Absolute zero temperatures

Absolute zero temperature is the minimum temperature limit that can be physical body. Absolute zero serves as the reference point for an absolute temperature scale, such as the Kelvin scale. On the Celsius scale, absolute zero corresponds to -273.15 °C.

It is believed that absolute zero is unattainable in practice. Its existence and position on the temperature scale follows from the extrapolation of the observed physical phenomena, while such extrapolation shows that at absolute zero, the energy of the thermal motion of molecules and atoms of a substance must be equal to zero, that is, the chaotic motion 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 fluctuations, such as zero-point vibrations, are due to the quantum properties of the particles and the physical vacuum that surrounds them.

Currently in physical laboratories it was possible to obtain a temperature exceeding absolute zero by only a few millionths of a degree; it is impossible to achieve it, according to the laws of thermodynamics.

Notes

Literature

G. Burmin. Storming absolute zero. - M .: "Children's literature", 1983.

Kelvin scale

Kelvin William (Thomson W.) (1824-1907) - an outstanding English physicist, one of the founders of thermodynamics and the molecular-kinetic theory of gases.

Kelvin introduced the absolute temperature scale and gave one of the formulations of the second law of thermodynamics in the form of the impossibility of complete conversion of heat into work. He calculated the size of molecules based on the measurement of the surface energy of a liquid. In connection with the laying of the transatlantic telegraph cable, Kelvin developed the theory of electromagnetic oscillations and derived a formula for the period of free oscillations in the circuit. For scientific merits, W. Thomson received the title of Lord Kelvin.

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

(3.7.6)

Figure 3.11 shows the absolute scale and the Celsius scale for comparison.

The SI unit of absolute temperature is called the kelvin (abbreviated as K). Therefore, one degree Celsius is equal to one degree Kelvin: 1 °C = 1 K.

Thus, the absolute temperature, by definition given by formula (3.7.6), is a derivative quantity depending on the Celsius temperature and on the experimentally determined value of a. However, it is of fundamental importance.

From the point of view of the molecular kinetic theory, the absolute temperature is related to the average kinetic energy of the random motion of atoms or molecules. At T = About To the thermal motion of molecules stops. This will be discussed in more detail in Chapter 4.

Volume versus absolute temperature

Using the Kelvin scale, the Gay-Lussac law (3.6.4) can be written in a simpler form. Because

(3.7.7)

The volume of a gas of a given mass at constant pressure is directly proportional to the absolute temperature.

It follows that the ratio of gas volumes of the same mass in different states at the same pressure is equal to the ratio of absolute temperatures:

(3.7.8)

There is a minimum possible temperature at which the volume (and pressure) of an ideal gas vanishes. This is absolute zero temperature:-273 °С. It is convenient to measure the temperature from absolute zero. This is how the absolute temperature scale is built.

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 the extrapolation of the observed physical phenomena, while such extrapolation shows that at absolute zero, the energy of the thermal motion of molecules and atoms of a substance must be equal to zero, that is, the chaotic motion of particles stops, and they form an ordered structure, occupying a clear position in 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 fluctuations, such as zero-point vibrations, are due to the quantum properties of the particles and the physical vacuum that surrounds them.

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

Notes

Literature

G. Burmin. Storming absolute zero. - M .: "Children's literature", 1983.

absolute zero temperature

The limiting temperature at which the volume of an ideal gas becomes 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) to zero and taking into account that

Hence the absolute zero temperature is

t= -273 °С. 2

This is the limiting, 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 more high temperatures characteristic of the inner regions of some stars.

2More exact value absolute zero: -273.15 °С.

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 degrees Celsius, so the absolute temperature T is related to temperature on the Celsius scale by the formula

T = t + 273. (3.2)

On 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 Celsius equals one degree Kelvin:

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

Reader: Which one then physical meaning has an absolute temperature?

We write expression (3.1) in the form

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

Where T 0 = 273 K, or

Since this relation is valid for an arbitrary temperature T, then the Gay-Lussac law can be formulated as follows:

For a given mass of gas at p = const, the relation

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.

Task 3.2. With isobaric heating, the volume of air increased by 1%. By what percent did the absolute temperature increase?

= 0,01.

Answer: 1 %.

Remember the resulting formula

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

Charles' law

The French scientist Charles experimentally found that if you heat a gas so that its volume remains constant, then 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) is 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, keeping the pressure of the gas constant, we heat it to a temperature T 1 . Then the gas will have volume V 1 = V 0 (1 + a t) and pressure R 0 .

The second time, keeping the volume of the 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 the gas temperature is the same in both cases, 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 there is nothing surprising in the fact that a = b, no!

Let us rewrite Charles's law in the form

Given that T = t°С + 273 °С, T 0 \u003d 273 ° С, we get

ABSOLUTE ZERO

ABSOLUTE ZERO, the temperature at which all components of the system have the least amount of energy allowed by the laws of QUANTUM MECHANICS; zero on the Kelvin temperature scale, or -273.15 ° C (-459.67 ° Fahrenheit). At this temperature, the entropy of the system - the amount of energy available for doing useful work - is also zero, although total the energy of the system can be different from zero.

Scientific and technical encyclopedic dictionary.

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Razg. Neglect An insignificant, insignificant person. FSRYA, 288; BTS, 24; ZS 1996, 33 ...

zero- absolute zero … Dictionary of Russian Idioms

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Absolute Zero, Absolute Pavel. The life of all the creations of the mad scientist of the nes race is very short. But the next experiment has a chance to exist. What lies ahead for him?...

Absolute zero on the Kelvin scale. A. Absolute zero

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Kelvin scale

Volume versus absolute temperature

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absolute zero temperature

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