The law of conservation of energy states that the amount of energy in any process remains unchanged. But he says nothing about what energy transformations are possible.

Z-energy conservation does not prohibit, processes that are experienced do not occur:

Heating a hotter body with a colder one;

Spontaneous swinging of the pendulum from a state of rest;

Collecting sand into stone, etc.

Processes in nature have a certain direction. They cannot flow spontaneously in the opposite direction. All processes in nature are irreversible(aging and death of organisms).

Irreversible a process can be called such a process, the reverse of which can occur only as one of the links of a more complex process. Spontaneous These are processes that occur without the influence of external bodies, and therefore without changes in these bodies).

Processes of transition of a system from one state to another, which can be carried out in the opposite direction through the same sequence of intermediate equilibrium states, are called reversible. In this case, the system itself and the surrounding bodies completely return to their original state.

Second zn thermodynamics indicates the direction of possible energy transformations and thereby expresses the irreversibility of processes in nature. It was established by direct generalization of experimental facts.

R. Clausius' formulation: it is impossible to transfer heat from a colder system to a hotter one in the absence of simultaneous changes in both systems or surrounding bodies.

W. Kelvin's formulation: it is impossible to carry out such a periodic process, the only result of which would be the production of work due to heat taken from one source.

Impossible thermal perpetual motion machine of the second kind, i.e. engine making mechanical work due to the cooling of any one body.

The explanation of the irreversibility of processes in nature has a statistical (probabilistic) interpretation.

Purely mechanical processes (without taking into account friction) are reversible, i.e. are invariant (do not change) when replacing t→ -t. The equations of motion of each individual molecule are also invariant with respect to time transformation, since contain only distance-dependent forces. This means that the reason for the irreversibility of processes in nature is that macroscopic bodies contain very a large number of particles.

The macroscopic state is characterized by several thermodynamic parameters (pressure, volume, temperature, etc.). The microscopic state is characterized by specifying the coordinates and velocities (moments) of all particles that make up the system. One macroscopic state can be realized huge number microstates.

Let us denote: N is the total number of states of the system, N 1 is the number of microstates that realize a given state, w is the probability of a given state.

The larger N1, the greater the probability of a given macrostate, i.e. the longer the system will remain in this state. The evolution of the system occurs in the direction from unlikely states to more probable ones. Because mechanical movement- this is an ordered movement, and thermal is chaotic, then mechanical energy turns into thermal. In heat exchange, a state in which one body has a higher temperature (molecules have a higher average kinetic energy), less likely than a state in which the temperatures are equal. Therefore, the heat exchange process occurs in the direction of equalizing temperatures.

Entropy - measure of disorder. S - entropy.

where k is Boltzmann's constant. This equation reveals the statistical meaning of the laws of thermodynamics. The amount of entropy in all irreversible processes increases. From this point of view, life is a constant struggle to reduce entropy. Entropy is related to information, because information leads to order (if you know a lot, you will soon grow old).

Reversible and irreversible processes, ways of changing the state of a thermodynamic system.

The process is called reversible, if it allows the system under consideration to return from the final state to the initial one through the same sequence of intermediate states as in the direct process, but passed in reverse order. In this case, not only the system, but also the environment returns to its original state. A reversible process is possible if it occurs in equilibrium both in the system and in the environment. It is assumed that equilibrium exists between the individual parts of the system under consideration and at the border with environment. A reversible process is an idealized case, achievable only with an infinitely slow change in thermodynamic parameters. The rate at which equilibrium is established must be greater than the rate of the process under consideration.

If it is impossible to find a way to return both the system and the bodies in the environment to their original state, the process of changing the state of the system is called irreversible.

Irreversible processes can occur spontaneously in only one direction; These are diffusion, thermal conductivity, viscous flow and more. For chemical reaction apply the concepts of thermodynamic and kinetic reversibility, which coincide only in close proximity to the equilibrium state. In practice, systems are often found that are in partial equilibrium, i.e. in equilibrium with respect to certain types of processes, while the system as a whole is nonequilibrium. For example, a sample of hardened steel has spatial heterogeneity and is a system that is nonequilibrium with respect to diffusion processes; however, equilibrium cycles of mechanical deformation can occur in this sample, since the relaxation times of diffusion and deformation in solids differ by tens of orders of magnitude. Consequently, processes with a relatively long relaxation time are kinetically inhibited and can not be taken into account when thermodynamically. analysis of faster processes.

General conclusion about the irreversibility of processes in nature. The transfer of heat from a hot body to a cold one mechanical energy to the internal - these are examples of the most typical irreversible processes. The number of such examples can be increased almost unlimitedly. They all say that processes in nature have a certain direction, which is not reflected in the first law of thermodynamics. All macroscopic processes in nature proceed only in one specific direction. They cannot flow spontaneously in the opposite direction. All processes in nature are irreversible, and the most tragic of them are the aging and death of organisms.
The importance of this law is that from it one can draw a conclusion about the irreversibility of not only the heat transfer process, but also other processes in nature. If heat in some cases could be spontaneously transferred from cold bodies to hot ones, then this would make it possible to make other processes reversible. All processes spontaneously proceed in one specific direction. They are irreversible. Heat always moves from a hot body to a cold one, and the mechanical energy of macroscopic bodies - into internal energy.
The direction of processes in nature is indicated by the second law of thermodynamics.

1. 1. Irreversibility of processes in nature Completed by: student of class 10 “B” Andronova Anna
2. 2. Irreversible is a process that cannot be carried out in the opposite direction through all the same intermediate states.
3. 3. The law of conservation of energy does not prohibit processes that do not occur experimentally: - heating a hotter body with a colder one; - spontaneous swinging of a pendulum from a state of rest; - collecting sand into a stone, etc. Processes in nature have a certain direction. They cannot flow spontaneously in the opposite direction. All processes in nature are irreversible.
4. 4. Examples of irreversible processes During diffusion, equalization of concentrations occurs spontaneously. The reverse process by itself will never occur: a mixture of gases, for example, will never spontaneously separate into its constituent components. Thermal conductivity The process of converting mechanical energy into internal energy during inelastic impact or friction is also irreversible.
5. 5. Let us give another example: Oscillations of a pendulum removed from an equilibrium position. Due to the work of friction forces, the mechanical energy of the pendulum decreases, and the temperature of the pendulum and the surrounding air (and therefore their internal energy) slightly increases. The reverse process is also energetically acceptable, when the amplitude of the pendulum’s oscillations increases due to the cooling of the pendulum itself and the environment. But such a process is never observed. Mechanical energy spontaneously transforms into internal energy, but not vice versa. In this case, the energy of the ordered motion of the body as a whole is converted into the energy of disordered thermal motion of the molecules composing it.
6. 6. “The Arrow of Time” and the problem of irreversibility in natural science One of the main problems in classical physics for a long time remained the problem of the irreversibility of real processes in nature. Almost all real processes in nature are irreversible: this is the damping of a pendulum, the evolution of a star, and human life. The irreversibility of processes in nature, as it were, sets the direction on the time axis from the past to the future. The English physicist and astronomer A. Eddington figuratively called this property of time “the arrow of time.”
7. 7. The second law of thermodynamics indicates the direction of possible energy transformations and thereby expresses the irreversibility of processes in nature. It was established by direct generalization of experimental facts.
8. 8.  R. Clausius’s formulation: it is impossible to transfer heat from a colder system to a hotter one in the absence of simultaneous changes in both systems or surrounding bodies. W. Kelvin’s formulation: it is impossible to carry out such a periodic process, the only result of which would be the production of work due to heat taken from one source.
9. 9. Clausius Rudolf (1822 -1888) Clausius contributed fundamental work in the field of molecular kinetic theory of heat. Clausius's work contributed to the introduction statistical methods into physics. Clausius made an important contribution to the theory of electrolysis. He theoretically substantiated the Joule-Lenz law, developed the theory of polarization of dielectrics, on the basis of which he established the relationship between dielectric constant and polarizability.
10. 10. W. Kelvin (1824-1907) William Kelvin is the author of many theoretical works in physics, he studied the phenomena electric current, dynamic geology. Together with James Joule, Kelvin conducted experiments on the cooling of gases and formulated the theory of real gases. The absolute thermodynamic temperature scale received his name.
11. 11. The problem of irreversibility of processes in nature Essentially, all processes in macrosystems are irreversible. A fundamental question arises: what is the reason for irreversibility? This looks especially strange when you consider that all the laws of mechanics are time reversible. And yet, no one has seen, for example, a broken vase spontaneously recover from the fragments. This process can be observed if, having first filmed it, view it in the opposite direction, but not in reality. The prohibitions established by the second law of thermodynamics also become mysterious The solution to this complex problem came with the discovery of a new thermodynamic quantity - entropy - and the disclosure of its physical meaning.
12. 12. Entropy is a measure of the disorder of a system consisting of many elements. In particular, in statistical physics, it is a measure of the probability of the occurrence of any macroscopic state.
13. 13. The reality of irreversible processes Many frequently observed processes are irreversible: try to throw a stone into water - you will always see concentric circles-waves diverging from the place where it hits the water and never converging to this place. In chemistry, examples of irreversible processes are reactions that always occur with an increase in entropy. In biology, life always begins with birth, continues with youth, maturity and old age and ends with death, and not only the reverse development of living organisms never occurs, but even this process never stops. In astronomy, these are stars that are gradually fading or subject to gravitational collapse.
14. 14. Thank you for your attention!

The law of conservation of energy states that the amount of energy during any transformation remains unchanged. But he says nothing about what energy transformations are possible. Meanwhile, many processes that are completely acceptable from the point of view of the law of conservation of energy never occur in reality.

Examples of irreversible processes. Heated bodies gradually cool down, transferring their energy to colder surrounding bodies. The reverse process of heat transfer from cold

body to hot does not contradict the law of conservation of energy, but such a process has never been observed.

Another example. The oscillations of the pendulum, removed from the equilibrium position, die out (Fig. 49; 1, 2, 3, 4 - successive positions of the pendulum at maximum deviations from the equilibrium position). Due to the work of friction forces, mechanical energy decreases, and the temperature of the pendulum and the surrounding air (and therefore their internal energy) slightly increases. The reverse process is also energetically permissible, when the amplitude of the pendulum’s oscillations increases due to the cooling of the pendulum itself and the environment. But such a process has never been observed. Mechanical energy spontaneously transforms into internal energy, but not vice versa. In this case, the ordered movement of the body as a whole turns into disordered thermal movement of the molecules composing it.

General conclusion about the irreversibility of processes in nature. The transition of heat from a hot body to a cold one and mechanical energy into internal energy are examples of the most typical irreversible processes. The number of such examples can be increased almost unlimitedly. They all say that processes in nature have a certain direction, which is not reflected in any way in the first law of thermodynamics. All macroscopic processes in nature proceed only in one specific direction. They cannot flow spontaneously in the opposite direction. All processes in nature are irreversible, and the most tragic of them are the aging and death of organisms.

A precise formulation of the concept of an irreversible process. To properly understand the essence of irreversibility of processes, it is necessary to make the following clarification. Irreversible is a process whose reverse can occur only as one of the links in a more complex process. So, you can again increase the swing of the pendulum by pushing it with your hand. But this increase does not occur by itself, but becomes possible as a result of a more complex process involving the movement of the hand.

It is possible, in principle, to transfer heat from a cold body to a hot one. But this requires a refrigeration unit that consumes energy.

Cinema is the opposite. A striking illustration of the irreversibility of phenomena in nature is watching a movie in reverse. For example, a jump into water will look like this. The calm water in the pool begins to boil, legs appear, rapidly moving upward, and then

and the whole diver. The surface of the water quickly calms down. Gradually, the diver’s speed decreases, and now he is calmly standing on the tower. What we see on the screen could happen in reality if the processes could be reversed. The “absurdity” of what is happening stems from the fact that we are accustomed to a certain direction of processes and do not doubt the impossibility of their reverse flow. But such a process as lifting a diver onto a tower from the water does not contradict either the law of conservation of energy, or the laws of mechanics, or any laws at all, except for the second law of thermodynamics.

Second law of thermodynamics. The second law of thermodynamics indicates the direction of possible energy transformations and thereby expresses the irreversibility of processes in nature. It was established by direct generalization of experimental facts.

There are several formulations of the second law, which, despite their external differences, essentially express the same thing and are therefore equivalent.

The German scientist R. Clausius formulated this law as follows: it is impossible to transfer heat from a colder system to a hotter one in the absence of other simultaneous changes in both systems or in surrounding bodies.

Here the experimental fact of a certain direction of heat transfer is stated: heat always passes by itself from hot bodies to cold ones. True, in refrigeration units heat transfer occurs from a cold body to a warmer one, but this transfer is associated with “other changes in the surrounding bodies”: cooling is achieved through work.

The importance of this law lies in the fact that from it one can draw a conclusion about the irreversibility of not only the heat transfer process, but also other processes in nature. If heat in some cases could be spontaneously transferred from cold bodies to hot ones, then this would make it possible to make other processes reversible. In particular, it would make it possible to create engines that completely convert internal energy into mechanical energy.

Entropy. Physical meaning entropy. Entropy for reversible and irreversible processes in a closed system. Second beginning thermodynamics and the conversion of heat into work.

The harmony of the processes of conservation, destruction and creation is the basis of the existence and evolution of the Universe. Synergetics recognized the Universe as open, but did not find God in it! Before the advent of synergetics, the world was dominated by the second law of thermodynamics. In accordance with this law, the evolution of the Universe was accompanied by an increase in entropy and the equalization of all gradients and potentials. The world was heading toward a state of homogeneous chaos, which was called “heat death.” Synergetics - the science of self-organization and cooperation in natural phenomena. It is synergetic processes that underlie morphogenesis - the emergence of new forms of matter. At the same time, the authors believed that the prerequisites for such processes are exchange with the environment, the random nature of external or internal influences, as well as instability, nonlinearity and irreversibility. A process occurring in a system under the influence of certain factors should be considered reversible (irreversible) if when the influence of these factors ceases, the process stops and the system returns (does not return) to its original state

There are several formulations of the second law of thermodynamics. One of them says that it is impossible to have a heat engine that would do work only due to a heat source, i.e. no refrigerator. The world's oceans could serve for him as a practically inexhaustible source of internal energy (Wilhelm Friedrich Ostwald, 1901). Other formulations of the second law of thermodynamics are equivalent to this one. Clausius' formulation (1850): a process in which heat would spontaneously transfer from less heated bodies to more heated bodies is impossible. There are several formulations of the second law of thermodynamics. One of them says that it is impossible to have a heat engine that would do work only due to a heat source, i.e. no refrigerator. The world's oceans could serve for him as a practically inexhaustible source of internal energy (Wilhelm Friedrich Ostwald, 1901). Other formulations of the second law of thermodynamics are equivalent to this one. Clausius' formulation (1850): a process in which heat would spontaneously transfer from less heated bodies to more heated bodies is impossible.

Internal energy reserves in earth's crust and oceans can be considered practically unlimited. But having energy reserves is not enough. It is necessary to be able to use energy to set in motion machine tools in factories and factories, vehicles, tractors and other machines, to rotate the rotors of electric current generators, etc. Humanity needs device engines that can do work. Most of the engines on Earth are heat engines, i.e. devices that convert the internal energy of fuel into mechanical energy.

A heat engine (machine) is a device that performs mechanical work cyclically due to the energy supplied to it during heat transfer. The source of the incoming amount of heat in real engines can be burning organic fuel, a boiler heated by the Sun, a nuclear reactor, geothermal water, etc. A heat engine (machine) is a device that performs mechanical work cyclically due to the energy supplied to it during heat transfer. The source of the incoming amount of heat in real engines can be burning organic fuel, a boiler heated by the Sun, a nuclear reactor, geothermal water, etc.

Currently, two types of engines are most common: a piston internal combustion engine (land and water transport) and a steam or gas turbine (energy). Modern thermal engines include rocket and aircraft engines.

IN theoretical model In a heat engine, three bodies are considered: a heater, a working fluid and a refrigerator. Heater – a thermal reservoir (large body), the temperature of which is constant. In each cycle of engine operation, the working fluid receives a certain amount of heat from the heater, expands and performs mechanical work. The transfer of part of the energy received from the heater to the refrigerator is necessary to return the working fluid to its original state. In the theoretical model of a heat engine, three bodies are considered: a heater, a working fluid and a refrigerator. Heater – a thermal reservoir (large body), the temperature of which is constant. In each cycle of engine operation, the working fluid receives a certain amount of heat from the heater, expands and performs mechanical work. The transfer of part of the energy received from the heater to the refrigerator is necessary to return the working fluid to its original state.

For each cycle, based on the first law of thermodynamics, we can write that the amount of heat Qheat received from the heater, the amount of heat |Qcol| given to the refrigerator, and the work A performed by the working fluid are interconnected by the relation: A = Qheat – |Qcol |. In real technical devices, which are called heat engines, the working fluid is heated by the heat released during the combustion of fuel.

Efficiency of a heat engine If a model of the working fluid in a heat engine is given (for example, an ideal gas), then it is possible to calculate the change in the thermodynamic parameters of the working fluid during expansion and compression. This allows you to calculate Thermal efficiency engine based on the laws of thermodynamics. The figure shows cycles for which the efficiency can be calculated if the working fluid is an ideal gas and the parameters are specified at the transition points of one thermodynamic process to another.

Environmental consequences of the operation of thermal engines Intensive use of thermal engines in transport and in the energy sector (thermal and nuclear power plants) significantly affects the Earth's biosphere. Although there are scientific disputes about the mechanisms of influence of human activity on the Earth's climate, many scientists note the factors due to which such an influence can occur: 1. The greenhouse effect - an increase in the concentration of carbon dioxide (a product of combustion in heaters of heat engines) in the atmosphere. Carbon dioxide transmits visible and ultraviolet radiation from the Sun, but absorbs infrared radiation going into space from the Earth. This leads to an increase in the temperature of the lower layers of the atmosphere, increased hurricane winds and global melting of ice. 2.Direct influence of toxic exhaust gases on wildlife(carcinogens, smog, acid rain from combustion byproducts). 3. Destruction of the ozone layer during airplane flights and rocket launches. Ozone in the upper atmosphere protects all life on Earth from excess ultraviolet radiation Sun. The intensive use of heat engines in transport and energy (thermal and nuclear power plants) significantly affects the Earth's biosphere. Although there are scientific disputes about the mechanisms of influence of human activity on the Earth's climate, many scientists note the factors due to which such an influence can occur: 1. The greenhouse effect - an increase in the concentration of carbon dioxide (a product of combustion in heaters of heat engines) in the atmosphere. Carbon dioxide allows visible and ultraviolet radiation from the Sun to pass through, but absorbs infrared radiation from the Earth into space. This leads to an increase in the temperature of the lower layers of the atmosphere, increased hurricane winds and global melting of ice. 2. Direct impact of toxic exhaust gases on wildlife (carcinogens, smog, acid rain from combustion by-products). 3. Destruction of the ozone layer during airplane flights and rocket launches. Ozone in the upper atmosphere protects all life on Earth from excess ultraviolet radiation from the Sun.