The question “What is a temperature scale?” - suitable for any physicist - from student to professor. A complete answer to this question would fill a whole book, and would serve as a good illustration of the changing views and progress of the physicist during the last four centuries.
Temperature is the degree of heating on a certain scale. You can use the sensitivity of your own skin to make a rough estimate without a thermometer, but our senses of heat and cold are limited and unreliable.

Experience. Skin sensitivity to heat and cold. This experience is very instructive. Place three bowls of water: one with very hot water, one with moderately warm water, and the third with very cold water. Place one hand in a hot basin and the other in a cold basin for 3 minutes. Then place both hands in a basin of warm water. Now ask each hand, what will it “tell” you about the temperature of the water?

The thermometer tells us exactly how much hotter or colder a thing is; it can be used to compare the degree of heating various items, using it again and again, we can compare observations made in different time. It is equipped with a certain constant, reproducible scale - a characteristic feature of any good instrument. The method of making a thermometer and the device itself dictate to us the scale and measurement system that we must use. The transition from rough sensations to an instrument with a scale is not just an improvement in our knitting. We invent and introduce a new concept - temperature.
Our crude idea of ​​hot and cold contains in embryo the concept of temperature. Research shows that when heated, many of the the most important properties things change, etc. thermometers are needed to study these changes. The widespread use of thermometers in everyday life has relegated the meaning of the concept of temperature to the background. We think that a thermometer measures the temperature of our body, air or bath water, although in fact it only shows its own temperature. We consider temperature changes from 60 to 70° and from 40 to 50° to be the same. However, we apparently have no guarantee that they are really the same. We can only consider them the same by definition. Thermometers are still useful to us as faithful servants. But is Her Ladyship the Temperature really hidden behind their devoted “face” - the scale?

Simple thermometers and the Celsius scale
The temperature in thermometers is shown by a drop of liquid (mercury or colored alcohol) expanding when heated, placed in a tube with divisions. In order for the scale of one thermometer to coincide with another, we take two points: the melting of ice and the boiling of water under standard conditions and assign divisions of 0 and 100 to them, and divide the interval between them by 100 equal parts. So, if according to one thermometer the temperature of the water in the bath is 30°, then any other thermometer (if it is correctly calibrated) will show the same, even if it has a bubble and a tube of a completely different size. In the first thermometer, mercury expands by 30/100 the expansion from its melting point to its boiling point. It is reasonable to expect that in other thermometers the mercury will expand to the same extent and they will also show 30°. Here we rely on the Universality of Nature 2>.
Suppose now that we take another liquid, for example glycerin. Will this give the same scale at the same points? Of course, to harmonize with mercury, a glycerin thermometer must have 0° when ice melts and 100° when water boils. But will the thermometer readings be the same at intermediate temperatures? It turns out that when a mercury thermometer shows 50.0° C, a glycerin thermometer shows 47.6° C. Compared to a mercury thermometer, the glycerin thermometer lags a little behind in the first half of the way between the melting point of ice and the boiling point of water. (You can make thermometers that will give an even greater discrepancy. For example, a thermometer with water vapor would show 12° at a point where the mercury is 50°!

This produces the so-called Celsius scale, which is widely used today. In the USA, England and some other countries, the Fahrenheit scale is used, on which the melting points of ice and boiling water are marked with the numbers 32 and 212. Initially, the Fahrenheit scale was based on two other points. The temperature of the freezing mixture was taken as zero, and the number 96 (a number that splits into big number factors and therefore easy to handle) was compared to the normal temperature of the human body. After modification, when whole numbers were assigned to the standard points, the body temperature was between 98 and 99. A room temperature of 68° R corresponds to 20° C. Although the transition from one scale to another changes the numerical value of the temperature unit, it does not affect the concept itself temperature. The latest international agreement introduced another change: instead of the standard melting points of ice and boiling water defining the scale, the adoption of “absolute zero” and “triple point” for water was adopted. Although this change in the definition of temperature is fundamental, in the usual scientific work it makes virtually no difference. For the triple point, the number is chosen so that the new scale agrees very well with the old one.
2> This reasoning is somewhat naive. Glass also expands. Does the expansion of glass affect the height of the mercury column? For this reason, other than the simple expansion of mercury, what does the thermometer show? Let's say that two thermometers contain pure mercury, but their balls are made of different types of glass with different expansions. Will this affect the result?

If mechanics in the 18th century became a mature, well-defined field of natural science, then the science of heat essentially took only its first steps. Of course, a new approach to the study of thermal phenomena emerged back in the 17th century. Galileo's thermoscope and the subsequent thermometers of the Florentine academicians, Guericke, and Newton prepared the ground on which thermometry grew already in the first quarter of the new century. Thermometers of Fahrenheit, Delisle, Lomonosov, Reaumur and Celsius, differing from each other in design features, at the same time determined the type of thermometer with two constant points, which is still accepted today.

Back in 1703, the Parisian academician Amonton (1663-1705) designed a gas thermometer in which the temperature was determined using a manometric tube connected to a gas reservoir of constant volume. A theoretically interesting device, a prototype of modern hydrogen thermometers, was inconvenient for practical purposes. The Danzig (Gdansk) glassblower Fahrenheit (1686-1736) had been producing alcohol thermometers with constant points since 1709. In 1714 he began producing mercury thermometers. Fahrenheit took the freezing point of water as 32°, the boiling point of water as 212°. Fahrenheit was considered to be the freezing point of a mixture of water, ice and ammonia or table salt. He named the boiling point of water only in 1724 in a printed publication. Whether he used it before is unknown.

The French zoologist and metallurgist Reaumur (1683-1757) proposed a thermometer with a constant zero point, for which he took the freezing point of water. Using an 80% alcohol solution as a thermometric body, and in the final version mercury, he took the boiling point of water as the second constant point, designating it as the number 80. Reaumur described his thermometer in articles published in the journal of the Paris Academy of Sciences in 1730, 1731 gg.

The test of Reaumur's thermometer was carried out by the Swedish astronomer Celsius (1701-1744), who described his experiments in 1742. “These experiments,” he wrote, “I repeated for two years, in all the winter months, under different weather and various changes in the state of the barometer, and always found exactly the same point on the thermometer. I not only placed the thermometer in melting ice, but also, in extreme cold, brought snow into my room on the fire until it began to melt. I also placed a cauldron with melting snow together with a thermometer in a heating stove and always found that the thermometer showed the same point, if only the snow lay tightly around the thermometer ball. After carefully checking the constancy of the melting point of ice, Celsius examined the boiling point of water and found that it depended on pressure. As a result of the research, a new thermometer appeared, now known as the Celsius thermometer. Celsius took the melting point of ice as 100, the boiling point of water at a pressure of 25 inches 3 lines of mercury as 0. The famous Swedish botanist Carl Linnaeus (1707-1788) used a thermometer with rearranged values ​​of constant points. O meant the melting point of ice, 100 meant the boiling point of water. Thus, the modern Celsius scale is essentially the Linnaean scale.

IN St. Petersburg Academy Sciences, Academician Delisle proposed a scale in which the melting point of ice was taken as 150, and the boiling point of water as 0. Academician P. S. Pallas in his expeditions of 1768-1774. in the Urals and Siberia I used the Deli thermometer. M.V. Lomonosov used in his research a thermometer he designed with a scale inverse to the Deli scale.

Thermometers were used primarily for meteorological and geophysical purposes. Lomonosov, who discovered the existence of vertical currents in the atmosphere, studying the dependence of the density of atmospheric layers on temperature, provides data from which it is possible to determine the coefficient of volumetric expansion of air, which, according to these data, is approximately ]/367. Lomonosov passionately defended the priority of the St. Petersburg academician Brown in the discovery of the freezing point of mercury, who on December 14, 1759 first froze mercury using cooling mixtures. This was the lowest temperature reached at that time.

The highest temperatures (without quantitative estimates) were obtained in 1772 by a commission of the Paris Academy of Sciences under the leadership of the famous chemist Lavoisier. High temperatures were obtained using a specially made lens. The lens was assembled from two concave-convex lentils, the space between which was filled with alcohol. About 130 liters of alcohol were poured into a lens with a diameter of 120 cm; its thickness reached 16 cm in the center. By focusing the sun's rays, it was possible to melt zinc, gold, and burn diamond. Both in the experiments of Brown-Lomonosov, where the “refrigerator” was winter air, and in the experiments of Lavoisier, the source of high temperatures was the natural “stove” - the Sun.

The development of thermometry was the first scientific and practical use of the thermal expansion of bodies. Naturally, the phenomenon of thermal expansion itself began to be studied not only qualitatively, but also quantitatively. The first accurate measurements of thermal expansion solids were carried out by Lavoisier and Laplace in 1782. Their method for a long time was described in physics courses, starting with Biot’s course, 1819, and ending with O. D. Khvolson’s physics course, 1923.

A strip of the body being tested was placed first in melting ice and then in boiling water. Data were obtained for various types of glass, steel and iron, as well as for different types of gold, copper, brass, silver, tin, lead. Scientists have found that depending on the method of preparing the metal, the results are different. A strip of unhardened steel increases by 0.001079 of its original length when heated by 100°, and a strip of hardened steel increases by 0.001239. For wrought iron a value of 0.001220 was obtained, for round drawn iron it was 0.001235. These data give an idea of ​​the accuracy of the method.

So, already in the first half of the 18th century, thermometers were created and quantitative thermal measurements, brought to high degree accuracy in the thermophysical experiments of Laplace and Lavoisier. However, the basic quantitative concepts of thermophysics did not crystallize immediately. In the works of physicists of that time, there was considerable confusion in such concepts as “amount of heat”, “degree of heat”, “degree of heat”. The need to distinguish between the concepts of temperature and amount of heat was pointed out in 1755 by I. G. Lambert (1728-1777). However, his instructions were not appreciated by his contemporaries, and the development of correct concepts was slow.

The first approaches to calorimetry are contained in the works of St. Petersburg academicians G.V. Kraft and G.V. Richman (1711-1753). Kraft's paper "Different Experiments with Heat and Cold," presented to the Academy Conference in 1744 and published in 1751, deals with the problem of determining the temperature of a mixture of two portions of liquid taken at different temperatures. This problem was often called “Richmann’s problem” in textbooks, although Richmann solved a more general and more complex problem than Kraft. Kraft gave an incorrect empirical formula to solve the problem.

We find a completely different approach to solving the problem in Richman. In the article “Reflections on the amount of heat that should be obtained by mixing liquids having certain degrees of heat,” published in 1750, Richmann poses the problem of determining the temperature of a mixture of several (and not two, as in Kraft) liquids and solves it based on the principle of heat balance. “Suppose,” says Richman, “that the mass of the liquid is equal to a; the heat distributed in this mass is equal to m; let the other mass, in which the same heat m be distributed as in mass a, be equal to a + b. Then the resulting heat

is equal to am/(a+b). Here Richmann understands temperature by “heat,” but the principle he formulated that “the same heat is inversely proportional to the masses over which it is distributed” is purely calorimetric. “Thus,” writes Richmann further, “the heat of mass a, equal to m, and the heat of mass b, equal to n, are uniformly distributed over mass a + b, and the heat in this mass, i.e., in a mixture of a and b, must be equal to the sum of heats m + n distributed in the mass a + b, or equal to (ma + nb) / (a ​​+ b) . This formula appeared in textbooks as the “Richmann formula”. “In order to obtain a more general formula,” continues Richman, “by which it would be possible to determine the degree of heat when mixing 3, 4, 5, etc. masses of the same liquid, having different degrees of heat, I called these masses a, b, c, d, e, etc., and the corresponding heats are m, n, o, p, q, etc. In exactly the same way I assumed that each of them is distributed over the totality of all masses.” As a result, “the heat after mixing all the warm masses is equal to:

(am + bп + с + dp + eq) etc./(a + b + c+d + e) ​​etc.

that is, the sum of liquid masses, over which the heat of individual masses is evenly distributed when mixed, is related to the sum of all products of each mass by its heat in the same way as unity is to the heat of the mixture.”

Richmann did not yet master the concept of the amount of heat, but he wrote and logically substantiated a completely correct calorimetric formula. He easily discovered that his formula agreed better with experience than Krafg’s formula. He correctly established that his “heats” were “not actual heat, but the excess heat of the mixture compared to zero degrees Fahrenheit.” He clearly understood that: 1. “The heat of the mixture is distributed not only throughout its mass itself, but also along the walls of the vessel and the thermometer itself.” 2. “The thermometer’s own heat and the heat of the vessel are distributed throughout the mixture, along the walls of the vessel in which the mixture is located, and throughout the thermometer.” 3. “Part of the heat of the mixture, during the period of time while the experiment is being carried out, passes into the surrounding air...”

Richman accurately formulated the sources of errors in calorimetric experiments, indicated the reasons for the discrepancy between Kraft's formula and experiment, i.e., he laid the foundations of calorimetry, although he himself had not yet approached the concept of the amount of heat. Richmann's work was continued by the Swedish academician Johann Wilcke (1732-1796) and the Scottish chemist Joseph Black (1728-1799). Both scientists, relying on Richmann’s formula, found it necessary to introduce new concepts into science. Wilke, while studying the heat of a mixture of water and snow in 1772, discovered that part of the heat disappears. Hence, he came to the concept of latent heat of snow melting and the need to introduce a new concept, which was later called “heat capacity.”

Black, who did not publish his results, came to the same conclusion. His research was published only in 1803, and then it became known that Black was the first to clearly distinguish between the concepts of quantity of heat and temperature, and the first to introduce the term “heat capacity.” Back in 1754-1755, Black discovered not only the constancy of the melting point of ice, but also that the thermometer remains at the same temperature, despite the influx of heat, until all the ice has melted. From here Black came to the concept of latent heat of fusion. Later he established the concept of latent heat of vaporization. Thus, by the 70s of the 18th century, the basic calorimetric concepts were established. Only almost a hundred years later (in 1852) was the unit of heat quantity introduced, which much later received the name “calorie.”( Clausius also speaks simply about the unit of heat and does not use the term “calorie”.)

In 1777, Lavoisier and Laplace, having built an ice calorimeter, determined the specific heat capacities of various bodies. Aristotle's primary quality, heat, began to be studied by precise experiment.

Scientific theories of heat also appeared. One, the most common concept (Black also adhered to it) is the theory of a special thermal fluid - caloric. The other, of which Lomonosov was a zealous supporter, considered heat as a type of movement of “insensitive particles.” The concept of caloric was very well suited to the description of calorimetric facts: Richmann's formula and later formulas taking into account latent heat could be perfectly explained. As a result, the theory of caloric dominated until the middle of the 19th century, when the discovery of the law of conservation of energy forced physicists to return to the concept successfully developed by Lomonosov another hundred years before the discovery of this law.

The idea that heat is a form of motion was very common in the 17th century. f. Bacon in the New Organon, applying his method to the study of the nature of heat, comes to the conclusion that “heat is a movement of propagation, hindered and occurring in small parts.” Descartes speaks more specifically and clearly about heat as the movement of small particles. Considering the nature of fire, he comes to the conclusion that “the body of the flame... is composed of tiny particles, moving very quickly and violently separately from one another.” He further points out that “only this movement, depending on the various actions it produces, is called either heat or light.” Moving on to the rest of the bodies, he states “that small particles that do not stop their movement are present not only in fire, but also in all other bodies, although in the latter their action is not so strong, and due to their small size they themselves cannot to be noticed by any of our senses."

Atomism dominated the physical views of scientists and thinkers of the 17th century. Hooke, Huygens, Newton imagined all the bodies of the Universe as consisting of tiny particles, “insensitive”, as Lomonosov later briefly called them. The concept of heat as a form of movement of these particles seemed quite reasonable to scientists. But these ideas about heat were qualitative in nature and arose on a very meager factual basis. In the 18th century knowledge about thermal phenomena became more accurate and definite; chemistry also made great strides, in which the theory of phlogiston, before the discovery of oxygen, helped to understand the processes of combustion and oxidation. All this contributed to the assimilation of a new point of view on heat as a special substance, and the first successes of calorimetry strengthened the position of supporters of caloric. It took great scientific courage to develop the kinetic theory of heat in this situation.

The kinetic theory of heat was naturally combined with the kinetic theory of matter, and above all air and vapor. Gases (the word “gas” was introduced by Van Helmont; 1577-1644) essentially had not yet been discovered, and even Lavoisier considered steam as a combination of water and fire. Lomonosov himself, observing the dissolution of iron in strong vodka (nitric acid), believed

nitrogen bubbles released by air. Thus, air and steam were almost the only gases in Lomonosov’s time - “elastic liquids”, according to the terminology of that time.

D. Bernoulli in his “Hydrodynamics” imagined air as consisting of particles moving “extremely quickly in various directions”, and believed that these particles form an “elastic fluid”. Bernoulli substantiated the Boyle-Mariotte law with his model of “elastic fluid”. He established a connection between the speed of particle movement and the heating of air and thereby explained the increase in air elasticity when heated. This was the first attempt in the history of physics to interpret the behavior of gases by the movement of molecules, an undoubtedly brilliant attempt, and Bernoulli went down in the history of physics as one of the founders kinetic theory gases

Six years after the publication of Hydrodynamics, Lomonosov presented his work “Reflections on the Cause of Heat and Cold” to the Academic Assembly. It was published only six years later, in 1750, together with another, later work, “An Experience in the Theory of Air Elasticity.” Thus, Lomonosov's theory of elasticity of gases is inextricably linked with his theory of heat and is based on the latter.

D. Bernoulli also paid great attention to issues of heat, in particular the issue of the dependence of air density on temperature. Not limiting himself to referring to Amonton's experiments, he himself tried to experimentally determine the dependence of air elasticity on temperature. “I found,” writes Bernoulli, “that the elasticity of the air, which was very cold here in St. Petersburg on December 25, 1731 Art. Art., refers to the elasticity of the same air, which has the same heat as boiling water, as 523 to 1000.” This value from Bernoulli is clearly incorrect, since it assumes that the cold air temperature corresponds to - 78 ° C.

Lomonosov’s similar calculations, mentioned above, are much more accurate. But the final result of Bernoulli is very remarkable: “the elasticities are in the ratio composed of the square of the particle velocities and the first power of densities,” which is entirely consistent with the basic equation of the kinetic theory of gases in the modern presentation.

Bernoulli did not touch at all on the question of the nature of heat, which was central to Lomonosov’s theory. Lomonosov hypothesizes that heat is a form of motion of insensitive particles. He considers the possible nature of these movements: translational motion, rotational and oscillatory - and states that "heat consists in the internal rotational motion of bound matter."

Having accepted as an initial premise the hypothesis of the rotational motion of molecules as the cause of heat, Lomonosov deduces from this a number of consequences: 1) molecules (corpuscles) have a spherical shape; 2) “...with faster rotation of particles of bound matter, heat should increase, and with slower rotation, it should decrease; 3) particles of hot bodies rotate faster, particles of cold bodies rotate slower; 4) hot bodies must cool when in contact with cold ones, since it slows down the calorific movement of particles; on the contrary, cold bodies must heat up due to the acceleration of movement upon contact.” Thus, the transition of heat from a hot body to a cold one observed in nature is a confirmation of Lomonosov’s hypothesis.

The fact that Lomonosov singled out heat transfer as one of the main consequences is very significant, and some authors see this as a basis for classifying Lomonosov as the discoverer of the second law of thermodynamics. It is unlikely, however, that the above statement can be considered as the primary formulation of the second law, but the entire work as a whole is undoubtedly the first sketch of thermodynamics. Thus, Lomonosov explains in it the formation of heat during friction, which served experimental basis the first principle in Joule's classical experiments. Lomonosov further, touching on the issue of the transition of heat from a hot body to a cold one, refers to the following position: “Body A, acting on body B, cannot give the latter a greater speed of movement than what it itself has.” This position is a specific case of the “universal law of conservation”. Based on this position, he proves that a cold body B, immersed in a warm liquid A, “obviously cannot perceive a greater degree of heat than that of A.”

Lomonosov postpones the question of thermal expansion “until another time,” until he considers the elasticity of air. His thermodynamic work is thus directly adjacent to his later work on the elasticity of gases. However, speaking of his intention to postpone consideration of thermal expansion “until another time,” Lomonosov also points out that since upper limit If there is no particle speed (the theory of relativity does not exist yet!), then there is no upper limit on temperature. But “of necessity there must be a greatest and final degree of cold, which must consist in the complete cessation of the rotational motion of the particles.” Lomonosov, therefore, asserts the existence of the “last degree of cold” - absolute zero.

In conclusion, Lomonosov criticizes the theory of caloric, which he considers a relapse of the ancient idea of ​​​​elementary fire. Taking apart various phenomena, both physical and chemical, associated with the release and absorption of heat, Lomonosov concludes that “the heat of bodies cannot be attributed to the condensation of some thin, specially intended matter, but that heat consists in the internal rotational movement of the connected matter of the heated body.” By “bound” matter, Lomonosov understands the matter of particles of bodies, distinguishing it from “flowing” matter, which can flow “like a river” through the pores of a body.

At the same time, Lomonosov included the world ether in his thermodynamic system, far ahead of not only his time, but also the 19th century. “Thereby,” Lomonosov continues, “we not only say that such movement and heat are also characteristic of that subtlest matter of the ether, which fills all spaces that do not contain sensitive bodies, but we also assert that the matter of the ether can impart the calorific motion received from the sun our earth and the rest of the bodies of the world and heat them, being the medium through which bodies distant from each other impart heat without the mediation of anything tangible.”

So, Lomonosov, long before Boltzmann, Golitsyn and Wien, included thermal radiation in thermodynamics. Lomonosov's thermodynamics is a remarkable achievement of scientific thought of the 18th century, far ahead of its time.

The question arises: why did Lomonosov refuse to consider the thermal translational motion of particles, but settled on rotational motion? This assumption greatly weakened his work, and D. Bernoulli's theory came much closer to the later studies of Clausius and Maxwell than Lomonosov's theory. Lomonosov had very deep thoughts on this matter. He had to explain such contradictory things as cohesion and elasticity, the coherence of body particles and the ability of bodies to expand. Lomonosov was an ardent opponent of long-range forces and could not resort to them when considering molecular structure tel. He also did not want to reduce the explanation of the elasticity of gases to elastic impacts of particles, that is, to explain elasticity by elasticity. He was looking for a mechanism that would explain both elasticity and thermal expansion in the most natural way. In his work “An Experience in the Theory of Air Elasticity,” he rejects the hypothesis of the elasticity of the particles themselves, which, according to Lomonosov, “are devoid of any physical composition and organized structure...” and are atoms. Therefore, the property of elasticity is not exhibited by individual particles that do not have any physical complexity and organized structure, but is produced by a collection of them. So, the elasticity of gas (air), according to Lomonosov, is “a property of a collective of atoms.” The atoms themselves, according to Lomonosov, “must be solid and have extension,” and he considers their shape “very close” to spherical. The phenomenon of heat arising from friction forces him to accept the hypothesis that “air atoms are rough.” The fact that the elasticity of air is proportional to density leads Lomonosov to conclude “that it comes from some direct interaction of its atoms.” But atoms, according to Lomonosov, cannot act at a distance, but act only upon contact. The compressibility of air proves the presence of empty spaces in it, which make it impossible for atoms to interact. From here Lomonosov comes to a dynamic picture, when the interaction of atoms is replaced in time by the formation of empty space between them, and the spatial separation of atoms is replaced by contact. “It is evident, then, that the individual atoms of the air, in disorderly alternation, collide with the nearest ones at insensitive intervals of time, and when some are in contact, others rebound from each other and collide with those closest to them, in order to rebound again; Thus, continually pushed away from each other by frequent mutual shocks, they tend to disperse in all directions.” Lomonosov sees elasticity in this scattering in all directions. “The force of elasticity consists in the tendency of air to spread in all directions.”

It is, however, necessary to explain why atoms bounce off each other when interacting. The reason for this, according to Lomonosov, is thermal movement: “The interaction of air atoms is due only to heat.” And since heat consists in the rotational motion of particles, to explain their repulsion it is enough to consider what happens when two rotating spherical rough particles come into contact. Lomonosov shows that they will push away from each other, and illustrates this with the example of the rebound of tops (“head over heels”) that boys throw on ice, well known to him from childhood. When such spinning tops come into contact, they bounce away from each other over considerable distances. Thus, elastic collisions of atoms, according to Lomonosov, are caused by the interaction of their rotational moments. That's why he needed the hypothesis of thermal rotational motion of particles! Thus, Lomonosov completely substantiated the model of an elastic gas consisting of chaotically moving and colliding particles.

This model allowed Lomonosov not only to explain the Boyle-Mariotte law, but also to predict deviations from it under large compressions. An explanation of the law and deviations from it was given by Lomonosov in his work “Addition to Reflections on the Elasticity of Air,” published in the same volume of “New Commentaries” of the St. Petersburg Academy of Sciences in which the two previous works were published. In Lomonosov's works there are also incorrect statements, which can be fully explained by the level of knowledge of that time. But they do not determine the significance of a scientist’s work. One cannot help but admire the courage and depth of Lomonosov’s scientific thought, who, in the infancy of the science of heat, created a powerful theoretical concept that was far ahead of its era. Contemporaries did not follow the path of Lomonosov; in the theory of heat, as was said, caloric reigned; the physical thinking of the 18th century required various substances: thermal, light, electrical, magnetic. Usually this is seen as the metaphysical nature of the thinking of natural scientists of the 18th century, and some of its reactionary nature. But why did it become like this? It seems that the reason for this lies in the progress of exact natural science. In the 18th century learned to measure heat, light, electricity, magnetism. Measures have been found for all these agents, just as they were found long ago for ordinary masses and volumes. This fact brought weightless agents closer to ordinary masses and liquids and forced them to be considered as an analogue of ordinary liquids. The concept of “weightless” was a necessary stage in the development of physics; it made it possible to penetrate deeper into the world of thermal, electrical and magnetic phenomena. She contributed to the development of accurate experimentation, the accumulation of numerous facts and their primary interpretation.

Temperature scales. There are several graduated temperature scales, and the freezing and boiling temperatures of water are usually taken as reference points. Now the most common scale in the world is the Celsius scale. In 1742, Swedish astronomer Anders Celsius proposed a 100-degree thermometer scale in which 0 degrees is the boiling point of water at normal atmospheric pressure and 100 degrees is the melting temperature of ice. The scale division is 1/100 of this difference. When thermometers began to be used, it turned out to be more convenient to swap 0 and 100 degrees. Perhaps Carl Linnaeus participated in this (he taught medicine and natural science at the same Uppsala University where Celsius taught astronomy) who back in 1838 proposed taking the melting temperature of ice as 0 temperature, but it seems he did not think of a second reference point. By now, the Celsius scale has changed somewhat: 0°C is still taken to be the melting temperature of ice at normal pressure, which is not very dependent on pressure. But the boiling point of water at atmospheric pressure is now 99,975°C, which does not affect the measurement accuracy of almost all thermometers except special precision ones. The Fahrenheit temperature scales of Kelvin Reaumur and others are also known. The Fahrenheit temperature scale (in the second version adopted since 1714) has three fixed points: 0° corresponded to the temperature of a mixture of ice water and ammonia 96° - body temperature healthy person(under the arm or in the mouth). The reference temperature for comparing various thermometers was taken to be 32° for the melting point of the ice. The Fahrenheit scale is widespread in English-speaking countries, but it is almost never used in scientific literature. To convert Celsius temperature (°C) to Fahrenheit temperature (°F) there is a formula °F = (9/5)°C + 32 and for the reverse conversion there is a formula °C = (5/9)(°F-32) ). Both scales - both Fahrenheit and Celsius - are very inconvenient when conducting experiments in conditions where the temperature drops below the freezing point of water and is expressed negative number. For such cases, absolute temperature scales were introduced, which are based on extrapolation to the so-called absolute zero - the point at which molecular motion should stop. One of them is called the Rankine scale and the other is the absolute thermodynamic scale; temperatures are measured in degrees Rankine (°Ra) and kelvins (K). Both scales begin at absolute zero temperature and the freezing point of water corresponds to 491 7° R and 273 16 K. The number of degrees and kelvins between the freezing and boiling points of water on the Celsius scale and the absolute thermodynamic scale is the same and equal to 100; for the Fahrenheit and Rankine scales it is also the same but equal to 180. Celsius degrees are converted to kelvins using the formula K = °C + 273 16 and Fahrenheit degrees are converted to Rankine degrees using the formula °R = °F + 459 7. has been common in Europe for a long time Reaumur scale introduced in 1730 by Rene Antoine de Reaumur. It is not built arbitrarily like the Fahrenheit scale, but in accordance with the thermal expansion of alcohol (in a ratio of 1000:1080). 1 degree Reaumur is equal to 1/80 of the temperature interval between the points of melting ice (0°R) and boiling water (80°R) i.e. 1°R = 1.25°C 1°C = 0.8°R. but has now fallen into disuse.

On March 29, 1561, the Italian doctor Santorio was born - one of the inventors of the first mercury thermometer, a device that was an innovation for that time and which no person can do without today.

Santorio was not only a doctor, but also an anatomist and physiologist. He worked in Poland, Hungary and Croatia, actively studied the breathing process, “invisible evaporations” from the surface of the skin, and conducted research in the field of human metabolism. Santorio conducted experiments on himself and, studying the features human body, created many measuring instruments - a device for measuring the force of pulsation of arteries, scales for monitoring changes in a person’s mass, and the first mercury thermometer.

Three inventors

It is quite difficult to say today who exactly created the thermometer. The invention of the thermometer is attributed to many scientists at once - Galileo, Santorio, Lord Bacon, Robert Fludd, Scarpi, Cornelius Drebbel, Porte and Salomon de Caus. This is due to the fact that many scientists simultaneously worked on creating a device that would help measure the temperature of air, soil, water, and humans.

There is no description of this device in Galileo's own writings, but his students testified that in 1597 he created a thermoscope - an apparatus for raising water using heat. The thermoscope was a small glass ball with a glass tube soldered to it. The difference between a thermoscope and a modern thermometer is that in Galileo's invention, instead of mercury, air expanded. Also, it could only be used to judge the relative degree of heating or cooling of the body, since it did not yet have a scale.

Santorio from the University of Padua created his own device with which it was possible to measure the temperature of the human body, but the device was so bulky that it was installed in the courtyard of a house. Santorio's invention had the shape of a ball and an oblong winding tube on which divisions were drawn; the free end of the tube was filled with tinted liquid. His invention dates back to 1626.

In 1657, Florentine scientists improved the Galileo thermoscope, in particular by equipping the device with a bead scale.

Later, scientists tried to improve the device, but all thermometers were air, and their readings depended not only on changes in body temperature, but also on atmospheric pressure.

The first liquid thermometers were described in 1667, but they burst if the water froze, so they began to use wine alcohol to create them. The invention of a thermometer, the data of which would not be determined by changes in atmospheric pressure, occurred thanks to the experiments of the physicist Evangelista Torricelli, a student of Galileo. As a result, the thermometer was filled with mercury, turned upside down, colored alcohol was added to the ball, and the upper end of the tube was sealed.

Single scale and mercury

For a long time, scientists could not find starting points, the distance between which could be divided evenly.

The initial data for the scale were the thawing points of ice and melted butter, the boiling point of water, and some abstract concepts like “a significant degree of cold.”

Thermometer modern form, most suitable for everyday use, with an accurate measurement scale was created by the German physicist Gabriel Fahrenheit. He described his method for creating a thermometer in 1723. Initially, Fahrenheit created two alcohol thermometers, but then the physicist decided to use mercury in the thermometer. The Fahrenheit scale was based on three established points:

the first point was equal to zero degrees - this is the temperature of the composition of water, ice and ammonia;
the second, designated 32 degrees, is the temperature of the mixture of water and ice;
the third, the boiling point of water, was 212 degrees.
The scale was later named after its creator.

Reference
Today, the most common is the Celsius scale, the Fahrenheit scale is still used in the USA and England, and the Kelvin scale is used in scientific research.
But it was the Swedish astronomer, geologist and meteorologist Anders Celsius who finally established both constant points - melting ice and boiling water - in 1742. He divided the distance between points into 100 intervals, with the number 100 marking the melting point of ice, and 0 the boiling point of water.

Today, the Celsius scale is used inverted, that is, the melting point of ice is taken as 0°, and the boiling point of water as 100°.

According to one version, the scale was “turned over” by his contemporaries and compatriots, the botanist Carl Linnaeus and the astronomer Morten Stremer, after the death of Celsius, but according to another, Celsius himself turned over his scale on Stremer’s advice.

In 1848, the English physicist William Thomson (Lord Kelvin) proved the possibility of creating an absolute temperature scale, where the reference point is the value of absolute zero: -273.15 ° C - at this temperature further cooling of bodies is no longer possible.

Already in the middle of the 18th century, thermometers became an item of trade, and they were made by artisans, but thermometers came to medicine much later, in mid-19th century.

Modern thermometers

If in the 18th century there was a “boom” of discoveries in the field of temperature measurement systems, today work is increasingly being carried out to create methods for measuring temperature.

The scope of application of thermometers is extremely wide and is of particular importance for modern life person. A thermometer outside the window reports the temperature outside, a thermometer in the refrigerator helps control the quality of food storage, a thermometer in the oven allows you to maintain the temperature when baking, and a thermometer measures body temperature and helps assess the causes of poor health.
A thermometer is the most common type of thermometer, and it is the one that can be found in every home. However, mercury thermometers, which were once a brilliant discovery by scientists, are now gradually becoming a thing of the past as unsafe. Mercury thermometers contain 2 grams of mercury and have the highest accuracy in determining temperature, but you not only need to handle them correctly, but also know what to do if the thermometer suddenly breaks.
Mercury thermometers are being replaced by electronic or digital thermometers, which operate on the basis of a built-in metal sensor. There are also special thermal strips and infrared thermometers.

3. Find the weight of the body P = ρgV

4. Determine the pressure exerted by the body on the horizontal surface P = , where F=P

Experimental work No. 12

Topic: “Study of the dependence of thermometer readings on external conditions.”

Target: examine the dependence of the thermometer readings depending on external conditions: whether the sun’s rays fall on the thermometer or whether it is in the shade, what kind of substrate the thermometer is on, what color the screen covers the thermometer from the sun’s rays.

Tasks:

Educational: instilling accuracy, the ability to work in a team;

Equipment: table lamp, thermometer, sheets of white and black paper.

What is the air temperature in the room and outside? People are interested every day. There is a thermometer for measuring air temperature in almost every home, but not every person knows how to use it correctly. Firstly, many do not understand the very task of measuring air temperature. This misunderstanding is especially evident on hot summer days. When meteorologists report that the air temperature in the shade reached 32°C, many people “clarify” something like this: “And in the sun the thermometer went beyond 50°C!” Do such clarifications make sense? To answer this question, carry out the following experimental study and draw your own conclusions.

Progress:

Experiment 1. Measure the air temperature “in the sun” and “in the shade”. Use a table lamp as the “Sun”.

The first time, place the thermometer at a distance of 15-20 cm from the lamp on the table, the second time, without changing the location of the lamp relative to the thermometer, create a “shadow” with a sheet of paper, placing it near the lamp. Record the thermometer readings.

Experiment 2. Take temperature measurements “in the sun” using first a dark, then a light substrate under the thermometer. To do this, place the thermometer on a sheet of white paper the first time, and on a sheet of black paper the second time. Record the thermometer readings.

Experiment 3. Take measurements “in the shadow”, blocking the light from the lamp with a sheet of white paper placed directly on the thermometer. Record the thermometer readings. Repeat the experiment, replacing the white paper with black paper.

Consider the results of the experiments performed and draw conclusions: where and how should a thermometer be mounted outside the window to measure the air temperature outside?

A series of experiments, when performed correctly, gives the following results.

Experiment 1 shows that the thermometer readings “in the sun” are noticeably higher than its readings “in the shade.” This fact must be explained as follows. In the absence of sunlight, the temperatures of the air and the table are the same. As a result of heat exchange with the table and air, the thermometer comes into thermal equilibrium with them and shows the air temperature.

When the “sun” is not covered by a sheet of paper, under the influence of the absorbed radiation of the “sun” the temperature of the table rises, and the transparent air is almost not heated by this radiation. The thermometer, on the one hand, exchanges heat with the surface of the table, and on the other hand, with the air. As a result, its temperature is higher than the air temperature, but lower than the table surface temperature. What then is the meaning of the thermometer readings “in the sun”?

A persistent lover of measuring air temperature “in the sun” can object to this that he is not interested in the air temperature “in the shade” when he himself is “in the sun”. Let it not be the air temperature, just the readings of the thermometer “in the sun,” but they are precisely what interests him. In this case, the results of experiment 2 will be useful to him.

Experiment 2 shows that on white paper, which reflects light well, the thermometer readings are significantly lower than on black paper, which absorbs light well and heats up more. Consequently, there is no clear answer to the question about the thermometer readings “in the sun”. The result will greatly depend on the color of the substrate under the thermometer, the color and structure of the surface of the thermometer balloon, and the presence or absence of wind.

The outdoor air temperature, when measured far from objects heated by solar radiation and excluding the direct influence of radiation on the thermometer, is the same “in the sun” and “in the shade”; it is simply the air temperature. But it should really only be measured “in the shadows.”

But creating a “shadow” for a thermometer on a sunny day is also not simple task. This is confirmed by the results of experiment 3. They show that if the screen is located close to the thermometer, heating of the screen by solar radiation will lead to significant errors when measuring air temperature on a sunny day. The temperature increase will be especially large when the screen is dark, since such a screen absorbs almost all the energy of solar radiation incident on it, and much less when the screen is white, since such a screen reflects almost all the energy of solar radiation incident on it.

After doing this experimental research It is necessary to discuss a practically important question: how in practice should one measure the air temperature outside? The answer to this question might be something like this. If the apartment has a window facing north, then it is behind this window that you need to strengthen the outdoor thermometer. If there is no such window in the apartment, the thermometer should be placed as far as possible from the walls heated by the sun, opposite the weakly heated window panes. The thermometer bottle must be protected from heating by solar radiation. The results of experiment 3 show that when trying to protect the thermometer from solar radiation, the screen itself heats up and heats the thermometer. Since the white screen heats up less, the protective screen should be light and should be located at a sufficient distance from the thermometer.

A similar thing can be done to study the dependence of the readings of a room thermometer on its location. The result of execution homework there must be an establishment of the fact that the readings of a room thermometer depend on its location in the room. If we are interested in the air temperature in the room, then we need to exclude the influence of heated bodies and solar radiation on it. The thermometer should not be exposed to direct sunlight; the thermometer should not be placed near heating or lighting devices. You should not hang a thermometer on the outer wall of a room, which has a high temperature in summer and a low temperature in winter relative to the air temperature in the room.

Experimental work No. 13

Topic: “Determination of the percentage of snow in water.”

Target: Determine the percentage of snow in the water.

Tasks:

Educational: developing the ability to combine knowledge and practical skills;

Educational: development logical thinking, cognitive interest.

Equipment: calorimeter, thermometer, beaker, vessel with room water, mixture of snow and water, calorimetric body.

First option

Progress:

1. So much water is poured into the calorimeter with the mixture so that all the snow melts. The temperature of the resulting water was equal to t=0.

2. Let’s write down the heat balance equation for this case:

m1 =сm3(t2-t1), where с - specific heat water, is the specific heat of melting of ice, m1 is the mass of snow, m2 is the mass of water in the snow, m3 is the mass of poured water, t is the temperature of poured water.

Hence =

Required percentage =;

3. The value m1 + m2 can be determined by pouring all the water from the calorimeter into the measuring cylinder and measuring the total mass of water m. Since m= m1 + m2 + m3, then

m1 + m2 = m - m3. Hence,

=

Second option

Equipment: calorimeter, thermometer, scales and weights, a glass of warm water, a lump of wet snow, a calorimetric body.

Progress:

1. Weigh the empty calorimeter, and then the calorimeter with a lump of wet snow. From the difference we determine the mass of a lump of wet snow (m).

The lump contains *x grams of water and *(100 - x) grams of snow, where x is the percentage of water in the lump.

Wet snow temperature 0.

2.Now add so much to the calorimeter with a lump of wet snow warm water(mв) so that all the snow melts, after first measuring the temperature of warm water (to).

3. We weigh the calorimeter with water and melted snow and, based on the difference in weights, determine the mass of added warm water (mw).

4.Measure the final temperature (tocm) with a thermometer.

5. Let’s write down the heat balance equation:

cmв t = *(100 - x) + с(m+ mв) tocm.,

Where c is the specific heat capacity of water - 4200 J/kg , - specific heat of melting of snow

3.3 *105 J/kg.

6. From the resulting equation we express

X=100 -

Experimental work No. 14

Topic: “Determination of the heat of fusion of ice.”

Target: determine the heat of fusion of ice .

Tasks:

Educational: developing the ability to combine knowledge and practical skills;

Educational: instilling accuracy, the ability to work in a team;

Developmental: development of logical thinking, cognitive interest.

Equipment: thermometer, water, ice, graduated cylinder.

Progress:

1. Place a piece of ice in an empty container and pour enough water into it from the measuring cylinder until all the ice melts.

2. In this case, the heat balance equation will be written simply:

St1 (t1 - t2) = t2

where t2 is the mass of ice, tx is the mass of poured water, tx is the initial temperature of water, t2 is the final temperature of water equal to O °C, K is the specific heat of melting of ice. From the above equation we find:

3.The mass of ice can be determined by draining the resulting water into a measuring cylinder and measuring the total mass of water and ice:

M = + m2 = ρадь, Vtot.

Since m2 = M - m1, then

Experimental work No. 15

Target: using the proposed equipment and a table of the dependence of saturated vapor pressure on temperature, determine the absolute and relative humidity in the room.

Tasks:

Educational: developing the ability to combine knowledge and practical skills;

Educational: instilling accuracy, the ability to work in a team;

Developmental: development of logical thinking, cognitive interest.

Equipment: glass, thermometer, ice, water.

Progress:

1.The easiest way to determine absolute air humidity is by the dew point. To measure the dew point, you must first measure the temperature t1 of the air. Then take an ordinary glass glass, pour a little water into it at room temperature and place a thermometer in the water.

2. In another vessel you need to prepare a mixture of water and ice and from this vessel add little cold water into a glass with water and a thermometer until dew appears on the walls of the glass. You need to look at the wall of the glass opposite the water level in the glass. When the dew point is reached, the wall of the glass below the water level becomes dull due to the many small droplets of dew condensing on the glass. At this moment, you need to take the readings of the t2 thermometer.

3. Based on the value of temperature t2 - the dew point - the density ρ of saturated steam at temperature t2 can be determined from the table. It will be absolute humidity atmospheric air. Then you can find from the table the value of density r0 of saturated steam at temperature t1. Based on the found values ​​of saturated steam density r at temperature t2 and saturated steam density ρ0 at room temperature t1, the relative air humidity j is determined.

Errors of measuring instruments

	Measuring	Measurement limit	Value of division	Instrumental error
	Student ruler
	Drawing ruler
	Tool ruler
	Demonstration line
	Measuring tape
	Beaker
	Training scales
	Set of weights G-4-211.10
	Laboratory weights
	School caliper
	Micrometer
	Training dynamometer
	Electronic stopwatch KARSER			±0.01 s (0.2 s taking into account subjective error).
	Aneroid barometer	780 mm. rt. Art.	1 mm. rt. Art.	±3 mm. rt. Art.
	Laboratory thermometer
	Open demonstration pressure gauge

Density of liquids, metals and alloys, solids and materials.

ρ, kg/m3