Regarding temperature and heat?

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This post was last edited by imummyi on 2011-5-5 11:06. I have a question that has always puzzled me! ! ! Question 1: Who first came up with the concept of temperature, and how? Or perhaps it wasn’t a particular person or organization, but rather emerged naturally during a certain period – when was that roughly? Question 2: In the 17th and 18th centuries, the units for measuring heat were primarily calories and BTU. But who was the first to propose and establish these units? Is Calorie a personal name? PS: Cold and heat are innate sensations (what is actually perceived is the temperature difference; absolute temperature cannot be sensed, meaning it cannot be measured. To say that an object is cold or hot, it must be compared to another object, or to an object that was in contact with it some time ago). There is no need for any explanation – it’s common sense. In mathematical terms, this is an axiom; in physics, it’s a law that goes without proof. Anyone can perceive cold and heat, and the definition of temperature is based on this. By definition, a hot object has a higher temperature than a cold object (why wasn’t it said originally that a cold object has a lower temperature than a hot one?) ), and then one can choose a reference (the selection of a substance for temperature measurement). Now that we have the concept of high or low temperature, how do we measure it? It is necessary to choose some property of the object that can change with changes in temperature, or in other words, that can change as heat flows. The question is: how do we know that these changes are caused by temperature? ), and the selection of scales. -2: Did humans first have the concept of temperature or the concept of heat? The idea that \"heat is a form of matter\" appears in the writings of Democritus and Epicurus in ancient Greece, as well as in Lucretius’ works from ancient Rome. This shows that humans began to understand and study heat and thermal energy very early on. It seems that there isn’t much difference between thermal energy – the amount of heat – and what heat actually is, whether heat is considered a form of matter or energy. Therefore, the theory of caloric played a significant role in the measurement of heat; it is also relatively easy to understand and aligns well with human everyday thinking and reasoning. Among heat, thermal energy, and temperature, what humans perceived first was likely temperature, which in modern terms refers to heat or the difference in temperature. Next came the concept of heat itself, with attempts to explain and model it (heat being a property of matter), and finally, research was conducted on the quantity of heat. So it can be said that the concept of heat was established quite early on; it’s just that later on a different term was used, namely \"temperature\" (which meant quantification). In my understanding, the theory of caloric was popular because, in an era without the concept of temperature or the ability to measure it quantitatively, considering heat as a form of matter was very helpful for understanding it. -1. So, which comes first: heat or temperature? The definition and measurement of heat intensity seem not to depend on heat itself, but rather on the choice of temperature-measuring substance ； The second is the determination of the scale standard. The measurement of heat, on the other hand, depends on temperature, as the definition at that time seemed to be the amount of heat absorbed or released per unit increase or decrease in temperature. But as mentioned earlier, that era was the era of the phlogiston theory; in other words, research focused on the quantity of a certain substance, so there was no need for the concept of heat. Was the calorie unit introduced during that time? But how was heat measured back then? 0. In 1593, Galileo invented the first air thermometer. By this time, humanity already had a fairly good understanding of the qualitative concept of temperature, which led them to attempt to measure it quantitatively for practical purposes (such as measuring body temperature). Santorius, a medical professor at the University of Padua, invented the first thermometer for measuring body temperature in 1600; it is now known that the variations in body temperature are quite small, which indicates that thermometers already had high precision during Galileo’s time. But where does the word “temperature” come from? When was it formed? It seems to be related to the body’s temperature, because in modern English dictionaries, one of the meanings of the word \"temperature\" is to indicate the degree of warmth or coldness in the human body. -----Temperature, the degree of cold or heat – humans are able to perceive cold and heat, and to sense that objects have varying degrees of temperature. But just how cold or hot it is, what is used to measure it? What is the method for measurement? Galileo was probably the first person to quantify temperature in a relatively precise manner. What did Galileo call the concept of \"temperature\" at that time? (It must have been some Italian word.) 1. It was not until 1709 that Fahrenheit invented the first practical alcohol thermometer. Although temperature measurement had already begun prior to that, it was not very accurate. (As for how the concept of temperature originated, before that era, humans only had a subjective understanding of whether things were cold or hot; there was no standardized value used to measure coldness and heat.) In 1714, Fahrenheit replaced water with mercury as the substance for measuring temperature, creating the first empirical temperature scale in history—the Fahrenheit scale—which established a unified standard for temperature measurement for the first time. It was not until 1742 that Celsius established the Celsius temperature scale. The thermodynamic temperature scale came even later, being established in 1848. Now, working backwards, humanity had to be able to measure temperature accurately before the concept of heat measurement could be introduced (although the concept of heat must have existed earlier, in the form of only a perceptual understanding); in other words, the unit for heat must have been proposed or established after 1709. --------------Also, in that era, the understanding of heat was still dominated by the phlogiston theory. Caloric theory: Is the calorie a unit derived from the caloric theory? 2. The concept of specific heat was introduced by Black in the 1770s; it helped to distinguish between temperature and heat. Before this, people did not fully understand the relationship between these two concepts. With the introduction of the concept of specific heat, it became possible to have a fairly thorough understanding of heat and temperature. Therefore, it can be inferred that by around 1770, the concept of heat had already been recognized and measured, in other words, units for measuring heat already existed at that time. 3. Under the theory of caloric theory, can work and heat be converted into each other? A temperature difference can lead to the transfer of thermal mass, and thermal mass is conserved – it cannot be created nor destroyed. The idea that friction generates heat is simply the release of \"latent heat\" (different from the modern concept). So what exactly did Rutherford and Davy’s experiments prove? And what about Joule’s experiments? It seems that no issues were clarified in any of these experiments! ! The phlogiston theory holds that phlogiston is conserved; heat and work are two distinct concepts that cannot be converted into one another (or the connection between them was not even recognized). Heat is a massless substance that is attached to matter, while work can only result from the release of phlogiston already present within an object, rather than from its transformation into phlogiston. Looking at Joule’s experiment, the concept of energy conservation already existed in that era, but it applied only to kinetic energy and potential energy; heat was not taken into account. In Joule’s experiment, as the weight fell, its potential energy decreased, yet neither the temperature of the weight nor that of the surrounding air changed. The temperature of the water in the container increased. Even so, this could only prove that work was converted into heat. However, humans had already been using work for a long time; they knew that \"work could generate heat,\" but they did not connect this with heat. For example, when an object in motion eventually stops, where does its kinetic energy go? How was that explained back then? ? 4. To put an end to the confusion in temperature scales, Kelvin (i.e., W. Thomson) – the founder of the second law of thermodynamics and one of the most respected physicists – created an absolutely accurate absolute temperature scale that does not depend on any temperature medium (and thus on no physical properties of such a medium). This scale is also known as the Kelvin scale or the thermodynamic scale. The Kelvin scale is established based on the Carnot cycle, using the heat involved in this cycle as a means to measure temperature; in other words, heat serves as the substance used for temperature measurement. For this very reason, we also call the Kelvin scale the thermodynamic scale. The Carnot cycle depicts the basic pattern of an ideal heat engine and holds great theoretical significance. The Carnot cycle acts like a lighthouse in the fog, indicating the upper limit for the efficiency of heat engines. How to understand it without relying on any temperature-sensitive substance? How is it possible to have a temperature without relying on any temperature-measuring substance? Temperature is an attribute of matter; without matter, talking about temperature makes no sense. It’s impossible to have an absolute temperature independent of matter, and this notion seems to be misleading. The absolute temperature scale still relies on reference points; it requires the assumption of at least two such points, as well as a curve showing the difference between these two points, in order to define temperature. If the selected reference points are the same but different temperature-measuring substances are used, then the established temperature scales will not be exactly identical, as their physical properties may not remain constant within the same range as temperature changes. The table below lists five types of thermometers; their measuring media are hydrogen, air, platinum wire, thermocouples, and mercury respectively, while the physical properties used for temperature measurement are the pressure of gases, resistance, electromotive force, and the length of mercury. Their reference points are set at 0 degrees and 100 degrees, corresponding to the melting point of ice and the boiling point of water. It can be seen that, for the same absolute temperature (assuming the reading of a constant-volume hydrogen thermometer as the standard), the readings of various thermometers differ. 　　The above clearly illustrates our argument: no matter what type of thermometer is used to measure temperature, it merely reflects the properties of the substance being measured, along with the influence of the thermometer’s structure. For example, the bulb and capillary tube of a mercury thermometer will have their zero point altered depending on whether they contain sodium, potassium, or both. Therefore, no thermometer can measure the true temperature of an object. Due to the different choices of temperature-measuring substances and properties, as well as different approaches to selecting reference points and scales, there can be a variety of temperature scales. It was published in 1824 in a work titled Réflexions sur la Puissance Motrice du Feu, by M. S. Carnot. Having never come across the original work, the Author only became aware of Carnot’s theory through a paper by M. Clapeyron on the same subject, published in the Journal de l’École Polytechnique, Volume V, 1834, and translated in the first volume of Taylor’s Scientific Memoirs.—W.T. In summary, the unit of heat must have been proposed during the period from 1709 to 1770, defined, and fully understood and compared at that time! I would like to ask the experts in chemical thermodynamics: questions 1 and 2?