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Thomsen–Berthelot Principle
In thermochemistry, the Thomsen–Berthelot principle is a hypothesis in the history of chemistry which argued that all chemical changes are accompanied by the production of heat and that processes which occur will be ones in which the most heat is produced. This principle was formulated in slightly different versions by the Danish chemist Julius Thomsen in 1854 and by the French chemist Marcellin Berthelot in 1864. This early postulate in classical thermochemistry became the controversial foundation of a research program that would last three decades. This principle came to be associated with what was called the ''thermal theory of affinity'', which postulated that the heat evolved in a chemical reaction was the true measure of its affinity. This hypothesis was later disproved, however, when in 1882 the German scientist Hermann von Helmholtz Hermann Ludwig Ferdinand von Helmholtz (31 August 1821 – 8 September 1894) was a German physicist and physician who made signi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermochemistry
Thermochemistry is the study of the heat energy which is associated with chemical reactions and/or phase changes such as melting and boiling. A reaction may release or absorb energy, and a phase change may do the same. Thermochemistry focuses on the energy exchange between a system and its surroundings in the form of heat. Thermochemistry is useful in predicting reactant and product quantities throughout the course of a given reaction. In combination with entropy determinations, it is also used to predict whether a reaction is spontaneous or non-spontaneous, favorable or unfavorable. Endothermic reactions absorb heat, while exothermic reactions release heat. Thermochemistry coalesces the concepts of thermodynamics with the concept of energy in the form of chemical bonds. The subject commonly includes calculations of such quantities as heat capacity, heat of combustion, heat of formation, enthalpy, entropy, and free energy. Thermochemistry is one part of the broader field o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
History Of Chemistry
The history of chemistry represents a time span from ancient history to the present. By 1000 BC, civilizations used technologies that would eventually form the basis of the various branches of chemistry. Examples include the discovery of fire, extracting metals from ores, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap, making glass, and making alloys like bronze. The protoscience of chemistry, alchemy, was unsuccessful in explaining the nature of matter and its transformations. However, by performing experiments and recording the results, alchemists set the stage for modern chemistry. While both alchemy and chemistry are concerned with matter and its transformations, chemists are seen as applying scientific method to their work. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard Gibbs. Ancient history Early humans A 100,00 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Process
In a scientific sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by an outside force, and involves a chemical reaction of some sort. In an "engineering" sense, a chemical process is a method intended to be used in manufacturing or on an industrial scale (see Industrial process) to change the composition of chemical(s) or material(s), usually using technology similar or related to that used in chemical plants or the chemical industry. Neither of these definitions are exact in the sense that one can always tell definitively what is a chemical process and what is not; they are practical definitions. There is also significant overlap in these two definition variations. Because of the inexactness of the definition, chemists and other scientists use the term "chemical process" only in a general sense or in the engineering sense. However, in the "process (engineer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is also often used to refer to the thermal energy contained in a system as a component of its internal energy and that is reflected in the temperature of the system. For both uses of the term, heat is a form of energy. An example of formal vs. informal usage may be obtained from the right-hand photo, in which the metal bar is "conducting heat" from its hot end to its cold end, but if the metal bar is considered a thermodynamic system, then the energy flowing within the metal bar is called internal energy, not heat. The hot metal bar is also transferring heat to its surroundings, a correct statement for both the strict and loose meanings of ''heat''. Another example of informal usage is the term '' heat content'', used despite the fact tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Julius Thomsen
The gens Julia (''gēns Iūlia'', ) was one of the most prominent patrician families in ancient Rome. Members of the gens attained the highest dignities of the state in the earliest times of the Republic. The first of the family to obtain the consulship was Gaius Julius Iulus in 489 BC. The gens is perhaps best known, however, for Gaius Julius Caesar, the dictator and grand uncle of the emperor Augustus, through whom the name was passed to the so-called Julio-Claudian dynasty of the first century AD. The Julius became very common in imperial times, as the descendants of persons enrolled as citizens under the early emperors began to make their mark in history.''Dictionary of Greek and Roman Biography and Mythology'', vol. II, pp. 642, 643. Origin The Julii were of Alban origin, mentioned as one of the leading Alban houses, which Tullus Hostilius removed to Rome upon the destruction of Alba Longa. The Julii also existed at an early period at Bovillae, evidenced by a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marcellin Berthelot
Pierre Eugène Marcellin Berthelot (; 25 October 1827 – 18 March 1907) was a French chemist and Republican politician noted for the ThomsenBerthelot principle of thermochemistry. He synthesized many organic compounds from inorganic substances, providing a large amount of counter-evidence to the theory of Jöns Jakob Berzelius that organic compounds required organisms in their synthesis. Berthelot was convinced that chemical synthesis would revolutionize the food industry by the year 2000, and that synthesized foods would replace farms and pastures. "Why not", he asked, "if it proved cheaper and better to make the same materials than to grow them?" He was considered "one of the most famous chemists in the world." Upon being appointed to the post of Minister of Foreign Affairs for the French government in 1895, he was considered "the most eminent living chemist" in France. In 1901, he was elected as one of the "Forty Immortals" of the Académie française. He gave all his ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Affinity
In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds. Chemical affinity can also refer to the tendency of an atom or compound to combine by chemical reaction with atoms or compounds of unlike composition. History Early theories The idea of ''affinity'' is extremely old. Many attempts have been made at identifying its origins. The majority of such attempts, however, except in a general manner, end in futility since "affinities" lie at the basis of all magic, thereby pre-dating science. Physical chemistry, however, was one of the first branches of science to study and formulate a "theory of affinity". The name ''affinitas'' was first used in the sense of chemical relation by German philosopher Albertus Magnus near the year 1250. Later, those as Robert Boyle, John Mayow, Johann Glauber, Isaac Newton, and Georg Stahl put forward ideas on elective affinity in at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermann Von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz (31 August 1821 – 8 September 1894) was a German physicist and physician who made significant contributions in several scientific fields, particularly hydrodynamic stability. The Helmholtz Association, the largest German association of research institutions, is named in his honor. In the fields of physiology and psychology, Helmholtz is known for his mathematics concerning the eye, theories of vision, ideas on the visual perception of space, color vision research, the sensation of tone, perceptions of sound, and empiricism in the physiology of perception. In physics, he is known for his theories on the conservation of energy, work in electrodynamics, chemical thermodynamics, and on a mechanical foundation of thermodynamics. As a philosopher, he is known for his philosophy of science, ideas on the relation between the laws of perception and the laws of nature, the science of aesthetics, and ideas on the civilizing p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermodynamic Free Energy
The thermodynamic free energy is a concept useful in the thermodynamics of chemical or thermal processes in engineering and science. The change in the free energy is the maximum amount of work that a thermodynamic system can perform in a process at constant temperature, and its sign indicates whether the process is thermodynamically favorable or forbidden. Since free energy usually contains potential energy, it is not absolute but depends on the choice of a zero point. Therefore, only relative free energy values, or changes in free energy, are physically meaningful. The free energy is a thermodynamic state function, like the internal energy, enthalpy, and entropy. The free energy is the portion of any first-law energy that is available to perform thermodynamic work at constant temperature, ''i.e.'', work mediated by thermal energy. Free energy is subject to irreversible loss in the course of such work. Since first-law energy is always conserved, it is evident that free energ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reversible Process (thermodynamics)
In thermodynamics, a reversible process is a process, involving a system and its surroundings, whose direction can be reversed by infinitesimal changes in some properties of the surroundings, such as pressure or temperature. Throughout an entire reversible process, the system is in thermodynamic equilibrium, both physical and chemical, and ''nearly'' in pressure and temperature equilibrium with its surroundings. This prevents unbalanced forces and acceleration of moving system boundaries, which in turn avoids friction and other dissipation. To maintain equilibrium, reversible processes are extremely slow ( ''quasistatic''). The process must occur slowly enough that after some small change in a thermodynamic parameter, the physical processes in the system have enough time for the other parameters to self-adjust to match the new, changed parameter value. For example, if a container of water has sat in a room long enough to match the steady temperature of the surrounding air ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Principle Of Maximum Work
In the history of science, the principle of maximum work was a postulate concerning the relationship between chemical reactions, heat evolution, and the potential thermodynamic work, work produced there from. The principle was developed in approximate form in 1875 by French chemist Marcellin Berthelot, in the field of thermochemistry, and then in 1876 by American mathematical physicist Willard Gibbs, in the field of thermodynamics, in a more accurate form. Berthelot's version was essentially: "every pure chemical reaction is accompanied by evolution of heat." (and that this yields the maximum amount of work). The effects of irreversibility, however, showed this version to be incorrect. This was rectified, in thermodynamics, by incorporating the concept of entropy. Overview Berthelot independently enunciated a generalization (commonly known as Berthelot's Third Principle, or Principle of Maximum Work), which may be briefly stated as: every pure chemical reaction is accompanied by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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