In this case, the amount of entropy produced is offset by the outflow of this indicator. An example of such a situation is the state of a living organism. It is nonequilibrium, but at the same time stationary. Any organism pumps entropy, which has a negative value, from its environment. The isolation of the measure of disorder from it can even exceed the amount of income.
The production of entropy occurs in any complexsystems. In the process of evolution, information is exchanged between them. For example, when water evaporates, information about the spatial arrangement of its molecules is lost. There is a process of increasing entropy. If the liquid freezes, then the uncertainty of the arrangement of the molecules decreases. In this case, the entropy decreases. Cooling the liquid causes a decrease in its internal energy. However, when the temperature reaches a certain value, despite the removal of heat from the water, the temperature of the substance remains unchanged. This means that the transition to crystallization begins. The change in entropy in an isothermal process of this type is accompanied by a decrease in the measure of the randomness of the system.
A practical method for measuringtemperature and heat of melting of the substance, is the carrying out of works, the result of which is the construction of a solidification diagram. In other words, on the basis of the data obtained as a result of the study, it is possible to draw a curve that indicates the temperature dependence of the substance versus time. In this case, the external conditions must be unchanged. Determine the change in entropy is possible by processing the graphic data of the results of the experiment. On such curves there is always a section on which the line has a horizontal gap. The temperature corresponding to this segment is the solidification temperature.
Change of any substance, accompanied bytransition from a solid body to a liquid at a temperature of its environment equal to the melting point, and vice versa, is referred to a phase change of the first kind. This changes the density of the system, its internal energy and entropy.
