There are several different units for measuring temperature.

The most famous are the following:

Degree Celsius - used in the International System of Units (SI) along with kelvin.

The degree Celsius is named after the Swedish scientist Anders Celsius, who proposed a new scale for measuring temperature in 1742.

The original definition of degrees Celsius depended on the definition of standard atmospheric pressure because both the boiling point of water and the melting point of ice depend on pressure. This is not very convenient for standardizing the unit of measurement. Therefore, after the adoption of the Kelvin K as the basic unit of temperature, the definition of the degree Celsius was revised.

According to modern definition, a degree Celsius is equal to one kelvin K, and the zero of the Celsius scale is set so that the temperature of the triple point of water is 0.01 °C. As a result, the Celsius and Kelvin scales are shifted by 273.15:

In 1665, the Dutch physicist Christiaan Huygens, together with the English physicist Robert Hooke, first proposed using the melting points of ice and boiling water as reference points on the temperature scale.

In 1742, the Swedish astronomer, geologist and meteorologist Anders Celsius (1701-1744) developed a new temperature scale based on this idea. Initially, 0° (zero) was the boiling point of water, and 100° was the freezing point of water (melting point of ice). Later, after the death of Celsius, his contemporaries and compatriots, botanist Carl Linnaeus and astronomer Morten Stremer, used this scale inverted (they began to take the melting temperature of ice as 0°, and the boiling of water as 100°). This is the form in which the scale is used to this day.

According to some sources, Celsius himself turned his scale upside down on the advice of Stremer. According to other sources, the scale was turned over by Carl Linnaeus in 1745. And according to the third, the scale was turned upside down by Celsius’ successor Morten Stremer, and in the 18th century such a thermometer was widely distributed under the name “Swedish thermometer”, and in Sweden itself - under the name Stremer, but the famous Swedish chemist Jons Jacob Berzelius in his work “Manual of Chemistry” "named the scale "Celsius" and since then the centigrade scale began to bear the name of Anders Celsius.

Degree Fahrenheit.

Named after the German scientist Gabriel Fahrenheit, who proposed a scale for measuring temperature in 1724.

On the Fahrenheit scale, the melting point of ice is +32 °F and the boiling point of water is +212 °F (at normal atmospheric pressure). Moreover, one degree Fahrenheit is equal to 1/180 of the difference between these temperatures. The 0...+100°F Fahrenheit range roughly corresponds to the -18...+38°C Celsius range. Zero on this scale is determined by the freezing point of a mixture of water, salt and ammonia (1:1:1), and 96 °F is the normal temperature of the human body.

Kelvin (before 1968 degree Kelvin) is a unit of thermodynamic temperature in the International System of Units (SI), one of the seven base SI units. Proposed in 1848. 1 kelvin is equal to 1/273.16 of the thermodynamic temperature of the triple point of water. The beginning of the scale (0 K) coincides with absolute zero.

Conversion to degrees Celsius: °C = K−273.15 (temperature of the triple point of water - 0.01 °C).

The unit is named after the English physicist William Thomson, who was given the title Lord Kelvin of Larg of Ayrshire. In turn, this title comes from the River Kelvin, which flows through the territory of the university in Glasgow.

Degree of Reaumur - a unit of measurement of temperature in which the freezing and boiling points of water are taken to be 0 and 80 degrees, respectively. Proposed in 1730 by R. A. Reaumur. The Reaumur scale has practically fallen out of use.

Roemer's degree - a currently unused unit of temperature.

The Römer temperature scale was created in 1701 by the Danish astronomer Ole Christensen Römer. It became the prototype of the Fahrenheit scale, which visited Roemer in 1708.

Zero degrees is the freezing point of salt water. The second reference point is the temperature of the human body (30 degrees according to Roemer’s measurements, that is, 42 °C). Then the freezing point of fresh water is 7.5 degrees (1/8 scale), and the boiling point of water is 60 degrees. Thus, the Roemer scale is 60 degrees. This choice seems to be explained by the fact that Roemer is primarily an astronomer, and the number 60 has been the cornerstone of astronomy since Babylon.

Rankin degree - a unit of temperature on the absolute temperature scale, named after the Scottish physicist William Rankin (1820-1872). Used in English-speaking countries for engineering thermodynamic calculations.

The Rankine scale begins at absolute zero, the freezing point of water is 491.67°Ra, the boiling point of water is 671.67°Ra. The number of degrees between the freezing and boiling points of water on the Fahrenheit and Rankine scales is the same and equal to 180.

The relationship between Kelvin and Rankine is 1 K = 1.8 °Ra, Fahrenheit is converted to Rankine using the formula °Ra = °F + 459.67.

Degree Delisle - a currently unused unit of temperature measurement. It was invented by the French astronomer Joseph Nicolas Delisle (1688-1768). The Delisle scale is similar to the Reaumur temperature scale. Used in Russia until the 18th century.

Peter the Great invited the French astronomer Joseph Nicolas Delisle to Russia, establishing the Academy of Sciences. In 1732, Delisle created a thermometer using mercury as the working fluid. The boiling point of water was chosen as zero. A change in temperature was taken as one degree, which led to a decrease in the volume of mercury by one hundred thousandth.

Thus, the melting temperature of the ice was 2400 degrees. However, later such a fractional scale seemed redundant, and already in the winter of 1738 Delisle’s colleague at the St. Petersburg Academy, physician Josias Weitbrecht (1702-1747), reduced the number of steps from the boiling point to the freezing point of water to 150.

The “inversion” of this scale (as well as the original version of the Celsius scale) in comparison with those currently accepted is usually explained by purely technical difficulties associated with the calibration of thermometers.

Delisle's scale became quite widespread in Russia, and his thermometers were used for about 100 years. This scale was used by many Russian academics, including Mikhail Lomonosov, who, however, “inverted” it, placing zero at the freezing point, and 150 degrees at the boiling point of water.

Hooke's degree - historical unit of temperature. The Hooke scale is considered the very first temperature scale with a fixed zero.

The prototype for the scale created by Hooke was a thermometer from Florence that came to him in 1661. In Hooke's Micrographia, published a year later, there is a description of the scale he developed. Hooke defined one degree as a change in the volume of alcohol by 1/500, i.e. one degree of Hooke is equal to approximately 2.4 °C.

In 1663, the members of the Royal Society agreed to use Hooke's thermometer as a standard and compare the readings of other thermometers with it. The Dutch physicist Christiaan Huygens in 1665, together with Hooke, proposed using the temperatures of ice melting and water boiling to create a temperature scale. This was the first scale with a fixed zero and negative values.

Degree Dalton – historical unit of temperature. It does not have a specific value (in units of traditional temperature scales such as Kelvin, Celsius or Fahrenheit) because the Dalton scale is logarithmic.

The Dalton scale was developed by John Dalton for making measurements at high temperatures because conventional thermometers with a uniform scale erred due to the uneven expansion of the thermometric liquid.

Zero on the Dalton scale corresponds to zero Celsius. A distinctive feature of the Dalton scale is that its absolute zero is − ∞°Da, i.e. it is an unattainable value (which is actually the case, according to Nernst’s theorem).

Degree Newton - a unit of temperature not currently used.

The Newtonian temperature scale was developed by Isaac Newton in 1701 to conduct thermophysical research and was probably the prototype of the Celsius scale.

Newton used linseed oil as a thermometric fluid. Newton took the freezing point of fresh water to be zero degrees, and he designated the temperature of the human body as 12 degrees. Thus, the boiling point of water became 33 degrees.

Leiden degree is a historical unit of temperature used in the early 20th century to measure cryogenic temperatures below −183 °C.

This scale comes from Leiden, where the Kamerlingh Onnes laboratory has been located since 1897. In 1957, H. van Dijk and M. Durau introduced the L55 scale.

The boiling point of standard liquid hydrogen (−253 °C), consisting of 75% orthohydrogen and 25% parahydrogen, was taken as zero degrees. The second reference point is the boiling point of liquid oxygen (−193 °C).

Planck temperature , named after the German physicist Max Planck, is a unit of temperature, denoted T P , in the Planck system of units. This is one of the Planck units, which represents the fundamental limit in quantum mechanics. Modern physical theory is unable to describe anything hotter due to the lack of a developed quantum theory of gravity. Above the Planck temperature, the energy of particles becomes so great that the gravitational forces between them become comparable to other fundamental interactions. This is the temperature of the Universe at the first moment (Planck time) of the Big Bang in accordance with current concepts of cosmology.

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kelvin degrees Celsius degrees Fahrenheit degrees Rankine degrees Reaumur Planck temperature

More about temperature

General information

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The paradox is that in order to measure temperature in everyday life, industry, and even in applied science, you do not need to know what “temperature” is. The rather vague idea that “temperature is the degree heating bodies." Indeed, most practical instruments for measuring temperature actually measure other properties of substances that vary with this degree of heating, such as pressure, volume, electrical resistance, etc. Then their readings are automatically or manually converted into temperature units.

Curious people and students who either want or are forced to figure out what temperature is usually fall into the element of thermodynamics with its zeroth, first and second laws, the Carnot cycle and entropy. It must be admitted that the definition of temperature as a parameter of an ideal reversible heat engine, independent of the working substance, usually does not add clarity to our sense of the concept of “temperature”.

More “tangible” seems to be the approach called molecular kinetic theory, from which the idea is formed that heat can be considered simply as one of the forms of energy, namely the kinetic energy of atoms and molecules. This value, averaged over a huge number of randomly moving particles, turns out to be a measure of what is called body temperature. Particles of a heated body move faster than those of a cold body.

Since the concept of temperature is closely related to the average kinetic energy of particles, it would be natural to use the joule as its measurement unit. However, the energy of thermal motion of particles is very small compared to the joule, so the use of this quantity is inconvenient. Thermal motion is measured in other units, which are derived from joules using the conversion factor "k".

If temperature T is measured in kelvins (K), then its relationship with the average kinetic energy of translational motion of atoms of an ideal gas has the form

Ek = (3/2) kT, (1)

Where k- a conversion factor that determines what part of a joule is contained in a kelvin. Magnitude k called Boltzmann's constant.

Considering that pressure can also be expressed in terms of the average energy of molecular motion

p=(2/3)n E k (2)

Where n = N/V, V- volume occupied by gas, N- total number of molecules in this volume

The equation of state for an ideal gas will be:

p = n kT

If the total number of molecules is represented as N = µN A, Where µ - number of moles of gas, N A- Avagadro number, i.e. the number of particles per mole, you can easily obtain the well-known Clapeyron-Mendeleev equation:

pV = µ RT, where R - molar gas constant R= N A .k

or for one mole pV = N A . kT(3)

Thus, temperature is a parameter artificially introduced into the equation of state. Using the equation of state, the thermodynamic temperature T can be determined if all other parameters and constants are known. From this definition of temperature it is obvious that the values ​​of T will depend on the Boltzmann constant. Can we choose an arbitrary value for this proportionality coefficient and then rely on it? No. After all, we can thus obtain an arbitrary value for the triple point of water, while we should obtain a value of 273.16 K! The question arises - why exactly 273.16 K?

The reasons for this are purely historical, not physical. The fact is that in the first temperature scales, exact values ​​were adopted for two states of water at once - the solidification point (0 ° C) and the boiling point (100 ° C). These were arbitrary values ​​chosen for convenience. Considering that a degree Celsius is equal to a degree Kelvin and measuring the thermodynamic temperature with a gas thermometer calibrated at these points, we obtained a value for absolute zero (0 °K) by extrapolation - 273.15 °C. Of course, this value can only be considered accurate if the measurements with a gas thermometer were absolutely accurate. This is wrong. Therefore, by fixing the value of 273.16 K for the triple point of water, and measuring the boiling point of water with a more advanced gas thermometer, you can obtain a slightly different value for boiling from 100 ° C. For example, now the most realistic value is 99.975 °C. And this is only because early work with a gas thermometer gave an erroneous value for absolute zero. Thus, we either fix absolute zero or an interval of 100 °C between the solidification and boiling points of water. If we fix the interval and repeat the measurements to extrapolate to absolute zero, we get -273.22 °C.

In 1954, the CIPM adopted a resolution on the transition to a new definition of Kelvin, which had nothing to do with the interval 0 -100 °C. It actually assigned the value of 273.16 K (0.01 °C) to the triple point of water and “let the boiling point of water float freely” at about 100 °C. Instead of "degree Kelvin" for the unit of temperature, simply "kelvin" was introduced.

From formula (3) it follows that by assigning a fixed value of 273.16 K to T in such a stable and well-reproducible state of the system as the triple point of water, the value of the constant k can be determined experimentally. Until recently, the most accurate experimental values ​​of the Boltzmann constant k were obtained by the extremely rarefied gas method.

There are other methods for obtaining the Boltzmann constant, based on the use of laws that include the parameter kT.

This is the Stefan-Boltzmann law, according to which the total energy of thermal radiation E(T) is a fourth power function of CT.
Equation relating the square of the speed of sound in an ideal gas to 0 2 linear dependence with CT.
Equation for the mean square noise voltage on the electrical resistance V 2, also linearly dependent on CT.

Installations for implementing the above determination methods CT are called absolute thermometry or primary thermometry instruments.

Thus, there are many conventions in determining temperature values ​​in kelvins rather than joules. The main thing is that the proportionality coefficient itself k between temperature and energy units is not constant. It depends on the accuracy of thermodynamic measurements currently achievable. This approach is not very convenient for primary thermometers, especially those operating in a temperature range far from the triple point. Their readings will depend on changes in the value of Boltzmann's constant.

Every change in the practical international temperature scale is the result of scientific research by metrological centers around the world. The introduction of a new edition of the temperature scale affects the calibration of all temperature measuring instruments.

Every person encounters the concept of temperature every day. The term has firmly entered our daily life: we heat food in a microwave oven or cook food in the oven, we are interested in the weather outside or find out whether the water in the river is cold - all this is closely related to this concept. What is temperature, what does this physical parameter mean, how is it measured? We will answer these and other questions in the article.

Physical quantity

Let's look at what temperature is from the point of view of an isolated system in thermodynamic equilibrium. The term comes from Latin and means “proper mixture”, “normal state”, “proportionality”. This quantity characterizes the state of thermodynamic equilibrium of any macroscopic system. In the case when it is out of equilibrium, over time there is a transition of energy from more heated objects to less heated ones. The result is equalization (change) of temperature throughout the system. This is the first postulate (zero law) of thermodynamics.

Temperature determines the distribution of the constituent particles of the system by energy levels and speeds, the degree of ionization of substances, the properties of equilibrium electromagnetic radiation of bodies, and the total volumetric radiation density. Since for a system that is in thermodynamic equilibrium, the listed parameters are equal, they are usually called the temperature of the system.

Plasma

In addition to equilibrium bodies, there are systems in which the state is characterized by several temperature values ​​that are not equal to each other. A good example is plasma. It consists of electrons (light charged particles) and ions (heavy charged particles). When they collide, a rapid transfer of energy occurs from electron to electron and from ion to ion. But between heterogeneous elements there is a slow transition. Plasma can be in a state in which electrons and ions individually are close to equilibrium. In this case, it is possible to assume separate temperatures for each type of particle. However, these parameters will differ from each other.

Magnets

In bodies in which particles have a magnetic moment, energy transfer usually occurs slowly: from translational to magnetic degrees of freedom, which are associated with the possibility of changing the directions of the moment. It turns out that there are states in which the body is characterized by a temperature that does not coincide with the kinetic parameter. It corresponds to the forward motion of elementary particles. Magnetic temperature determines part of the internal energy. It can be both positive and negative. During the equalization process, energy will be transferred from particles with a higher temperature to particles with a lower temperature if they are both positive or negative. In the opposite situation, this process will proceed in the opposite direction - the negative temperature will be “higher” than the positive one.

Why is this necessary?

The paradox is that the average person, in order to carry out the measurement process both in everyday life and in industry, does not even need to know what temperature is. It will be enough for him to understand that this is the degree of heating of an object or environment, especially since we have been familiar with these terms since childhood. Indeed, most practical instruments designed to measure this parameter actually measure other properties of substances that change depending on the level of heating or cooling. For example, pressure, electrical resistance, volume, etc. Further, such readings are manually or automatically recalculated to the required value.

It turns out that to determine the temperature, there is no need to study physics. Most of the population of our planet lives by this principle. If the TV is working, then there is no need to understand the transient processes of semiconductor devices, study the socket or how the signal is received. People are accustomed to the fact that in every area there are specialists who can repair or debug the system. The average person does not want to strain his brain, because it is much better to watch a soap opera or football on the “box” while sipping a cold beer.

And I want to know

But there are people, most often these are students, who, either out of curiosity or out of necessity, are forced to study physics and determine what temperature really is. As a result, in their search they find themselves in the jungle of thermodynamics and study its zeroth, first and second laws. In addition, an inquisitive mind will have to comprehend entropy. And at the end of his journey, he will probably admit that defining temperature as a parameter of a reversible thermal system, which does not depend on the type of working substance, will not add clarity to the sense of this concept. And all the same, the visible part will be some degrees accepted by the international system of units (SI).

Temperature as kinetic energy

A more “tangible” approach is called the molecular kinetic theory. From it, the idea is formed that heat is considered as a form of energy. For example, the kinetic energy of molecules and atoms, a parameter averaged over a huge number of chaotically moving particles, turns out to be a measure of what is commonly called the temperature of a body. Thus, particles in a heated system move faster than in a cold system.

Since the term in question is closely related to the averaged kinetic energy of a group of particles, it would be quite natural to use the joule as a unit of temperature measurement. However, this does not happen, which is explained by the fact that the energy of thermal motion of elementary particles is very small in relation to the joule. Therefore, it is inconvenient to use. Thermal motion is measured in units derived from joules using a special conversion factor.

Temperature units

Today, three main units are used to display this parameter. In our country, temperature is usually determined in degrees Celsius. This unit of measurement is based on the solidification point of water - the absolute value. It is the starting point. That is, the temperature of the water at which ice begins to form is zero. In this case, water serves as an exemplary yardstick. This convention has been adopted for convenience. The second absolute value is the vapor temperature, that is, the moment when water changes from a liquid state to a gaseous state.

The next unit is degrees Kelvin. The origin of this system is considered to be the point So, one degree Kelvin is equal to one. The only difference is the origin. We find that zero Kelvin will be equal to minus 273.16 degrees Celsius. In 1954, the General Conference on Weights and Measures decided to replace the term "kelvin" for the unit of temperature with "kelvin".

The third commonly accepted unit of measurement is degrees Fahrenheit. Until 1960, they were widely used in all English-speaking countries. However, this unit is still used in everyday life in the United States. The system is fundamentally different from those described above. The freezing point of a mixture of salt, ammonia and water in a 1:1:1 ratio is taken as the starting point. So, on the Fahrenheit scale, the freezing point of water is plus 32 degrees, and the boiling point is plus 212 degrees. In this system, one degree is equal to 1/180 of the difference between these temperatures. Thus, the range from 0 to +100 degrees Fahrenheit corresponds to the range from -18 to +38 Celsius.

Absolute zero temperature

Let's figure out what this parameter means. Absolute zero is the value of the limiting temperature at which the pressure of an ideal gas becomes zero for a fixed volume. This is the lowest value in nature. As Mikhailo Lomonosov predicted, “this is the greatest or last degree of cold.” From this it follows that equal volumes of gases, subject to the same temperature and pressure, contain the same number of molecules. What follows from this? There is a minimum temperature of a gas at which its pressure or volume goes to zero. This absolute value corresponds to zero Kelvin, or 273 degrees Celsius.

Some interesting facts about the solar system

The temperature on the surface of the Sun reaches 5700 Kelvin, and in the center of the core - 15 million Kelvin. The planets of the solar system differ greatly from each other in terms of heating levels. Thus, the temperature of the core of our Earth is approximately the same as on the surface of the Sun. Jupiter is considered the hottest planet. The temperature at the center of its core is five times higher than at the surface of the Sun. But the lowest value of the parameter was recorded on the surface of the Moon - it was only 30 Kelvin. This value is even lower than on the surface of Pluto.

Facts about Earth

1. The highest temperature recorded by man was 4 billion degrees Celsius. This value is 250 times higher than the temperature of the Sun's core. The record was set by the New York Brookhaven Natural Laboratory in an ion collider, the length of which is about 4 kilometers.

2. The temperature on our planet is also not always ideal and comfortable. For example, in the city of Verkhnoyansk in Yakutia, the temperature in winter drops to minus 45 degrees Celsius. But in the Ethiopian city of Dallol the situation is the opposite. There the average annual temperature is plus 34 degrees.

3. The most extreme conditions under which people work are recorded in gold mines in South Africa. Miners work at a depth of three kilometers at a temperature of plus 65 degrees Celsius.

Thermodynamic definition

History of the thermodynamic approach

The word “temperature” arose in those days when people believed that more heated bodies contained a larger amount of a special substance - caloric, than less heated ones. Therefore, temperature was perceived as the strength of a mixture of body matter and caloric. For this reason, the units of measurement for the strength of alcoholic beverages and temperature are called the same - degrees.

Determination of temperature in statistical physics

Temperature measuring instruments are often calibrated on relative scales - Celsius or Fahrenheit.

In practice, temperature is also measured

The most accurate practical thermometer is the platinum resistance thermometer. The latest methods for measuring temperature have been developed, based on measuring the parameters of laser radiation.

Temperature units and scale

Since temperature is the kinetic energy of molecules, it is clear that it is most natural to measure it in energy units (that is, 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.

Absolute temperature. Kelvin temperature scale

The concept of absolute temperature was introduced by W. Thomson (Kelvin), and therefore the absolute temperature scale is called the Kelvin scale or thermodynamic temperature scale. The unit of absolute temperature is kelvin (K).

The absolute temperature scale is so called because the measure of the ground state of the lower limit of temperature is absolute zero, that is, the lowest possible temperature at which, in principle, it is impossible to extract thermal energy from a substance.

Absolute zero is defined as 0 K, which is equal to −273.15 °C.

The Kelvin temperature scale is a scale that starts at absolute zero.

Of great importance is the development, based on the Kelvin thermodynamic scale, of International practical scales based on reference points - phase transitions of pure substances determined by primary thermometry methods. The first international temperature scale was adopted in 1927 by ITS-27. Since 1927, the scale has been redefined several times (MTSh-48, MPTS-68, MTSh-90): reference temperatures and interpolation methods have changed, but the principle remains the same - the basis of the scale is a set of phase transitions of pure substances with certain values ​​of thermodynamic temperatures and interpolation instruments calibrated at these points. The ITS-90 scale is currently in effect. The main document (Regulations on the scale) establishes the definition of Kelvin, the values ​​of phase transition temperatures (reference points) and interpolation methods.

Temperature scales used in everyday life - both Celsius and Fahrenheit (used mainly in the USA) - are not absolute and therefore inconvenient when conducting experiments in conditions where the temperature drops below the freezing point of water, which is why the temperature has to be expressed negative number. For such cases, absolute temperature scales were introduced.

One of them is called the Rankine scale, and the other is the absolute thermodynamic scale (Kelvin scale); their temperatures are measured in degrees Rankine (°Ra) and kelvins (K), respectively. Both scales begin at absolute zero temperature. They differ in that the price of one division on the Kelvin scale is equal to the price of a division on the Celsius scale, and the price of one division on the Rankine scale is equivalent to the price of division of thermometers with the Fahrenheit scale. The freezing point of water at standard atmospheric pressure corresponds to 273.15 K, 0 °C, 32 °F.

The Kelvin scale is tied to the triple point of water (273.16 K), and the Boltzmann constant depends on it. This creates problems with the accuracy of interpretation of high temperature measurements. The BIPM is now considering the possibility of moving to a new definition of Kelvin and fixing the Boltzmann constant, instead of reference to the triple point temperature. .

Celsius

In technology, medicine, meteorology and in everyday life, the Celsius scale is used, in which the temperature of the triple point of water is 0.008 °C, and, therefore, the freezing point of water at a pressure of 1 atm is 0 °C. Currently, the Celsius scale is determined through the Kelvin scale: the price of one division on the Celsius scale is equal to the price of a division on the Kelvin scale, t(°C) = T(K) - 273.15. Thus, the boiling point of water, originally chosen by Celsius as a reference point of 100 °C, has lost its significance, and modern estimates put the boiling point of water at normal atmospheric pressure at about 99.975 °C. The Celsius scale is practically very convenient, since water is very widespread on our planet and our life is based on it. Zero Celsius is a special point for meteorology because it is associated with the freezing of atmospheric water. The scale was proposed by Anders Celsius in 1742.

Fahrenheit

In England and especially in the USA, the Fahrenheit scale is used. Zero degrees Celsius is 32 degrees Fahrenheit, and 100 degrees Celsius is 212 degrees Fahrenheit.

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

Reaumur scale

Transitions from different scales

Comparison of temperature scales

¹ The normal average human body temperature is 36.6 °C ±0.7 °C, or 98.2 °F ±1.3 °F. The commonly quoted value of 98.6°F is an exact conversion to Fahrenheit of the 19th century German value of 37°C. However, this value is not within the range of normal average human body temperature, since the temperature of different parts of the body is different.

Some values ​​in this table are rounded.

Characteristics of phase transitions

To describe the phase transition points of various substances, the following temperature values ​​are used:

• Annealing temperature
• Sintering temperature
• Synthesis temperature
• Air temperature
• Soil temperature
• Homologous temperature
• Debye temperature (Characteristic temperature)

See also

Notes

Literature