Change in entropy

Entropy is a concept that was introduced in thermodynamics. With the help of this quantity, a measure of the 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 value, called entropy. It characterizes the degree of exchange of energy flows in both closed and open systems.

The change in entropy under isolated schemes occurs in the direction of increase along with the increase in 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 nonequilibrium at the same time, then the entropy change occurs in the direction of decrease. The magnitude of this measure in this version is characterized by the formula. To obtain it, the two quantities 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 environment where biological, chemical and physical processes occur. 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 complex systems. 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 that makes it possible to measure the temperature and heat of melting of a substance is to carry out works whose result 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 image 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 curing temperature.

The change in any substance, accompanied by a transition from a solid to a liquid at a temperature of its environment equal to the melting point, and vice versa, is referred to as a first-order phase change. This changes the density of the system, its internal energy and entropy.