Absolute zero temperature on the Celsius scale. Absolute zero: history of discovery and main application

Any physical body, including all objects in the universe, has a minimum temperature index or its limit. For the reference point of any temperature scale, it is customary to consider the value of absolute zero temperatures. But this is only in theory. The chaotic movement of atoms and molecules, which give off their energy at this time, has not yet been stopped in practice.

This is the main reason why absolute zero temperatures cannot be reached. There are still disputes about the consequences of this process. From the point of view of thermodynamics, this limit is unattainable, since the thermal motion of atoms and molecules stops completely, and a crystal lattice is formed.

Representatives of quantum physics provide for the presence of minimal zero-point oscillations at absolute zero temperatures.

What is the value of absolute zero temperature and why it cannot be reached

At the General Conference on Weights and Measures, for the first time, a reference or reference point was established for measuring instruments, which determine the temperature indicators.

Currently, in the International System of Units, the reference point for the Celsius scale is 0°C when freezing and 100°C during the boiling process, the absolute zero temperature value is equal to −273.15°C.

Using temperature values ​​on the Kelvin scale in the same International System of Units, water will boil at reference value 99.975°C, absolute zero equals 0. Fahrenheit on the scale corresponds to -459.67 degrees.

But, if these data are obtained, why then it is impossible to achieve absolute zero temperatures in practice. For comparison, we can take the speed of light known to everyone, which is equal to a constant physical value of 1,079,252,848.8 km/h.

However, this value cannot be achieved in practice. It depends on the transmission wavelength, and on the conditions, and on the required absorption a large number particle energy. To obtain the value of absolute zero temperatures, a large return of energy is necessary and the absence of its sources to prevent it from entering atoms and molecules.

But even in conditions of complete vacuum, neither the speed of light nor absolute zero temperatures were obtained by scientists.

Why is it possible to reach approximate zero temperatures, but not absolute

What will happen when science can come close to achieving the lowest temperature index of absolute zero, so far remains only in the theory of thermodynamics and quantum physics. What is the reason why it is impossible to reach absolute zero temperatures in practice.

All known attempts to cool the substance to the lowest limit limit due to the maximum energy loss led to the fact that the value of the heat capacity of the substance also reached a minimum value. Molecules were simply not able to give the rest of the energy. As a result, the cooling process stopped before reaching absolute zero.

When studying the behavior of metals in conditions close to the value of absolute zero temperatures, scientists have found that the maximum decrease in temperature should provoke a loss of resistance.

But the cessation of the movement of atoms and molecules only led to the formation of a crystal lattice through which the passing electrons transferred part of their energy to the immobile atoms. It failed to reach absolute zero again.

In 2003, only half a billionth of 1°C was missing from absolute zero. NASA researchers used the Na molecule to conduct experiments, which was always in a magnetic field and gave off its energy.

The closest was the achievement of scientists from Yale University, which in 2014 achieved an indicator of 0.0025 Kelvin. The resulting compound strontium monofluoride (SrF) existed for only 2.5 seconds. And in the end, it still fell apart into atoms.

Absolute zero(absolute zero) - the beginning of the absolute temperature, starting from 273.16 K below the triple point of water (the equilibrium point of three phases - ice, water and water vapor); at absolute zero, the motion of molecules stops, and they are in a state of "zero" motions. Or: the lowest temperature at which a substance contains no thermal energy.

Absolute zero Start absolute temperature reading. Corresponds to -273.16 ° C. At present, physical laboratories have managed to obtain a temperature exceeding absolute zero by only a few millionths of a degree, but according to the laws of thermodynamics, it is impossible to achieve it. At absolute zero, the system would be in a state with the lowest possible energy (in this state, atoms and molecules would make "zero" vibrations) and have zero entropy (zero disorder). The volume of an ideal gas at the point of absolute zero must be equal to zero, and to determine this point, the volume of real helium gas is measured at consistent lowering the temperature until it liquefies at low pressure (-268.9 ° C) and extrapolates to the temperature at which the volume of the gas would go to zero in the absence of liquefaction. Absolute temperature thermodynamic The scale is measured in kelvins, denoted by the symbol K. Absolute thermodynamic the scale and the Celsius scale are simply shifted relative to each other and are related by the relation K = °C + 273.16 °.

History

The word "temperature" arose at a time when people believed that hotter bodies contained a greater amount of a special substance - caloric than less heated ones. Therefore, temperature was perceived as the strength of a mixture of body substance and caloric. For this reason, the units of measure for the strength of alcoholic beverages and temperature are called the same - degrees.

From the fact that temperature is the kinetic energy of molecules, it is clear that it is most natural to measure it in energy units (i.e. in the SI system in joules). However, temperature measurement began long before the creation of the molecular kinetic theory, so practical scales measure temperature in conventional units - degrees.

Kelvin scale

In thermodynamics, the Kelvin scale is used, in which the temperature is measured from absolute zero (the state corresponding to the minimum theoretically possible internal energy body), and one kelvin is equal to 1/273.16 of the distance from absolute zero to the triple point of water (the state in which ice, water and water vapor are in equilibrium). The Boltzmann constant is used to convert kelvins to energy units. Derived units are also used: kilokelvin, megakelvin, millikelvin, etc.

Celsius

In everyday life, the Celsius scale is used, in which the freezing point of water is taken as 0, and the boiling point of water at atmospheric pressure is taken as 100 °. Since the freezing and boiling points of water are not well defined, the Celsius scale is currently defined in terms of the Kelvin scale: degrees Celsius equals Kelvin, absolute zero is taken to be −273.15 °C. The Celsius scale is practically very convenient, since water is very common on our planet and our life is based on it. Zero Celsius is a special point for meteorology, since the freezing of atmospheric water changes everything significantly.

Fahrenheit

In England, and especially in the USA, the Fahrenheit scale is used. In this scale, the interval is divided by 100 degrees from the temperature of the cold winter in the city where Fahrenheit lived, to the temperature of a human body. Zero degrees Celsius is 32 degrees Fahrenheit, and a degree Fahrenheit is 5/9 degrees Celsius.

The current definition of the Fahrenheit scale is: temperature scale, 1 degree of which (1 °F) is equal to 1/180 of the difference between the boiling point of water and the melting of ice at atmospheric pressure, and the melting point of ice is +32 °F. The temperature on the Fahrenheit scale is related to the temperature on the Celsius scale (t ° C) by the ratio t ° C = 5/9 (t ° F - 32), 1 ° F = 5/9 ° C. Proposed by G. Fahrenheit in 1724.

Reaumur scale

Proposed in 1730 by R. A. Reaumur, who described the alcohol thermometer he invented.

Unit - degree Réaumur (°R), 1 °R is equal to 1/80 of the temperature interval between the reference points - the temperature of melting ice (0 °R) and boiling water (80 °R)

1°R = 1.25°C.

At present, the scale has fallen into disuse; it has been preserved for the longest time in France, in the author's homeland.

Comparison of temperature scales

Normal human body temperature is 36.6 °C ±0.7 °C, or 98.2 °F ±1.3 °F. The commonly given value of 98.6 °F is an exact Fahrenheit conversion of the 19th century German value of 37 °C. Because this value is outside the normal temperature range for modern ideas, we can say that it contains excessive (incorrect) precision. Some values ​​in this table have been rounded.

Comparison of Fahrenheit and Celsius scales

(oF- Fahrenheit scale, o C- Celsius scale)

To convert degrees Celsius to kelvins, use the formula T=t+T0 where T is the temperature in kelvins, t is the temperature in degrees Celsius, T 0 =273.15 kelvin. A degree Celsius is equal in size to a kelvin.

The physical concept of "absolute zero temperature" has for modern science very important: such a concept as superconductivity, the discovery of which made a splash in the second half of the 20th century, is closely related to it.

To understand what absolute zero is, one should refer to the works of such famous physicists, like H. Fahrenheit, A. Celsius, J. Gay-Lussac and W. Thomson. It was they who played a key role in the creation of the main temperature scales still used today.

The first to offer his own temperature scale in 1714 was the German physicist G. Fahrenheit. At the same time, the temperature of the mixture, which included snow and ammonia, was taken as absolute zero, that is, the lowest point on this scale. The next important indicator was which began to equal 1000. Accordingly, each division of this scale was called the “degree Fahrenheit”, and the scale itself was called the “Fahrenheit scale”.

After 30 years, the Swedish astronomer A. Celsius proposed his own temperature scale, where the main points were the melting temperature of ice and water. This scale was called the "Celsius scale", it is still popular in most countries of the world, including Russia.

In 1802, while conducting his famous experiments, the French scientist J. Gay-Lussac discovered that the volume of a mass of gas at constant pressure is directly dependent on temperature. But the most curious thing was that when the temperature changed by 10 Celsius, the volume of the gas increased or decreased by the same amount. Having made the necessary calculations, Gay-Lussac found that this value was equal to 1/273 of the volume of gas at a temperature equal to 0C.

The obvious conclusion followed from this law: the temperature equal to -2730C is the lowest temperature, even approaching which it is impossible to reach it. This temperature is called "absolute zero temperature".

Moreover, absolute zero became the starting point for creating the absolute temperature scale, in which the English physicist W. Thomson, also known as Lord Kelvin, took an active part.

His main research concerned the proof that no body in nature can be cooled below absolute zero. At the same time, he actively used the second one, therefore, the absolute temperature scale introduced by him in 1848 became known as the thermodynamic or "Kelvin scale".

In subsequent years and decades, only a numerical refinement of the concept of "absolute zero" took place, which, after numerous agreements, began to be considered equal to -273.150C.

It is also worth noting that absolute zero plays a very important role in the whole fact that in 1960 at the next General Conference on Weights and Measures, the unit of thermodynamic temperature - kelvin - became one of the six basic units of measurement. At the same time, it was specifically stipulated that one degree Kelvin is numerically equal to one, only here the reference point “according to Kelvin” is considered to be absolute zero, that is, -273.150С.

The main physical meaning of absolute zero is that, according to the basic physical laws, at this temperature the energy of motion elementary particles, such as atoms and molecules, is equal to zero, and in this case, any chaotic movement of these very particles should stop. At a temperature equal to absolute zero, atoms and molecules must take a clear position in the main points of the crystal lattice, forming an ordered system.

Currently, using special equipment, scientists have been able to obtain a temperature only a few millionths higher than absolute zero. It is physically impossible to achieve this value itself because of the second law of thermodynamics described above.

The term "temperature" appeared at a time when physicists thought that warm bodies were composed of more specific substance - caloric - than the same bodies, but cold. And the temperature was interpreted as a value corresponding to the amount of caloric in the body. Since then, the temperature of any body is measured in degrees. But in reality it is a measure of the kinetic energy of moving molecules, and, based on this, it should be measured in Joules, in accordance with the SI system of units.

The concept of "absolute zero temperature" comes from the second law of thermodynamics. According to it, the process of transferring heat from a cold body to a hot one is impossible. This concept was introduced by the English physicist W. Thomson. For achievements in physics, he was granted the noble title of "Lord" and the title of "Baron Kelvin". In 1848, W. Thomson (Kelvin) suggested using a temperature scale, in which he took the absolute zero temperature corresponding to the extreme cold as the starting point, and took degrees Celsius as the division price. The unit of Kelvin is 1/27316 of the temperature of the triple point of water (about 0 degrees C), i.e. the temperature at which pure water exists in three forms at once: ice, liquid water, and steam. temperature is the lowest possible low temperature at which the movement of molecules stops, and it is no longer possible to extract thermal energy from the substance. Since then, the absolute temperature scale has been named after him.

Temperature is measured on different scales

The most commonly used temperature scale is called the Celsius scale. It is built on two points: on the temperature of the phase transition of water from liquid to vapor and water to ice. A. Celsius in 1742 proposed to divide the distance between reference points into 100 intervals, and take water as zero, while the freezing point is 100 degrees. But the Swede K. Linnaeus suggested doing the opposite. Since then, water freezes at zero degrees A. Celsius. Although it should boil exactly in Celsius. Absolute zero in Celsius corresponds to minus 273.16 degrees Celsius.

There are several more temperature scales: Fahrenheit, Réaumur, Rankine, Newton, Roemer. They have different and price divisions. For example, the Réaumur scale is also built on the benchmarks of boiling and freezing of water, but it has 80 divisions. The Fahrenheit scale, which appeared in 1724, is used in everyday life only in some countries of the world, including the USA; one is the temperature of the mixture of water ice - ammonia and the other is the temperature of the human body. The scale is divided into one hundred divisions. Zero Celsius corresponds to 32 The conversion of degrees to Fahrenheit can be done using the formula: F \u003d 1.8 C + 32. Reverse translation: C \u003d (F - 32) / 1.8, where: F - degrees Fahrenheit, C - degrees Celsius. If you are too lazy to count, go to the online Celsius to Fahrenheit conversion service. In the box, type the number of degrees Celsius, click "Calculate", select "Fahrenheit" and click "Start". The result will appear immediately.

Named after the English (more precisely Scottish) physicist William J. Rankin, a former contemporary of Kelvin and one of the founders of technical thermodynamics. There are three important points in his scale: the beginning is absolute zero, the freezing point of water is 491.67 degrees Rankine and the boiling point of water is 671.67 degrees. The number of divisions between the freezing of water and its boiling in both Rankine and Fahrenheit is 180.

Most of these scales are used exclusively by physicists. And 40% of American high school students surveyed these days said they don't know what absolute zero temperature is.

Absolute zero temperature

Absolute zero temperature is the minimum temperature limit that a physical body can have. 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 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 oscillations, such as zero oscillations, are due to quantum properties particles and the physical vacuum surrounding 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.

see also

Wikimedia Foundation. 2010 .

• Absolute zero temperature
• Absolute zero temperature

See what "Absolute Zero Temperature" is in other dictionaries:

Absolute zero temperature- Absolute zero temperature is the minimum temperature limit that a physical body can have. Absolute zero is the starting point for an absolute temperature scale, such as the Kelvin scale. On the Celsius scale, absolute zero corresponds to ... ... Wikipedia

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... Scientific and technical encyclopedic dictionary

Absolute temperature scale

Absolute thermodynamic temperature- Chaotic thermal motion on the plane of gas particles such as atoms and molecules There are two definitions of temperature. One from a molecular kinetic point of view, the other from a thermodynamic point of view. Temperature (from Latin temperatura proper ... ... Wikipedia

Absolute temperature scale- Chaotic thermal motion on the plane of gas particles such as atoms and molecules There are two definitions of temperature. One from a molecular kinetic point of view, the other from a thermodynamic point of view. Temperature (from Latin temperatura proper ... ... Wikipedia