Absolute zero. Absolute zero - (absolute zero)

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Federal State Budgetary Educational Institution of Higher Professional Education

"Voronezh State Pedagogical University"

Department of General Physics

on the topic: "Absolute zero temperature"

Completed by: 1st year student, FMF,

PI, Kondratenko Irina Aleksandrovna

Checked by: Assistant of the Department of General

physicists Afonin G.V.

Voronezh-2013

Introduction………………………………………………………. 3

1.Absolute zero…………………………………………...4

2.History……………………………………………………… 6

3. Phenomena observed near absolute zero………..9

Conclusion……………………………………………………… 11

List of used literature…………………………..12

Introduction

For many years, researchers have been attacking the absolute zero temperature. As you know, the temperature equal to absolute zero characterizes the ground state of a system of many particles - the state with the lowest possible energy, at which atoms and molecules perform the so-called "zero" vibrations. Thus, deep cooling close to absolute zero (it is believed that absolute zero itself is unattainable in practice) opens up unlimited possibilities for studying the properties of matter.

1. Absolute zero

Absolute zero temperature (more rarely - absolute zero temperature) is the minimum temperature limit that a physical body in the Universe can have. Absolute zero serves as the reference point for 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 is taken to be 273.16 K (exactly), which corresponds to 0.01 ° C, so that on the Celsius scale absolute zero corresponds to temperature -273.15°C.

In the framework of the applicability of thermodynamics, 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 (liquid helium is an exception). However, from the point of view of quantum physics, even at absolute zero temperature, there are zero fluctuations, which are due to the quantum properties of particles and the physical vacuum surrounding them.

As the temperature of the system tends to absolute zero, its entropy, heat capacity, thermal expansion coefficient also tend to zero, and the chaotic motion of the particles that make up the system stops. In a word, matter becomes supersubstance with superconductivity and superfluidity.

The absolute zero of temperature is unattainable in practice, and obtaining temperatures approaching it as close as possible is a complex experimental problem, but temperatures have already been obtained that are only millionths of a degree away from absolute zero. .

Let us find the value of absolute zero on the Celsius scale by equating the volume V to zero and taking into account that

Hence the absolute zero temperature is -273°C.

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

Fig.1. Absolute scale and Celsius scale

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 is a derivative quantity that depends 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 = 0 K, the thermal motion of molecules stops.

2. History

The physical concept of "absolute zero temperature" is very important for modern science: 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 as G. 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 the normal temperature of the human body, 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 the boiling point of 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. From this law, the obvious conclusion followed: the temperature equal to -273 ° C 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 law of thermodynamics, therefore, the absolute temperature scale introduced by him in 1848 began to be called the thermodynamic or “Kelvin scale.” In subsequent years and decades, only the numerical refinement of the concept of “absolute zero” took place.

Fig.2. Relationship between Fahrenheit (F), Celsius (C) and Kelvin (K) temperature scales.

It is also worth noting that absolute zero plays a very important role in the SI system. The thing is 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 degree Celsius, only here the reference point "according to Kelvin" is considered to be absolute zero.

The main physical meaning of absolute zero is that, according to the basic physical laws, at such a temperature, the energy of motion of elementary particles, such as atoms and molecules, is equal to zero, and in this case, any chaotic motion of these same particles should stop. At a temperature equal to absolute zero, atoms and molecules should 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.

3. Phenomena observed near absolute zero

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

1. Superconductivity - the property of some materials to have strictly zero electrical resistance when they reach a temperature below a certain value (critical temperature). Several hundreds of compounds, pure elements, alloys and ceramics are known that pass into the superconducting state.

Superconductivity is a quantum phenomenon. It is also characterized by the Meissner effect, which consists in the complete displacement of the magnetic field from the bulk of the superconductor. The existence of this effect shows that superconductivity cannot be described simply as ideal conductivity in the classical sense. Opening in 1986-1993 a number of high-temperature superconductors (HTSCs) pushed far the temperature limit of superconductivity and allowed the practical use of superconducting materials not only at the temperature of liquid helium (4.2 K), but also at the boiling point of liquid nitrogen (77 K), a much cheaper cryogenic liquid.

2. Superfluidity - the ability of a substance in a special state (quantum liquid), which occurs when the temperature drops to absolute zero (thermodynamic phase), to flow through narrow slots and capillaries without friction. Until recently, superfluidity was known only for liquid helium, but in recent years superfluidity has also been discovered in other systems: in rarefied atomic Bose condensates and solid helium.

Superfluidity is explained as follows. Since helium atoms are bosons, quantum mechanics allows an arbitrary number of particles to be in the same state. Near absolute zero temperatures, all helium atoms are in the ground energy state. Since the energy of the states is discrete, an atom can receive not any energy, but only one that is equal to the energy gap between neighboring energy levels. But at low temperatures, the collision energy may be less than this value, as a result of which energy dissipation simply will not occur. The fluid will flow without friction.

3. The Bose-Einstein condensate is an aggregate state of matter based on bosons cooled to temperatures close to absolute zero (less than a millionth of a degree above absolute zero). In such a strongly cooled state, a sufficiently large number of atoms find themselves in their minimum possible quantum states, and quantum effects begin to manifest themselves at the macroscopic level.

Conclusion

The study of the properties of matter near absolute zero is of great interest to science and technology.

Many properties of a substance, veiled at room temperature by thermal phenomena (for example, thermal noise), begin to manifest themselves more and more as the temperature decreases, allowing one to study in its pure form the regularities and relationships inherent in a given substance. Research in the field of low temperatures made it possible to discover many new natural phenomena, such as, for example, the superfluidity of helium and the superconductivity of metals.

At low temperatures, the properties of materials change dramatically. Some metals increase their strength, become ductile, others become brittle, like glass.

The study of physicochemical properties at low temperatures will make it possible in the future to create new substances with predetermined properties. All this is very valuable for the design and construction of spacecraft, stations and instruments.

It is known that during radar studies of cosmic bodies, the received radio signal is very small and it is difficult to distinguish it from various noises. Molecular oscillators and amplifiers recently created by scientists operate at very low temperatures and therefore have a very low noise level.

The low-temperature electrical and magnetic properties of metals, semiconductors and dielectrics make it possible to develop fundamentally new radio engineering devices of microscopic dimensions.

Extremely low temperatures are used to create the vacuum required, for example, for the operation of giant nuclear particle accelerators.

Bibliography

http://wikipedia.org
http://rudocs.exdat.com
http://fb.ru

Short description

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 gas mass 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.

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.

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 that determine 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 value of absolute zero temperatures is equal to −273.15 ° C.

Using temperature values in the Kelvin scale according to the same International System of Units, boiling water will occur at a reference value of 99.975 ° C, absolute zero equates to 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 both on the transmission wavelength, and on the conditions, and on the necessary absorption of a large amount of energy by the particles. 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 extremely low temperature 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.

Where do you think the coldest place in our universe is located? Today it is Earth. For example, the surface temperature of the moon is -227 degrees Celsius, and the temperature of the vacuum that surrounds us is 265 degrees below zero. However, in a laboratory on Earth, a person can achieve temperatures much lower in order to study the properties of materials in ultra-low temperatures. Materials, individual atoms, and even light subjected to extreme cooling begin to exhibit unusual properties.

The first experiment of this kind was carried out at the beginning of the 20th century by physicists who studied the electrical properties of mercury at ultralow temperatures. At -262 degrees Celsius, mercury begins to exhibit the properties of superconductivity, reducing the resistance to electric current to almost zero. Further experiments also revealed other interesting properties of cooled materials, including superfluidity, which is expressed in the "leakage" of matter through solid partitions and out of closed containers.

Science has determined the lowest achievable temperature - minus 273.15 degrees Celsius, but practically such a temperature is unattainable. In practice, temperature is an approximate measure of the energy contained in an object, so absolute zero indicates that the body does not radiate anything, and no energy can be extracted from this object. But despite this, scientists are trying to get as close as possible to absolute zero temperature, the current record was set in 2003 in the laboratory of the Massachusetts Institute of Technology. Scientists were only 810 billionths of a degree short of absolute zero. They cooled a cloud of sodium atoms held in place by a powerful magnetic field.

It would seem - what is the applied meaning of such experiments? It turns out that researchers are interested in such a concept as the Bose-Einstein condensate, which is a special state of matter - not a gas, solid or liquid, but simply a cloud of atoms with the same quantum state. This form of matter was predicted by Einstein and the Indian physicist Satyendra Bose in 1925, and was obtained only 70 years later. One of the scientists who achieved this state of matter is Wolfgang Ketterle, who received the Nobel Prize in Physics for his discovery.

One of the remarkable properties of the Bose-Einstein Condensate (BEC) is the ability to control the movement of light rays. In a vacuum, light travels at 300,000 km per second, which is the fastest speed achievable in the universe. But light can propagate more slowly if it propagates not in a vacuum, but in matter. With the help of BEC, it is possible to slow down the movement of light to low speeds, and even stop it. Due to the temperature and density of the condensate, the light emission slows down and can be "captured" and converted directly into electrical current. This current can be transferred to another BEC cloud and converted back into light radiation. This feature is in great demand for telecommunications and computing. Here I don’t understand a bit - after all, there are ALREADY devices that convert light waves into electricity and vice versa ... Apparently, the use of BEC allows this conversion to be done faster and more accurately.

One of the reasons why scientists are so eager to get an absolute zero is an attempt to understand what is happening and has happened to our Universe, what thermodynamic laws operate in it. At the same time, researchers understand that extracting all the energy to the last from the atom is practically unattainable.

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Absolute zero. Absolute zero - (absolute zero)

Notes

Literature

see also

See what "Absolute Zero" is in other dictionaries:

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

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