Absolute zero temperature and its physical meaning. Absolute zero

Absolute zero corresponds to a temperature of −273.15 °C.

It is believed that absolute zero is unattainable in practice. Its existence and position on the temperature scale follows from extrapolation of the observed physical phenomena, while such extrapolation shows that at absolute zero the energy of thermal motion of molecules and atoms of a substance should be equal to zero, that is, the chaotic movement of particles stops, and they form an ordered structure, occupying a clear position at the nodes of the crystal lattice. However, in fact, even at absolute zero temperature, the regular movements of the particles that make up matter will remain. The remaining oscillations, such as zero-point oscillations, are due to the quantum properties of the particles and the physical vacuum that surrounds them.

At present, in physical laboratories it has been possible to obtain temperatures exceeding absolute zero by only a few millionths of a degree; to achieve it itself, according to the laws of thermodynamics, is impossible.

Notes

Literature

G. Burmin. Assault on absolute zero. - M.: “Children’s Literature”, 1983.

Temperature, which expresses the absence of heat, is equal to 218° C. Dictionary of foreign words included in the Russian language. Pavlenkov F., 1907. absolute zero temperature (physical) - the lowest possible temperature (273.15°C). Big dictionary… … Dictionary of foreign words of the Russian language

absolute zero- The extremely low temperature at which the thermal movement of molecules stops; on the Kelvin scale, absolute zero (0°K) corresponds to –273.16±0.01°C... Dictionary of Geography

Noun, number of synonyms: 15 round zero (8) small man (32) small fry ... Synonym dictionary

The extremely low temperature at which the thermal movement of molecules stops. The pressure and volume of an ideal gas, according to Boyle-Mariotte’s law, becomes equal to zero, and the beginning of the absolute temperature on the Kelvin scale is taken to be... ... Ecological dictionary

absolute zero- - [A.S. Goldberg. English-Russian energy dictionary. 2006] Energy topics in general EN zeropoint ... Technical Translator's Guide

The beginning of the absolute temperature reference. Corresponds to 273.16° C. Currently, in physical laboratories it has been possible to obtain a temperature exceeding absolute zero by only a few millionths of a degree, and to achieve it, according to the laws... ... Collier's Encyclopedia

absolute zero- absoliutusis nulis statusas T sritis Standartizacija ir metrologija apibrėžtis Termodinaminės temperatūros atskaitos pradžia, esanti 273.16 K žemiau vandens trigubojo taško. Tai 273.16 °C, 459.69 °F arba 0 K temperatūra. atitikmenys: engl.… … Penkiakalbis aiškinamasis metrologijos terminų žodynas

absolute zero- absoliutusis nulis statusas T sritis chemija apibrėžtis Kelvino skalės nulis (−273.16 °C). atitikmenys: engl. absolute zero rus. absolute zero... Chemijos terminų aiškinamasis žodynas

14. Absolute temperature and its physical meaning
Equation of state of an ideal gas (Mendeleev-Clapeyron equation)

The term “temperature” refers to the degree of heating of the body.

There are several temperature scales. On the absolute (thermodynamic) scale, temperature is measured in kelvins (K). Zero on this scale is called the absolute zero of temperature, approximately equal to - 273 0 C. At absolute zero, the translational movement of molecules stops.

Thermodynamic temperature T is related to temperature on the Celsius scale by the following relationship:
T = (t 0 + 273)K
For an ideal gas, there is a proportional relationship between the absolute temperature of the gas and the average kinetic energy of the translational motion of the molecules:
,
where k is Boltzmann’s constant, k = 1.38 10 – 23 J/C

Thus, absolute temperature is a measure of the average kinetic energy of the translational motion of molecules. This is its physical meaning.

Substituting into the equation p = n expression for average kinetic energy
= kT, we get

p = n kT = nkT
From the basic MKT equation of an ideal gas p = nkT with the substitution
,
we can get the equation
, or A kT
N A k = R- universal gas constant, R = 8.31

The equation is called the ideal gas equation of state (Mendeleev-Clapeyron equation).
^ 15. Gas laws. Isoprocess graphs.

The isothermal process (T = const) obeys the Boyle–Mariotte law: for a given mass of gas at a constant temperature, the product of pressure and volume is a constant value.

, or or

The isobaric process (p = const) obeys the Gay-Lussac law: for a given mass of gas at constant pressure, the ratio of gas volume to absolute temperature is a constant value.

Or or

The isochoric process (V = const) obeys Charles’s law: for a given mass of gas at a constant volume, the ratio of gas pressure to absolute temperature is a constant value.

Or or

Internal energy of an ideal gas. Ways to change internal energy.

Quantity of heat. Work in thermodynamics

Internal energy is the sum of the kinetic energy of the chaotic movement of molecules and the potential energy of their interaction.

Since the molecules of an ideal gas do not interact with each other, the internal energy U of an ideal gas is equal to the sum of the kinetic energies of chaotically moving molecules:
, Where .
Thus,

,
Where .

For monatomic gas i = 3, for diatomic i = 5, for three (or more) atomic i = 6.

Change in internal energy of an ideal gas
.
The internal energy of an ideal gas is a function of its state. Internal energy can be changed in two ways:

by heat exchange;
by doing work.

The process of changing the internal energy of a system without performing mechanical work is called heat exchange or heat transfer. There are three types of heat transfer: conduction, convection and radiation.

^ The amount of heat is a quantity that is a quantitative measure of the change in the internal energy of a body during the process of heat transfer.

The amount of heat required for heating (or given off by the body during cooling) is determined by the formula:
where c is the specific heat capacity of the substance
Work in thermodynamics

Elementary work d A = p dV. At p = const
^ 16. System status. Process. First law (first law) of thermodynamics
System of bodies called the set of bodies under consideration. An example of a system would be a liquid and vapor in equilibrium with it. In particular, the system can consist of one body.

Any system can be in different states, differing in temperature, pressure, volume, etc. The quantities characterizing the state of the system are called state parameters.

Not always any system parameter has a certain value. If, for example, the temperature at different points of the body is not the same, then a certain temperature value cannot be assigned to the body. In this case, the state of the system is called nonequilibrium.

Equilibrium The state of a system is a state in which all the parameters of the system have certain values that remain constant under constant external conditions for an arbitrarily long time.

Process call the transition of a system from one state to another.

Internal energy is a function of the state of the system. This means that whenever a system finds itself in a given state, its internal energy takes on the value inherent in this state, regardless of the previous history of the system. The change in the internal energy of a system during its transition from one state to another (regardless of the path along which the transition occurs) is equal to the difference in the values of the internal energy in these states.

According to the first law of thermodynamics the amount of heat imparted to the system goes to increase the internal energy of the system and to perform work on external bodies.

Application of the first law of thermodynamics to processes in gases. Adiabatic process.

Isothermal process (T=const)

Because .
Gas work in an isothermal process
.

Isochoric process (V=const)

Since Therefore

Isobaric process (p=const)

Adiabatic process (Q = 0).

Adiabatic is a process that occurs without heat exchange with environment.

The adiabatic equation (Poisson equation) has the form .

According to the first law of thermodynamics Hence, .

During adiabatic expansion, therefore (the gas cools).

During adiabatic compression, therefore (the gas heats up). Adiabatic air compression is used to ignite fuel in diesel internal combustion engines.
^ 17. Heat engines
A heat engine is a device that converts the energy of burned fuel into mechanical energy. A heat engine in which the working parts periodically return to their original position is called a periodic heat engine.

Heat engines include:

steam engines,
internal combustion engines (ICE),
jet engines,
steam and gas turbines,
refrigeration machines.

For the operation of a periodic heat engine, the following conditions must be met:

the presence of a working fluid (steam or gas), which, heating up during fuel combustion and expanding, is capable of mechanical work;
use of a circular process (cycle);
the presence of a heater and refrigerator.

Second law of thermodynamics

The heat engine circuit has the form shown in the figure. the amount of heat received by the working fluid from the heater is the amount of heat given by the working fluid to the refrigerator.

It is clear from the diagram that a heat engine does work only by transferring heat in one direction, namely from more heated bodies to less heated ones, and all the heat taken from the heater cannot be

Converted into mechanical work. This is not an accident, but the result of objective laws existing in nature, which are reflected in the second law of thermodynamics. The second law of thermodynamics shows in which direction thermodynamic processes can proceed, and has several equivalent formulations. Specifically, Kelvin's formulation is: such a periodic process is impossible, the only result of which is the conversion of the heat received from the heater into work equivalent to it.

^ Heat engine efficiency. Carnot cycle.

The coefficient of performance (efficiency) of a heat engine is a value equal to the ratio of the amount of heat converted by the engine into mechanical work to the amount of heat received from the heater:

^ The efficiency of a heat engine is always less than unity.

To determine the maximum possible efficiency value of a heat engine, the French engineer S. Carnot calculated an ideal reversible cycle consisting of two isotherms and two adiabats. He proved that the maximum efficiency value of an ideal heat engine operating without losses on a reversible cycle
.
Any real heat engine operating with a heater at temperature and a refrigerator at temperature cannot have an efficiency that exceeds the efficiency of an ideal heat engine at the same temperatures.
ELECTROMAGNETISM
^ 1. Electrification of bodies. Law of conservation of electric charge. Coulomb's law
Many particles and bodies are capable of interacting with each other with forces that, like gravitational forces, are proportional to the square of the distance between them, but are many times greater than gravitational forces. This type of particle interaction is called electromagnetic.

^ Consequently, electric charge is a quantitative measure of the ability of particles to electromagnetic interactions.

There are two types of electric charge, conventionally called positive and negative. Like charges repel, and unlike charges attract.

It has been experimentally established that the charge of any body consists of an integer elementary charges, i.e. electric charge is discrete. The elementary charge is usually denoted by the letter e. The charge of all elementary particles (if it is not zero) is the same in absolute value.
|e| = 1.6·10 –19 C
Any charge greater than an elementary one consists of an integer number of elementary charges
q = ± Ne (N = 1, 2, 3, …)
The electrification of bodies always comes down to the redistribution of electrons. If a body has an excess of electrons, then it is negatively charged; if it has a deficiency of electrons, then the body is positively charged.

^ In an isolated system, the algebraic sum of electric charges remains constant (law of conservation of electric charge):
q 1 + q 2 +…+ q N = ∑q i = const
The law governing the interaction force between point immobile charges was established by Coulomb (1785)

A point charge is a charged body, the dimensions of which can be neglected in comparison with the distances from this body to other bodies carrying an electric charge.

According to Coulomb's law, the force of interaction between two stationary point charges in a vacuum is directly proportional to the product of the charge moduli and inversely proportional to the square of the distance between them.

k – proportionality coefficient.

In SI k =	1
	4πε 0

k = 9 10 9 N m 2 / C 2 ε 0 = 8.85 10 -12 C 2 / N m 2 (ε 0 – electrical constant).

^ 2. Electric field. Tension electric field. The principle of superposition of electric fields
An electric field is a type of matter through which the interaction of electric charges occurs.

The strength characteristic of the electric field is the electric field strength.

The electric field strength at a given point is equal to the ratio of the force with which the field acts on a test charge placed at a given point in the field to the magnitude of this charge.
.
Electric field strength is measured in or in.

Field strength of a point charge.

According to the principle of superposition (superposition) of fields, the field strength of a system of charges is equal to the vector sum of the field strengths that would be created by each of the charges of the system separately.

+ q 1 - q 2

Electric fields can be represented graphically using electric field lines.

The electric field intensity line is a line whose tangent at each point coincides with the direction of the intensity vector at that point.

^ 3. Work of electrostatic field forces. Electrostatic field potential

F
dr α dl
1 q ´ 2

r 1 r 2

The force acting on a point charge located in the field of another charge is central. The central field of forces is potential. If the field is potential, then the work done to move a charge in this field does not depend on the path along which the charge movesa depends on the initial and final position of the charge And .

Work on the elementary path

= .
From this formula it follows that the forces acting on a charge in the field of a stationary charge are conservative, because the work done to move the charge is really determined by the initial and final positions of the charge.

From the course of mechanics it is known that the work of conservative forces on a closed path is equal to zero.

^ The circulation of the electrostatic field strength vector along any closed circuit is zero.

Potential

A body located in a potential field of forces has energy, due to which work is done by the field forces
.
Consequently, the potential energy of a charge in the field of a stationary charge
.
The value equal to the ratio of the potential energy of a charge to the magnitude of this charge is called the electrostatic field potential
.
Potential is an energy characteristic of an electric field.

Electric field potential of a point charge
.
The field potential created by a system of charged bodies is equal to the algebraic sum of the potentials created by each charge separately
.
A charge located at a field point with potential has energy
.
Work of field forces on a charge

The quantity is called voltage. Potential and potential difference (voltage) are measured in volts (V).
^ 4. Relationship between electrostatic field strength and potential
Work done by electric field forces on a charge along a segment of path
.

On the other hand, therefore.

It follows that
. ; ; .

.
The quantity in parentheses is called the potential gradient.

Consequently, the electric field strength is equal to the potential gradient taken with the opposite sign.

For a uniform electrostatic field, at the same time. Hence, , .

To visually depict the electric field, along with tension lines, surfaces of equal potential (equipotential surfaces) are used. The electrostatic field strength lines are perpendicular (orthogonal) to the equipotential surfaces.
^ 5. Conductors in an electrostatic field. The phenomenon of electrostatic induction. Dielectrics in an electrostatic field
Conductors in an electrostatic field. Electrostatic induction.

Conductors include substances that have free charged particles that can move in an orderly manner throughout the entire volume of the body under the influence of an electric field. The charges of such particles are called free.

Metals are conductors, some chemical compounds, aqueous solutions of salts, acids and alkalis, molten salts, ionized gases.

Let us consider the behavior of solid metal conductors in an electric field. In metals, free charge carriers are free electrons called conduction electrons.

+σ E 0 -σ
- +

If you introduce an uncharged metal conductor into a uniform electric field, then under the influence of the field in the conductor there appears a directed movement of free electrons in the direction opposite direction tension vector E O this field. Electrons will accumulate on one side of the conductor, forming an excess negative charge there, and their shortage on the other side of the conductor will lead to the formation of an excess positive charge there, i.e. There will be a separation of charges in the conductor. These uncompensated opposite charges appear on the conductor only under the influence of an external electric field, i.e. such charges are induced (induced), and in general the conductor still remains uncharged.

This type of electrification, in which, under the influence of an external electric field, a redistribution of charges occurs between parts of a given body is called electrostatic induction.

Appeared as a result of electrostatic induction on opposite parts of the conductor, uncompensated electric charges create their own electric field, its intensity E With inside the conductor is directed against the tension E O external field in which the conductor is placed. As the charges in the conductor separate and accumulate on opposite parts of the conductor, the voltage E With internal field increases and becomes equal E O. This leads to tension E the resulting field inside the conductor becomes zero. In this case, an equilibrium of charges occurs on the conductor.

The entire uncompensated charge in this case is located only on the outer surface of the conductor, and there is no electric field inside the conductor.

This phenomenon is used to create electrostatic protection, the essence of which is that to protect sensitive devices from the influence of electric fields, they are placed in metal grounded cases or grids.

^ Dielectrics in an electrostatic field.

Dielectrics include substances in which, under normal conditions (i.e., not too high temperatures and the absence of strong electric fields), there are no free electric charges.

Unlike conductors in dielectrics, charged particles are not able to move throughout the entire volume of the body, but can only move small distances (on the order of atomic ones) relative to their constant positions. Consequently, electric charges in dielectrics are related.

Depending on the structure of the molecules, all dielectrics can be divided into three groups. The first group includes dielectrics whose molecules have an asymmetric structure (water, alcohols, nitrobenzene). For such molecules, the centers of distribution of positive and negative charges do not coincide. Such molecules can be considered as electric dipoles.

Molecules that are electric dipoles are called polar. They have an electrical moment p = q l even in the absence of an external field.

The second group includes dielectrics whose molecules are symmetrical (for example, paraffin,

The limiting temperature at which the volume of an ideal gas becomes equal to zero is taken as absolute zero temperature.

Let's find the value of absolute zero on the Celsius scale.
Equating volume V in formula (3.1) zero and taking into account that

Hence the absolute zero temperature is

t= –273 °C. 2

This is the extreme, lowest temperature in nature, that “greatest or last degree of cold”, the existence of which Lomonosov predicted.

The highest temperatures on Earth - hundreds of millions of degrees - were obtained during explosions thermonuclear bombs. Even higher temperatures are typical for the inner regions of some stars.

2More accurate value of absolute zero: –273.15 °C.

Kelvin scale

The English scientist W. Kelvin introduced absolute scale temperatures Zero temperature on the Kelvin scale corresponds to absolute zero, and the unit of temperature on this scale is equal to a degree on the Celsius scale, so absolute temperature T is related to temperature on the Celsius scale by the formula

T = t + 273. (3.2)

In Fig. 3.2 shows the absolute scale and the Celsius scale for comparison.

The SI unit of absolute temperature is called kelvin(abbreviated as K). Therefore, one degree on the Celsius scale is equal to one degree on the Kelvin scale:

Thus, absolute temperature, according to the definition given by formula (3.2), is a derived quantity that depends on the Celsius temperature and on the experimentally determined value of a.

Reader: What physical meaning does absolute temperature have?

Let us write expression (3.1) in the form

Considering that temperature on the Kelvin scale is related to temperature on the Celsius scale by the relation T = t + 273, we get

Where T 0 = 273 K, or

Since this relation is valid for arbitrary temperature T, then Gay-Lussac’s law can be formulated as follows:

For a given mass of gas at p = const the following relation holds:

Task 3.1. At a temperature T 1 = 300 K gas volume V 1 = 5.0 l. Determine the volume of gas at the same pressure and temperature T= 400 K.

STOP! Decide for yourself: A1, B6, C2.

Problem 3.2. During isobaric heating, the volume of air increased by 1%. By what percentage did the absolute temperature increase?

= 0,01.

Answer: 1 %.

Let's remember the resulting formula

STOP! Decide for yourself: A2, A3, B1, B5.

Charles's Law

The French scientist Charles experimentally established that if a gas is heated so that its volume remains constant, the pressure of the gas will increase. The dependence of pressure on temperature has the form:

R(t) = p 0 (1 + b t), (3.6)

Where R(t) – pressure at temperature t°C; R 0 – pressure at 0 °C; b is the temperature coefficient of pressure, which is the same for all gases: 1/K.

Reader: Surprisingly, the temperature coefficient of pressure b is exactly equal to the temperature coefficient of volumetric expansion a!

Let us take a certain mass of gas with a volume V 0 at temperature T 0 and pressure R 0 . For the first time, maintaining the gas pressure constant, we heat it to a temperature T 1 . Then the gas will have a volume V 1 = V 0 (1 + a t) and pressure R 0 .

The second time, maintaining the volume of gas constant, we heat it to the same temperature T 1 . Then the gas will have pressure R 1 = R 0 (1 + b t) and volume V 0 .

Since in both cases the gas temperature is the same, the Boyle–Mariotte law is valid:

p 0 V 1 = p 1 V 0 Þ R 0 V 0 (1 + a t) = R 0 (1 + b t)V 0 Þ

Þ 1 + a t = 1 + b tÞ a = b.

So it's not surprising that a = b, no!

Let us rewrite Charles' law in the form

Considering that T = t°С + 273 °С, T 0 = 273 °C, we get

Temperature is a quantitative measure of the “warmth” of a body. The concept of temperature occupies a special place among the physical quantities that determine the state of the system. Temperature not only characterizes the state of thermal equilibrium of a given body. It is also the parameter that takes the same value for any two or more bodies located in thermal equilibrium with each other, i.e. characterizes the thermal equilibrium of a system of bodies. This means that if two or more bodies having different temperatures are brought into contact, then as a result of the interaction between molecules these bodies will take on the same temperature value.

The molecular kinetic theory makes it possible to clarify the physical meaning of temperature. Comparing expressions (2.4) and (2.7), we see that they coincide if we put

(2.9)

These relationships are called the second basic equations of the molecular kinetic theory of gases. They show that absolute temperature is the quantity that determines the average kinetic energy of the translational motion of molecules; it is a measure of the energy of translational motion of molecules, and thereby the intensity of thermal motion of molecules. This is the molecular kinetic meaning of absolute temperature. As we see, the process of heating a body is directly related to an increase in the average kinetic energy of the particles of the body. From (2.9) it is clear that absolute temperature is a positive quantity: Meaning called absolute zero temperature. According to (2.8), at absolute zero the translational motion of particles should completely stop ( ). It should be noted, however, that at low temperatures the gas becomes condensed. Consequently, all conclusions drawn on the basis of the kinetic theory of gases lose their meaning. And at absolute zero temperature, motion does not disappear. The movement of electrons in atoms and the movement of free electrons in metals are completely preserved even at absolute zero temperature. In addition, even at absolute zero, some vibrational motion of atoms inside molecules and atoms at the nodes of a crystal lattice is preserved. The existence of these oscillations is associated with the presence of zero-point energy in the quantum harmonic oscillator ( ), which can be considered the above vibrations of atoms. This energy does not depend on temperature, which means it does not vanish even at . At low temperatures, classical ideas about motion cease to hold true. In this area, quantum laws operate, according to which the movement of particles does not stop, even if the temperature of the body is reduced to absolute zero. But the speed of this movement no longer depends on temperature and this movement is not thermal. This is confirmed by the uncertainty principle. If the particles of the body were at rest, then their positions (coordinates x, y, z) and impulses (projections of impulse p x, p y, p z) would be precisely determined etc., and this contradicts the uncertainty relations etc. Absolute zero is not achievable. It will be shown below that absolute zero temperature means a state of the system in which the system is in a state with the lowest energy, and therefore a further decrease in the intensity of the movement of its particles due to the transfer of its energy to surrounding bodies is not possible.

Formula (2.7) can be written in the form.

This formula can serve as a definition of the concept of absolute temperature for a monatomic gas. The temperature of any other system can be defined as the value equal to temperature monatomic gas in thermal equilibrium with this system. The determination of temperature using this formula is correct up to temperatures at which the probability of the occurrence of electronically excited states of gas atoms can no longer be neglected.

Relation (2.8) allows us to introduce the so-called root mean square velocity of a molecule, defining it as

Then we get

The concept of absolute temperature can be more strictly introduced in statistical physics, where it can be considered as the modulus of the statistical distribution of particles by energy. Note also that since temperature, like pressure, as can be seen from formulas (2.7) and (2.8), is determined by the average kinetic energy of an ideal gas molecule, then they represent statistical quantities and, therefore, it makes no sense to talk about the temperature or pressure of one or a small number of molecules.

Absolute zero temperature

Absolute zero temperature(less often - absolute zero temperature) - the minimum temperature limit that a physical body in the Universe can have. Absolute zero serves as the origin of an absolute temperature scale, such as the Kelvin scale. In 1954, the X General Conference on Weights and Measures established a thermodynamic temperature scale with one reference point - the triple point of water, the temperature of which was taken to be 273.16 K (exact), which corresponds to 0.01 °C, so that on the Celsius scale the temperature corresponds to absolute zero −273.15 °C.

Phenomena observed near absolute zero

At temperatures close to absolute zero, purely quantum effects can be observed at the macroscopic level, such as:

Notes

Literature

G. Burmin. Assault on absolute zero. - M.: “Children’s Literature”, 1983

Absolute zero temperature and its physical meaning. Absolute zero

Notes

Literature

see also

See what “Absolute zero” is in other dictionaries:

Phenomena observed near absolute zero

Notes

Literature

see also

See what “Absolute zero temperature” is in other dictionaries: