1. Physical chemistry: purpose, objectives, research methods. Basic concepts of physical chemistry.
Phys. chemistry - the science of the laws of chemical processes and chemistry. phenomena.
Subject of physical chemistry explanation of chemistry. phenomena based on more general laws of physics. Physical chemistry considers two main groups of questions:
1. Study of the structure and properties of matter and its constituent particles;
2. Study of the processes of interaction of substances.
Physical chemistry aims to study the connections between chemical and physical phenomena. Knowledge of such connections is necessary in order to deeply study the chemical reactions that occur in nature and are used in technology. processes, control the depth and direction of the reaction. The main goal of the discipline Physical Chemistry is the study of general connections and laws of chemistry. processes based on fundamental principles of physics. Physical chemistry uses physical. theories and methods for chemical phenomena.
It explains WHY and HOW transformations of substances occur: chemistry. reactions and phase transitions. WHY – chemical thermodynamics. HOW - chemical kinetics.
Basic concepts of physical chemistry
The main object of chemistry. thermodynamics is a thermodynamic system. Thermodynamic system – any body or set of bodies capable of exchanging energy and matter with themselves and with other bodies. Systems are divided into open, closed and isolated. Open and I - The thermodynamic system exchanges both substances and energy with the external environment. Closed and I - a system in which there is no exchange of matter with the environment, but it can exchange energy with it. Isolated and I -system volume remains constant and is deprived of the opportunity to exchange energy and matter with the environment.
The system may be homogeneous (homogeneous) or heterogeneous (heterogeneous) ). Phase - this is part of a system that, in the absence of an external force field, has the same composition at all its points and the same thermodynamics. St. you and is separated from other parts of the system by an interface. The phase is always uniform, i.e. homogeneous, therefore a single-phase system is called homogeneous. A system consisting of several phases is called heterogeneous.
The properties of the system are divided into two groups: extensive and intensive.
Thermodynamics uses the concepts of equilibrium and reversible processes. Equilibrium is a process passing through a continuous series of equilibrium states. Reversible thermodynamic process is a process that can be carried out in reverse without leaving any changes in the system or environment.
2. First law of thermodynamics. Internal energy, heat, work.
First law of thermodynamics directly related to the law of conservation of energy. Based on this law, it follows that in any isolated system the energy supply remains constant. From the law of conservation of energy follows another formulation of the first law of thermodynamics - the impossibility of creating a perpetual motion machine (perpetuum mobile) of the first kind, which would produce work without expending energy on it. A particularly important formulation for chemical thermodynamics
The first principle is to express it through the concept of internal energy: internal energy is a function of state, i.e. its change does not depend on the path of the process, but depends only on the initial and final state of the system. Change in internal energy of the system U can occur due to heat exchange Q and work W with the environment. Then from the law of conservation of energy it follows that the heat Q received by the system from the outside is spent on the increase in internal energy ΔU and the work W performed by the system, i.e. Q =Δ U+W. Given at alignment is
mathematical expression of the first law of thermodynamics.
Ibeginning of thermodynamics its wording:
in any isolated system the energy supply remains constant;
different forms of energy transform into each other in strictly equivalent quantities;
perpetual motion machine (perpetuum mobile) of the first kind is impossible;
internal energy is a function of state, i.e. its change does not depend on the path of the process, but depends only on the initial and final state of the system.
analytical expression: Q = D U + W ; for an infinitesimal change in quantities d Q = dU + d W .
The first law of thermodynamics establishes the relation. m / y heat Q, work A and change in internal. energy of the system ΔU. Change internal the energy of the system is equal to the amount of heat imparted to the system minus the amount of work done by the system against external forces.
Equation (I.1) is a mathematical representation of the 1st law of thermodynamics, equation (I.2) is for an infinitesimal change in state. systems.
Int. energy is a function of state; this means that the change is internal. energy ΔU does not depend on the path of transition of the system from state 1 to state 2 and is equal to the difference in the internal values. energies U2 and U1 in these states: (I.3)
Int. The energy of the system is the sum of the potential energy of the interaction. all particles of the body in relation to each other and the kinetic energy of their movement (without taking into account the kinetic and potential energies of the system as a whole). Int. the energy of the system depends on the nature of the substance, its mass and the parameters of the state of the system. She's age. with an increase in the mass of the system, since it is an extensive property of the system. Int. energy is denoted by the letter U and expressed in joules (J). In general, for a system with a quantity of 1 mole. Int. energy, like any thermodynamic. The sacredness of the system is a function of the state. Only internal changes appear directly in the experiment. energy. That is why in calculations they always operate with its change U2 –U1 = U.
All internal changes energies are divided into two groups. The 1st group includes only the 1st form of transition of motion through chaotic collisions of molecules of two contacting bodies, i.e. by thermal conduction (and at the same time by radiation). The measure of the movement transmitted in this way is heat. Concept warmth is associated with the behavior of a huge number of particles - atoms, molecules, ions. They are in constant chaotic (thermal) motion. Heat is a form of energy transfer. The second way to exchange energy is Job. This exchange of energy is caused by an action performed by the system or an action performed on it. Usually the work is indicated by the symbol W. Work, like heat, is not a function of the state of the system, therefore the quantity corresponding to infinitesimal work is denoted by the partial derivative symbol - W.
PHYSICAL CHEMISTRY - a branch of chemistry devoted to the study of the relationship between chemical and physical phenomena in nature. Provisions and methods of F. x. are important for medicine and biomedical sciences, methods of Physics. are used to study life processes both normally and in pathology.
The main subjects of study of Ph. x. are the structure of atoms (see Volume A) and molecules (see Molecule), the nature of chemicals. connections, chemistry equilibrium (see Chemical equilibrium) and kinetics (see Chemical kinetics, Kinetics of biological processes), catalysis (see), theory of gases (see), liquids and solutions (see), structure and chemistry. properties of crystals (see) and polymers (see High-molecular compounds), thermodynamics (see) and thermal effects of chemistry. reactions (see Thermochemistry), surface phenomena (see Detergents, Surface tension, Wetting), properties of electrolyte solutions (see), electrode processes (see Electrodes) and electromotive forces, corrosion of metals, photochemical. and radiation processes (see Photochemical reactions, Electromagnetic radiation). Most theories of F. x. is based on the laws of statics, quantum (wave) mechanics and thermodynamics. When studying the problems posed in F. x. Various combinations of experimental methods of physics and chemistry, so-called, are widely used. Phys.-Chem. methods of analysis, the basics of which were developed in 1900-1915.
To the most common physical and chemical methods of the second half of the 20th century. include electron paramagnetic resonance (see), nuclear magnetic resonance (see), mass spectrometry (see), the use of the Mössbauer effect (nuclear gamma resonance), radio spectroscopy (see Spectroscopy), spectrophotometry (see) and fluorimetry (see), X-ray diffraction analysis (see), electron microscopy (see), centrifugation (see), gas and liquid chromatography (see), electrophoresis (see), isoelectric focusing (see), polarography (see), potentiometry (see Potentiometric titration), conductometry (see), osmometry (see Osmotic pressure), ebulliometry (see), etc.
The term “physical chemistry” first appeared in the works of German. alchemist Kuhnrath (H. Kuhnrath, 1599), but for a long time the meaning put into this term did not correspond to its true meaning. The problems of physical chemistry, close to their modern understanding, were first formulated by M. V. Lomonosov in the course “Introduction to True Physical Chemistry,” which he read in 1752 to students of the St. Petersburg Academy of Sciences: physical chemistry, according to M. V. Lomonosov, there is a science that explains, on the basis of the principles and experiments of physics, what happens in mixed bodies during chemical reactions. reactions. Systematic teaching of Physics. was started in 1860 at Kharkov University by N. N. Beketov, who was the first to organize a physicochemical department at the natural sciences department of this university. Following the Kharkov University, the teaching of Physics. was introduced in the Kazan (1874), Yuryevsky (1880) and Moscow (1886) high fur boots. Since 1869, the journal of the Russian Physico-Chemical Society began to be published. Abroad, the Department of Physical Chemistry was first established in Leipzig in 1887.
Formation of F. x. as an independent scientific discipline is associated with atomic-molecular science, i.e., primarily with the discovery in 1748-1756. M.V. Lomonosov and in 1770-1774. A. Lavoisier's law of conservation of mass of substances in chemistry. reactions. The works of Richter (J. B. Richter, 1791 - 1802), who discovered the law of shares (equivalents), Proust (J. L. Proust, 1808), who discovered the law of constancy of composition, and others contributed to the creation in 1802-1810. J. Dalton's atomic theory and the discovery of the law of multiple ratios, which establishes the laws of chemical formation. connections. In 1811, A. Avogadro introduced the concept of “molecule,” connecting the atomic theory of the structure of matter with the laws of ideal gases. The logical conclusion of the formation of atomistic views on the nature of matter was the discovery by D. I. Mendeleev in 1869 of the periodic law of chemistry. elements (see Periodic table of chemical elements).
The modern understanding of the structure of the atom developed at the beginning
20th century The most important milestones on this path are the experimental discovery of the electron and the establishment of its charge, the creation of quantum theory (see) by Planck (M. Plank) in 1900, the work of Bohr (N. Bohr, 1913), who assumed the existence of an electron shell in the atom and who created his planetary model, and other studies that served as confirmation of the quantum theory of atomic structure. The final stage in the formation of modern ideas about the structure of the atom was the development of quantum (wave) mechanics, with the help of cutting methods it was subsequently possible to explain the nature and direction of chemistry. connections, theoretically calculate physical-chemical. constants of the simplest molecules, develop the theory of intermolecular forces, etc.
The initial development of chem. thermodynamics, which studies the laws of mutual transformations of various forms of energy in equilibrium systems, is associated with the research of S. Carnot in 1824. Further work by R. Mayer, J. Joule and G. Helmholtz led to the discovery of the conservation law energy - so-called. the first law, or the first law of thermodynamics. The introduction by R. Clausius in 1865 of the concept of “entropy” as a measure of free energy led to the development of the second law of thermodynamics. The third fundamental law of thermodynamics was derived from Nernst’s thermal theorem on the asymptotic convergence of the free energy and heat content of a system; in 1907, A. Einstein compiled the equation for the heat capacity of simple harmonic oscillators, and in
1911 Planck concluded: the entropy of pure substances at absolute zero is zero.
The beginning of the independent existence of thermochemistry - the science of thermal effects of chemistry. reactions, was founded by the works of G.I. Hess, who established in 1840 the law of constancy of heat amounts. The works of R. E. M. Berthelot were of great importance for the development of thermochemistry, who developed calorimetric methods of analysis (see Calorimetry) and discovered the principle of maximum work. In 1859, H. Kirchhoff formulated a law connecting the thermal effect of a reaction with the heat capacities of the reacting substances and reaction products. In 1909-
1912 Nernst (W. H. Nernst), Einstein and Debye (P. Debye) developed the theory of quantum heat capacity.
The development of electrochemistry, which deals with the study of the connection between chemical and electrical phenomena and the study of the effect of electric current on various substances in solutions, is associated with the creation of Volta (A. Volta) in 1792-1794. galvanic cell. In 1800, the first works on the decomposition of water by V. Nicolson and Carlyle appeared, and in 1803-1807. works of I. Berzelius and W. Hisinger on the electrolysis (see) solutions of salts. In 1833-1834. Faraday (M. Faraday) formulated the basic laws of electrolysis that relate the yield of electrochemicals. reactions with the amount of electricity and chemical. substance equivalents. In 1853-1859. Hittorf (J. W. Hittorf) established the relationship between electrochemical. action and mobility of ions, and in 1879 F. W. Kohlrausch discovered the law of independent movement of ions (see) and established a connection between equivalent electrical conductivity and the mobility of cations and anions. In 1875 - 1878 Gibbs (J. VV. Gibbs) and in 1882 G. Helmholtz developed a mathematical model connecting the electromotive force of a galvanic cell with the internal energy of a chemical. reactions. In 1879, G. Helmholtz created the doctrine of the electric double layer. In 1930-1932 Volmer (M. Vol-mer) and A. N. Frumkin proposed a quantitative theory of electrode processes.
The study of solutions began with the work of J. H. Hassenfratz (1798) and J. Gay-Lussac (1819) on the solubility of salts. In 1881 -1884. D. P. Konovalov laid the scientific foundations for the theory and practice of distillation of solutions, and in 1882, F. M. Raoult discovered the law of lowering the freezing point of solutions (see Cryometry). The first quantitative measurements of osmotic pressure (see) were made in 1877 by W. F. Ph. Pfeffer, and in 1887 J. Van't Hoff created the thermodynamic theory of dilute solutions and derived an equation relating osmotic pressure to concentration p -ra, its volume and absolute temperature. S. Arrhenius in 1887 formulated the theory of electrolytic dissociation and ionization of salts in solutions (see Electrolytes), and Nernst in 1888 - the osmotic theory. Ostwald (W. Ostwald) discovered patterns connecting the degree of dissociation of the electrolyte with its concentration. In 1911, Donnan (F. G. Don-pap) created the theory of the distribution of electrolytes on both sides of a semi-permeable membrane (see Membrane equilibrium), which found wide application in biophysical chemistry (see) and colloid chemistry (see). In 1923, Debye and E. Huckel developed a statistical theory of strong electrolytes.
Development of the doctrine of chemical kinetics. reactions, equilibrium and catalysis began with the work of L. Wilhelmy, who created the first quantitative theory of chemistry in 1850. reactions, and Williamson (A. W. Williamson), who presented equilibrium as a state of equality of the rates of forward and reverse reactions. The concept of “catalysis” was introduced into physical chemistry by I. Berzelius in
1835 Basic principles of doctrine
about chem. equilibrium were formulated in the works of Berthollet (C. L. Beg-thollet). The beginning of the dynamic theory of equilibria was laid by the works of Williamson and Clausius, the principle of moving equilibrium was developed by J. Ant-Goff, Gibbs and H. Le Chatelier. Berthelot and L. Pean-saint-Gilles established a connection between the rate of reaction and the state of equilibrium. Basic law of chemistry. kinetics about the proportionality of the reaction rate to the product of the active masses (i.e., concentrations) of the reacting substances - the law of mass action - was formulated in 1864-1867. Guldberg (S. M. Guldberg) and Waa-ge (P. Waage). In 1893-1897 A. N. Bach and K. Engler created the peroxide theory of slow oxidation (see Peroxides), in 1899-1904. Abegg and H. Bodlander developed the idea of valence as the ability of an atom to accept or give up electrons in 1913-1914. L.V. Pisarzhevsky and S.V. Dain developed the electronic theory of redox reactions (see). In 1903-1905 N. A. Shilov proposed the theory of conjugate reactions, and in 1913 Bodenstein (M. Bodenstein) discovered chain reactions (see), the theoretical foundations of which were developed in 1926 -1932. N. N. Semenov and S. N. Hinsheiwood.
The phenomenon of radioactive decay of atoms (radioactivity) was discovered in 1896 by A. Becquerel. Since then, much attention has been paid to the study of radioactivity (see), and significant progress has been achieved in this area, starting with the artificial splitting of atoms and ending with developments in controlled thermonuclear fusion. Among the problems of F. x. it is necessary to highlight the study of the influence on molecules of gamma radiation (see), the flow of high-energy particles (see Alpha radiation, Yassic radiation, Neutron radiation, Roton radiation), laser radiation (see Laser), as well as the study of reactions in electrical discharges and low-temperature plasma (plasma chemistry). Phys.-Chem. is developing successfully. mechanics, which studies the influence of surface phenomena on the properties of solids.
One of the sections of photochemistry is photochemistry (see), which studies the reactions that occur when a substance absorbs light energy from an external source of radiation.
In F. x. There is no such section that would not be important for medico-biol. disciplines and ultimately for practical medicine (see Biophysical chemistry). Phys.-Chem. methods make it possible to study living cells and tissues in vivo without subjecting them to destruction. Physics and chemistry are no less important for medicine. theories and ideas. Thus, the doctrine of the osmotic properties of solutions turned out to be extremely important for understanding water metabolism (see Water-salt metabolism) in humans under normal conditions and in pathology. The creation of the theory of electrolytic dissociation significantly influenced the idea of bioelectric phenomena (see) and laid the foundation for the ionic theory of excitation (see) and inhibition (see). The theory of acids and bases (q.v.) made it possible to explain the constancy of the internal environment of the body and served as the basis for the study of acid-base balance (q.v.). To understand the energy of life processes (for example, the functioning of ATP), studies carried out using chemical methods are widely used. thermodynamics. Development of physical-chemical ideas about surface processes (surface tension, wetting, etc.) are essential for understanding the reactions of cellular immunity (see), spreading of cells on non-cellular surfaces, adhesion, etc. Theory and methods of chemistry. kinetics are the basis for studying the kinetics of biological, primarily enzymatic, processes. A major role in understanding the essence of biol. processes are played by the study of bioluminescence, chemiluminescence (see Biochemiluminescence), the use of luminescent antibodies (see Immunofluorescence), fluoro-chroms (see), etc. to study the properties of tissue and subcellular localization of proteins, nucleic acids, etc. Phys. .-chem. methods for determining the intensity of basal metabolism (see) are extremely important in diagnosing many diseases, including endocrine ones.
It should be noted that the study of physical and chemical. properties of biol. systems and processes occurring in a living organism, makes it possible to look deeper into the essence and identify the specifics of living matter and these phenomena.
The main research centers in the field of physical chemistry in the USSR are the research institutes of the USSR Academy of Sciences, its branches and departments, the Academy of Sciences of the Union Republics: Physico-Chemical Institute named after. L. Ya. Karpova, Institute of Physical Chemistry, Institute of Chemical Physics, Institute of New Chemical Problems, Institute of Organic and Physical Chemistry named after. A. E. Arbuzova, Institute of Catalysis, Institute of Chemical Kinetics and Combustion, Institute of Physical Chemistry of the Academy of Sciences of the Ukrainian SSR, etc., as well as the corresponding departments in high fur boots.
The main publications that systematically publish articles on physical chemistry are: Journal of Physical Chemistry, Kinetics and Catalysis, Journal of Structural Chemistry, Radiochemistry, and Electrochemistry. Abroad, articles on Ph. x. published in “Zeitschrift fiir physi-kalische Chemie”, “Journal of Physical Chemistry”, “Journal de chimie physique et de physico-chimie bio-logique”.
Bibliography: Babko A.K. et al.
Physico-chemical methods of analysis, M., 1968; Kireev V. A. Course of physical chemistry, M., 1975; Melvin-Hughes
E. A. Physical chemistry, trans. from English, vol. 1 - 2, M., 1962; Nikolaev L. A. Physical chemistry, M., 1972; Development
physical chemistry in the USSR, ed. Ya. I. Gerasimova, M., 1967; Solo
Viev Yu. I. Essays on the history of physical chemistry, M., 1964; Physical
chemistry, Modern problems, ed. Ya. M. Kolotyrkina, M., 1980.
Periodicals - Journal of Structural Chemistry, M., since 1960; Journal of Physical Chemistry, M., since 1930; Kinetics and catalysis, M., since 1960; Radiochemistry, M.-L., since 1959; Electrochemistry, M., since 1965; Journal de chimie physique et de physico-chimie biologique, P., since 1903; Journal of Physical Chemistry, Baltimore, since 1896; Zeitschrift fiir physikalische Chemie, Lpz., since 1887.
Physical chemistry began in the middle of the 18th century. The term “Physical Chemistry”, in the modern understanding of the methodology of science and issues of the theory of knowledge, belongs to M. V. Lomonosov, who for the first time read the “Course of True Physical Chemistry” to students of St. Petersburg University. In the preamble to these lectures, he gives the following definition: “Physical chemistry is a science that, on the basis of physical principles and experiments, must explain the reason for what happens through chemical operations in complex bodies.” The scientist, in the works of his corpuscular-kinetic theory of heat, deals with issues that fully correspond to the above tasks and methods. This is precisely the nature of experimental actions that serve to confirm individual hypotheses and provisions of this concept. M.V. Lomonosov followed such principles in many areas of his research: in the development and practical implementation of the “science of glass”, which he founded, in various experiments devoted to confirming the law of conservation of matter and force (motion); - in works and experiments related to the study of solutions - he developed an extensive program of research into this physical and chemical phenomenon, which is in the process of development to the present day.
This was followed by a break of more than a century, and D.I. Mendeleev was one of the first in Russia to begin physical and chemical research in the late 1850s.
The next course in physical chemistry was taught by N. N. Beketov at Kharkov University in 1865.
The first department of physical chemistry in Russia was opened in 1914 at the Faculty of Physics and Mathematics of St. Petersburg University; in the fall, D. P. Konovalov’s student M. S. Vrevsky began teaching a mandatory course and practical classes in physical chemistry.
The first scientific journal intended to publish articles on physical chemistry was founded in 1887 by W. Ostwald and J. van't Hoff.
Subject of study of physical chemistry
Physical chemistry is the main theoretical foundation of modern chemistry, using theoretical methods of such important branches of physics as quantum mechanics, statistical physics and thermodynamics, nonlinear dynamics, field theory, etc. It includes the doctrine of the structure of matter, including: the structure of molecules, chemical thermodynamics, chemical kinetics and catalysis. As separate sections in physical chemistry, electrochemistry, photochemistry, physical chemistry of surface phenomena (including adsorption), radiation chemistry, the study of metal corrosion, physical chemistry of high-molecular compounds (see polymer physics), etc. are also distinguished. They are very closely related to physical chemistry and are sometimes considered as its independent sections colloid chemistry, physical-chemical analysis and quantum chemistry. Most branches of physical chemistry have fairly clear boundaries in terms of objects and methods of research, methodological features and apparatus used.
Difference between physical chemistry and chemical physics
The molecularity of an elementary reaction is the number of particles that, according to the experimentally established reaction mechanism, participate in the elementary act of chemical interaction. Monomolecular reactions- reactions in which a chemical transformation of one molecule occurs (isomerization, dissociation, etc.): H 2 S → H 2 + S Bimolecular reactions- reactions, the elementary act of which occurs when two particles (identical or different) collide: CH 3 Br + KOH → CH 3 OH + KBr Trimolecular reactions- reactions, the elementary act of which occurs when three particles collide: О 2 + NO + NO → 2NO 2 Reactions with molecularities greater than three are unknown. For elementary reactions carried out at similar concentrations of starting substances, the values of molecularity and reaction order are the same. There is no clearly defined relationship between the concepts of molecularity and reaction order, since the reaction order characterizes the kinetic equation of the reaction, and molecularity characterizes the reaction mechanism. The main directions of chemical thermodynamics are:
Chemical thermodynamics is closely related to such branches of chemistry as
Physico-chemical analysisThe theory of physical and chemical analysis is based on the principles of correspondence and continuity formulated by N. S. Kurnakov. The principle of continuity states that if new phases do not form in the system or existing ones do not disappear, then with a continuous change in the parameters of the system, the properties of individual phases and the properties of the system as a whole change continuously. The correspondence principle states that each complex of phases corresponds to a certain geometric image on the composition-property diagram. Theory of reactivity of chemical compoundsHigh energy chemistry (HEC) studies chemical reactions and transformations that occur in matter under the influence of non-thermal energy. The mechanisms and kinetics of such reactions and transformations are characterized by significantly nonequilibrium concentrations of fast, excited or ionized particles with an energy greater than the energy of their thermal motion and, in some cases, chemical bonding. Carriers of non-thermal energy acting on matter: accelerated electrons and ions, fast and slow neutrons, alpha and beta particles, positrons, muons, pions, atoms and molecules at supersonic speeds, quanta of electromagnetic radiation, as well as pulsed electric, magnetic and acoustic fields. High-energy chemistry processes are distinguished by time stages into physical, occurring in femtoseconds or less, during which non-thermal energy is distributed unevenly in the medium and a “hot spot” is formed, physical-chemical, during which nonequilibrium and inhomogeneity in the “hot spot” are manifested. and, finally, chemical, in which the transformations of matter obey the laws of general chemistry. As a result, ions and excited states of atoms and molecules are formed at room temperatures that cannot arise due to equilibrium processes. The external manifestation of CHE is the formation of ions and excited states of atoms and molecules at room temperatures, at which these particles cannot arise due to equilibrium processes. N. E. Ablesimov formulated the relaxation principle of controlling the properties of nonequilibrium physicochemical systems. In the case when the relaxation times are much longer than the duration of the physical impact, it is possible to control the release of chemical forms, phases and, as a consequence, the properties of substances (materials), using information about relaxation mechanisms in nonequilibrium condensed systems at the physicochemical stage of relaxation processes (including number and during operation). Main sections of HVE
and others. Laser chemistryElectromagnetic radiation (X-rays, γ-radiation, synchrotron radiation) and fluxes of accelerated particles (electrons, protons, neutrons, helions, heavy ions; fission fragments of heavy nuclei, etc.), the energy of which exceeds the ionization potential of atoms or molecules ( in most cases, lying in the range of 10-15 eV). Radiation chemistry examines certain chemical processes that are not possible using traditional chemical approaches. Ionizing radiation can greatly reduce the temperature of chemical reactions without the use of catalysts and initiators. History of radiation chemistry Radiation chemistry arose after the discovery of x-rays by W. Roentgen in 1895 and radioactivity by A. Becquerel in 1896, who were the first to observe radiation effects in photographic plates. The first work on radiation chemistry was carried out in 1899-1903 by the spouses M. Curie and P. Curie. In subsequent years, the largest number of studies was devoted to the radiolysis of water and aqueous solutions. Nuclear chemistryMain directions of nuclear chemistry:
ElectrochemistryElectrochemistry is a branch of chemical science that examines systems and interphase boundaries when electric current flows through them, studies processes in conductors, on electrodes (made of metals or semiconductors, including graphite) and in ionic conductors (electrolytes). Electrochemistry studies processes |
A science that explains chemical phenomena and establishes their patterns based on the general principles of physics. The name of the science Physical chemistry was introduced by M. V. Lomonosov, who for the first time (1752 1753) formulated its subject and tasks and established one... ... Big Encyclopedic Dictionary
PHYSICAL CHEMISTRY- PHYSICAL CHEMISTRY, “a science that explains, on the basis of provisions and experiments, the physical cause of what happens through chemistry. operations in complex bodies." This definition was given to it by the first physical chemist M.V. Lomonosov in a course read ... Great Medical Encyclopedia
PHYSICAL CHEMISTRY, the science that studies the physical changes associated with CHEMICAL REACTIONS, as well as the relationship between physical properties and chemical composition. The main branches of physical chemistry THERMODYNAMICS, which deals with changes in energy in ... ... Scientific and technical encyclopedic dictionary
Physical chemistry- - a branch of chemistry in which the chemical properties of substances are studied based on the physical properties of their constituent atoms and molecules. Modern physical chemistry is a broad interdisciplinary field bordering on various branches of physics... Encyclopedia of terms, definitions and explanations of building materials
PHYSICAL CHEMISTRY, explains chemical phenomena and establishes their patterns based on the general principles of physics. Includes chemical thermodynamics, chemical kinetics, the study of catalysis, etc. The term physical chemistry was introduced by M.V. Lomonosov in 1753... Modern encyclopedia
Physical chemistry- PHYSICAL CHEMISTRY, explains chemical phenomena and establishes their patterns based on the general principles of physics. Includes chemical thermodynamics, chemical kinetics, the study of catalysis, etc. The term “physical chemistry” was introduced by M.V. Lomonosov in... ... Illustrated Encyclopedic Dictionary
PHYSICAL CHEMISTRY- section of chem. science, studying chemistry. phenomena based on the principles of physics (see (1)) and physical. experimental methods. F. x. (like chemistry) includes the study of the structure of matter, chemistry. thermodynamics and chemistry kinetics, electrochemistry and colloid chemistry, teaching... ... Big Polytechnic Encyclopedia
Noun, number of synonyms: 1 physical chemistry (1) Dictionary of synonyms ASIS. V.N. Trishin. 2013… Synonym dictionary
physical chemistry- — EN physical chemistry A science dealing with the effects of physical phenomena on chemical properties. (Source: LEE) … … Technical Translator's Guide
physical chemistry- is a science that explains chemical phenomena and establishes their patterns on the basis of physical principles. Dictionary of Analytical Chemistry... Chemical terms
Books
- Physical chemistry, A. V. Artemov. The textbook was created in accordance with the Federal State Educational Standard in areas of bachelor’s training that include studying the discipline “Physical Chemistry”.…
- Physical chemistry, Yu. Ya. Kharitonov. The textbook outlines the basics of physical chemistry in accordance with the approximate program for the discipline "Physical and colloidal chemistry" for specialty 060301 "Pharmacy". The publication is intended...
There is a science that explains, on the basis of the principles and experiments of physics, what happens in mixed bodies during chemical operations." The first scientific journal intended for the publication of articles on physical chemistry was founded in 1887 by W. Ostwald and J. Van't Hoff.
F Physical chemistry is the main theoretical one. the foundation of modern chemistry, based on such important branches of physics as quantum mechanics, statistical. physics and thermodynamics, nonlinear dynamics, field theory, etc. It includes the doctrine of the structure of matter, incl. about the structure of molecules, chemical thermodynamics, chemical kinetics and catalysis. Electrochemistry, photochemistry, physical chemistry of surface phenomena (including adsorption), radiation chemistry, the study of corrosion of metals, physical chemistry of high molecular weight are also often distinguished as separate sections in physical chemistry. conn. etc. They are very closely related to physical chemistry and are sometimes considered as independent of it. sections colloidal chemistry, physical-chemical analysis and quantum chemistry. Most branches of physical chemistry have fairly clear boundaries in terms of objects and methods of research, methodologically. features and the device used.
Modern The stage of development of physical chemistry is characterized by an in-depth analysis of the general laws of chemistry. transformations on the pier level, widespread use of mat. modeling, expanding the range of external influences on chemical system (high and cryogenic temperatures, high pressures, strong radiation and magnetic influences), the study of ultra-fast processes, methods of energy accumulation in chemicals. in-wah, etc.
The application of quantum theory, primarily quantum mechanics, in explaining chemistry. phenomena entailed means. increased attention to the level of interpretation led to the identification of two directions in chemistry. A direction based on quantum mech. theory and operating on microscopic. level of explanation of phenomena, often called chemical. physics, but a direction that operates with ensembles of a large number of particles, where statistical principles come into force. laws - physical chemistry. With this division, the boundary between physical chemistry and chemistry. physics not m.b. carried out sharply, which is especially evident in the theory of chemical rates. districts.
The doctrine of the structure of matter and the structure of molecules summarizes an extensive experiment. material obtained using such physical methods such as molecular spectroscopy, which studies interactions. electromagnetic radiation with substances in different wavelength ranges, photo- and x-ray electron spectroscopy, electron diffraction, neutron diffraction and x-ray diffraction methods, methods based on magneto-optical. effects, etc. These methods make it possible to obtain structural data on the electronic configuration of molecules, on the equilibrium positions and amplitudes of vibrations of nuclei in molecules and condensers. in-ve, about the energy system. levels of molecules and transitions between them, changes in geom. configurations when the environment of the molecule or its individual fragments changes, etc.
Along with the task of correlating the properties of substances with their modern structure. Physical chemistry is also actively engaged in the inverse problem of predicting the structure of compounds with given properties.
A very important source of information about the structure of molecules, their characteristics in various parts. states and characteristics of chemistry. transformations are the results of quantum chemistry. calculations. Quantum chemistry provides a system of concepts and ideas that are used in physical chemistry when considering the behavior of chemicals. connections per mol. level and when establishing correlations between the characteristics of the molecules that form a substance and the properties of this substance. Thanks to the results of quantum chemistry. calculations of chemical potential energy surfaces. systems in various quantum states and experiments. With the opportunities of recent years, primarily the development of laser chemistry, physical chemistry has come close to a comprehensive study of St. in excited and highly excited states, to the analysis of the structural features of the connection. in such states and the specifics of the manifestation of these features in the dynamics of chemicals. transformations.
A limitation of conventional thermodynamics is that it can only describe equilibrium states and reversible processes. Real irreversible processes are the subject of the theory that arose in the 30s. 20th century thermodynamics of irreversible processes. This area of physical chemistry studies nonequilibrium macroscopic phenomena. systems in which the rate of entropy generation locally remains constant (such systems are locally close to equilibrium). It allows you to consider systems with chemical r-tions and mass transfer (diffusion), heat, electricity. charges, etc.
Chemical kinetics studies chemical transformations. in-in time, i.e. chemical speed. r-tions, the mechanisms of these transformations, as well as the dependence of the chemical. process from the conditions of its implementation. She establishes patterns of betrayalchanges in the composition of the transforming system over time, reveals the connection between the rate of chemical. r-tion and external conditions, and also studies factors influencing the speed and direction of chemical reactions. districts.
Most chem. p-tions are complex multi-stage processes consisting of individual elementary chemical acts. transformation, transport of reagents and energy transfer. Theoretical chem. kinetics includes the study of the mechanisms of elementary processes and calculates the rate constants of such processes based on the ideas and apparatus of classical. mechanics and quantum theory, deals with the construction of models of complex chemistry. processes, establishes a connection between the structure of chemicals. compounds and their reactions. ability. Identification of kinetic patterns for complex processes (formal kinetics) are often based on math. modeling and allows you to test hypotheses about the mechanisms of complex processes, as well as establish a system of differentials. equations describing the results of the process under different conditions. ext. conditions.
For chem. kinetics is characterized by the use of many physical. research methods that make it possible to carry out local excitations of reacting molecules, study fast (up to femtosecond) transformations, automate the registration of kinetics. data with their simultaneous processing on a computer, etc. Kinetic accumulation is intensively accumulated. information through kinetic banks constants, incl. for chem. r-tions in extreme conditions.
A very important branch of physical chemistry, closely related to chemistry. kinetics is the study of catalysis, i.e., the change in the speed and direction of chemistry. r-tion when exposed to substances (
