How does physical chemistry differ from chemical physics? Physics and chemistry - how do these sciences differ? Chemistry: what everything is made of

History of physical chemistry

M.V. Lomonosov, which in 1752

N.N. Beketov 1865

AND Nernst.

M. S. Vrevsky.

Molecules, ions, free radicals.

Atoms of elements can form three types of particles involved in chemical processes - molecules, ions and free radicals.

Molecule is the smallest neutral particle of a substance that has its chemical properties and is capable of independent existence. There are monoatomic and polyatomic molecules (diatomic, triatomic, etc.). Under ordinary conditions, noble gases consist of monatomic molecules; molecules of high-molecular compounds, on the contrary, contain many thousands of atoms.

Ion- a charged particle, which is an atom or group of chemically bonded atoms with an excess of electrons (anions) or a deficiency of them (cations). In a substance, positive ions always exist together with negative ones. Since the electrostatic forces acting between ions are large, it is impossible to create in a substance any significant excess of ions of the same sign.

Free radical is called a particle with unsaturated valences, i.e. a particle with unpaired electrons. Such particles are, for example, ·CH 3 and ·NH 2. Under normal conditions, free radicals, as a rule, cannot exist for a long time, since they are extremely reactive and easily react to form inert particles. Thus, two methyl radicals CH3 combine to form a molecule C 2 H 6 (ethane). Many reactions are impossible without the participation of free radicals. At very high temperatures (for example, in the atmosphere of the Sun), the only diatomic particles that can exist are free radicals (·CN, ·OH, ·CH and some others). Many free radicals are present in the flame.

Free radicals of a more complex structure are known, which are relatively stable and can exist under normal conditions, for example, the triphenylmethyl radical (C 6 H 5) 3 C (with its discovery the study of free radicals began). One of the reasons for its stability is spatial factors - the large size of phenyl groups, which prevent the combination of radicals into a hexaphenylethane molecule.

Covalent bond.

Each chemical bond in the structural formulas is represented valence line , For example:

H−H (bond between two hydrogen atoms)

H 3 N−H + (bond between the nitrogen atom of the ammonia molecule and the hydrogen cation)

(K +)−(I−) (bond between potassium cation and iodide ion).

A chemical bond is formed due to attraction of atomic nuclei to a pair of electrons(indicated by dots ··), which is represented in the electronic formulas of complex particles (molecules, complex ions) valence line−, unlike their own, lone pairs of electrons each atom, for example:

:::F−F:::

(F 2);

H−Cl:::

(HCl);

.. H−N−H | H

(NH 3)

The chemical bond is called covalent, if it is formed by sharing a pair of electrons both atoms.

Molecular polarity

Molecules that are formed by atoms of the same element will generally be non-polar , how non-polar the bonds themselves are. Thus, the molecules H 2, F 2, N 2 are non-polar.

Molecules that are formed by atoms of different elements can be polar And non-polar . It depends geometric shape.
If the shape is symmetrical, then the molecule non-polar(BF 3, CH 4, CO 2, SO 3), if asymmetric (due to the presence of lone pairs or unpaired electrons), then the molecule polar(NH 3, H 2 O, SO 2, NO 2).

When one of the side atoms in a symmetrical molecule is replaced by an atom of another element, the geometric shape is also distorted and polarity appears, for example, in the chlorinated methane derivatives CH 3 Cl, CH 2 Cl 2 and CHCl 3 (CH 4 methane molecules are non-polar).

Polarity the asymmetrical shape of the molecule follows from polarity of covalent bonds between atoms of elements with different electronegativity .
As noted above, there is a partial shift of the electron density along the bond axis towards the atom of a more electronegative element, for example:

H δ+ → Cl δ−	B δ+ → F δ−
C δ− ← H δ+	N δ− ← H δ+

(here δ is the partial electric charge on the atoms).

The more electronegativity difference elements, the higher the absolute value of the charge δ and the more polar there will be a covalent bond.

In molecules that are symmetrical in shape (for example, BF 3), the “centers of gravity” of negative (δ−) and positive (δ+) charges coincide, but in asymmetric molecules (for example, NH 3) they do not coincide.
As a result, in asymmetric molecules, electric dipole - unlike charges separated by some distance in space, for example, in a water molecule.

Hydrogen bond.

When studying many substances, the so-called hydrogen bonds . For example, HF molecules in liquid hydrogen fluoride are connected to each other by a hydrogen bond, similarly, H 2 O molecules in liquid water or in an ice crystal, as well as NH 3 and H 2 O molecules are connected to each other in an intermolecular connection - ammonia hydrate NH 3 H 2 O.

Hydrogen bonds unstable and are destroyed quite easily (for example, when ice melts, water boils). However, some additional energy is spent on breaking these bonds, and therefore the melting and boiling points of substances with hydrogen bonds between molecules are significantly higher than those of similar substances, but without hydrogen bonds:

Valence. Donor-acceptor bonds. According to the theory of molecular structure, atoms can form as many covalent bonds as there are orbitals occupied by one electron, but this is not always the case. [In the accepted scheme for filling an AO, the number of the shell is first indicated, then the type of orbital, and then, if there is more than one electron in the orbital, their number (superscript). So, record (2 s) 2 means that on s-orbitals of the second shell contain two electrons.] A carbon atom in the ground state (3 R) has an electronic configuration (1 s) 2 (2s) 2 (2p x)(2 p y), while two orbitals are not filled, i.e. contain one electron each. However, divalent carbon compounds are very rare and are highly reactive. Usually carbon is tetravalent, and this is due to the fact that for its transition to excited 5 S-state (1 s) 2 (2s) (2p x)(2 p y)(2 p z) With four unfilled orbitals, very little energy is needed. Energy costs associated with transition 2 s-electron to free 2 r-orbital, are more than compensated by the energy released during the formation of two additional bonds. For the formation of unfilled AOs, it is necessary that this process be energetically favorable. Nitrogen atom with electron configuration (1 s) 2 (2s) 2 (2p x)(2 p y)(2 p z) does not form pentavalent compounds, since the energy required for the transfer of 2 s-electron for 3 d-orbital to form a pentavalent configuration (1 s) 2 (2s)(2p x)(2 p y)(2 p z)(3 d), is too big. Similarly, boron atoms with the usual configuration (1 s) 2 (2s) 2 (2p) can form trivalent compounds when in an excited state (1 s) 2 (2s)(2p x)(2 p y), which occurs during transition 2 s-electron for 2 r-AO, but does not form pentavalent compounds, since the transition to the excited state (1 s)(2s)(2p x)(2 p y)(2 p z), due to the transfer of one of 1 s-electrons to a higher level requires too much energy. The interaction of atoms with the formation of a bond between them occurs only in the presence of orbitals with close energies, i.e. orbitals with the same principal quantum number. The relevant data for the first 10 elements of the periodic table are summarized below. The valence state of an atom is the state in which it forms chemical bonds, for example state 5 S for tetravalent carbon.

VALENCE STATES AND VALENCES OF THE FIRST TEN ELEMENTS OF THE PERIODIC TABLE
Element	Ground state	Normal valence state	Regular valency
H	(1s)	(1s)
He	(1s) 2	(1s) 2
Li	(1s) 2 (2s)	(1s) 2 (2s)
Be	(1s) 2 (2s) 2	(1s) 2 (2s)(2p)
B	(1s) 2 (2s) 2 (2p)	(1s) 2 (2s)(2p x)(2 p y)
C	(1s) 2 (2s) 2 (2p x)(2 p y)	(1s) 2 (2s)(2p x)(2 p y)(2 p z)
N	(1s) 2 (2s) 2 (2p x)(2 p y)(2 p z)	(1s) 2 (2s) 2 (2p x)(2 p y)(2 p z)
O	(1s) 2 (2s) 2 (2p x) 2 (2 p y)(2 p z)	(1s) 2 (2s) 2 (2p x) 2 (2 p y)(2 p z)
F	(1s) 2 (2s) 2 (2p x) 2 (2 p y) 2 (2 p z)	(1s) 2 (2s) 2 (2p x) 2 (2 p y) 2 (2 p z)
Ne	(1s) 2 (2s) 2 (2p x) 2 (2 p y) 2 (2 p z) 2	(1s) 2 (2s) 2 (2p x) 2 (2 p y) 2 (2 p z) 2

These patterns are manifested in the following examples:

History of physical chemistry

Physical chemistry began in the mid-18th century. The term "Physical Chemistry" belongs to M.V. Lomonosov, which in 1752 year, for the first time I read “A Course of True Physical Chemistry” to students at St. Petersburg University. In this course, he himself gave the following definition of this science: “Physical chemistry is a science that must, on the basis of physical principles and experiments, explain the reason for what happens through chemical operations in complex bodies.”

Then a break of more than a century followed and the next course in physical chemistry was taught by an academician N.N. Beketov at Kharkov University in 1865 year. Following N.N. Beketov began teaching physical chemistry at other universities in Russia. Flavitsky (Kazan 1874), V. Ostwald (university in Tartu 18807), I.A. Kablukov (Moscow University 1886).

The recognition of physical chemistry as an independent science and academic discipline was expressed at the University of Leipzig (Germany) in 1887. The first department of physical chemistry headed by V. Ostwald and the founding of the first scientific journal on physical chemistry there. At the end of the 19th century, the University of Leipzig was a center for the development of physical chemistry, and the leading physical chemists were: W. Ostwald, J. van't Hoff, Arrhenius And Nernst.

The first department of physical chemistry in Russia was opened in 1914 at the Faculty of Physics and Mathematics of St. Petersburg University, where in the fall he began teaching a mandatory course and practical classes in physical chemistry M. S. Vrevsky.

Difference between physical chemistry and chemical physics

Both of these sciences are at the intersection between chemistry and physics; sometimes chemical physics is included in physical chemistry. It is not always possible to draw a clear boundary between these sciences. However, with a reasonable degree of accuracy this difference can be defined as follows:

· physical chemistry considers in total the processes occurring with the simultaneous participation sets particles;

· chemical physics reviews separate particles and the interactions between them, that is, specific atoms and molecules (thus, there is no place in it for the concept of “ideal gas”, which is widely used in physical chemistry).

Lecture 2 The structure of molecules and the nature of chemical bonds. Types of chemical bonds. The concept of electronegativity of an element. Polarization. Dipole moment. Atomic energy of the formation of molecules. Methods for experimental study of the structure of molecules.

Molecular structure(molecular structure), the relative arrangement of atoms in molecules. During chemical reactions, atoms in the molecules of the reactants are rearranged and new compounds are formed. Therefore, one of the fundamental chemical problems is to clarify the arrangement of atoms in the original compounds and the nature of the changes during the formation of other compounds from them.

The first ideas about the structure of molecules were based on an analysis of the chemical behavior of a substance. These ideas became more complex as knowledge about the chemical properties of substances accumulated. The application of the basic laws of chemistry made it possible to determine the number and type of atoms that make up the molecule of a given compound; this information is contained in the chemical formula. Over time, chemists realized that a single chemical formula is not enough to accurately characterize a molecule, since there are isomer molecules that have the same chemical formulas but different properties. This fact led scientists to believe that the atoms in a molecule must have a certain topology, stabilized by the bonds between them. This idea was first expressed in 1858 by the German chemist F. Kekule. According to his ideas, a molecule can be depicted using a structural formula, which indicates not only the atoms themselves, but also the connections between them. Interatomic bonds must also correspond to the spatial arrangement of atoms. The stages of development of ideas about the structure of the methane molecule are shown in Fig. 1. The structure corresponds to modern data G : the molecule has the shape of a regular tetrahedron, with a carbon atom in the center and hydrogen atoms at the vertices.

Such studies, however, did not say anything about the size of the molecules. This information became available only with the development of appropriate physical methods. The most important of these turned out to be X-ray diffraction. From X-ray scattering patterns on crystals, it became possible to determine the exact position of atoms in a crystal, and for molecular crystals it was possible to localize atoms in an individual molecule. Other methods include diffraction of electrons as they pass through gases or vapors and analysis of the rotational spectra of molecules.

All this information gives only a general idea of the structure of the molecule. The nature of chemical bonds allows us to study modern quantum theory. And although the molecular structure cannot yet be calculated with sufficiently high accuracy, all known data on chemical bonds can be explained. The existence of new types of chemical bonds has even been predicted.

... to chat about the general topic of the words “physics” and “chemistry”.

Isn't it surprising that both words are related to bodybuilding? “Physics” means muscles, “chemistry” – well, there’s no need to explain that.

In general, the science of chemistry is, in principle, the same as physics: it is about phenomena occurring in nature. When Galileo threw balls from the Leaning Tower of Pisa, and Newton created his laws, we were talking about a scale commensurate with man - this was and is physics. Conventional physics deals with objects that are made of substances. Chemistry (alchemy) was and is engaged in the transformation of substances into each other - this is the molecular level. It turns out that the difference between physics and chemistry is on the scale of objects? Nevermind! Quantum physics deals with what atoms are made of - this is the submolecular level. Quantum physics deals with objects within the atom, which gives power over atomic energy and poses philosophical questions. It turns out that chemistry is a narrow strip on the scale of physical scales, although clearly delimited by the level of the atomic-molecular structure of a substance.

I think that the bad flat (linear) infinity* does not apply to the surrounding world. Everything is looped or closed into a sphere. The universe is spherical. If we dig further into the structure of elementary particles (quarks and Higgs bosons), then sooner or later the particles found will close in on the maximum scale - with the Universe, that is, sooner or later we will see our Universe from a bird's eye view through a microscope.

Now let's see if scale ranges apply to bodybuilding. It seems so. “Physics” (training with iron and on simulators) deals with iron objects and muscles as solid objects: a scale commensurate with a person. “Chemistry” (like steroids) is, of course, at the molecular level. It remains to figure out what “quantum physics” is in bodybuilding? Apparently, this is motivation, concentration, willpower and so on - that is, the psyche. And the psyche is based not on a molecular basis, but on certain electric fields and states - their scale is below the atomic. So bodybuilding has reached the full scale...

Reading the article by Ph.D. Elena Gorokhovskaya(“Novaya Gazeta”, No. 55, 05/24/2013, p. 12 or on the “Postnauka” website) about the basics of biosemiotics:

What is living? (...) The main “watershed” is between reductionist** and anti-reductionist approaches. Reductionists argue that life in all its specificities can be explained using physical and chemical processes. Anti-reductionist approaches argue that everything cannot be reduced to physics and chemistry. The most difficult thing is to understand the integrity and purposeful structure of a living organism, where everything is interconnected and everything is aimed at supporting its vital activity, reproduction and development. In the course of individual development, and indeed every moment in the body, something changes, while the natural course of these changes is ensured. It is often said that living organisms should be called processes rather than objects.
...In the twentieth century, cybernetics became important for understanding the specifics of living things, since it rehabilitated the concept of purpose in biology. In addition, cybernetics has made very popular the idea of living organisms as information systems. Thus, humanitarian concepts that were not directly related to material organization were actually introduced into the science of living things.
In the 1960s, a new direction arose in understanding the specifics of living things and in the study of biological systems - biosemiotics, which considers life and living organisms as sign processes and relationships. We can say that living organisms live not in a world of things, but in a world of meanings.
...Molecular genetics was formed to a large extent due to the inclusion of such concepts as “genetic information” and “genetic code” in its conceptual scheme. Talking about the discovery of the genetic code, the famous biologist Martinas Ichas wrote: “The most difficult thing about the “code problem” was to understand that the code exists. It took a century."
Although protein biosynthesis occurs in the cell through a variety of chemical reactions, there is no direct chemical connection between the structure of proteins and the structure of nucleic acids. This connection in its essence is not chemical, but informational, semiotic in nature. The nucleotide sequences in DNA and RNA nucleic acids provide information about the structure of proteins (about the amino acid sequences in them) only because there is a “reader” (aka “writer”) in the cell - in this case, a complex protein biosynthesis system that owns the “genetic tongue." (...) Thus, even at the most fundamental level, the living turns out to be communication, text and “speech”. In each cell and in the body as a whole, reading, writing, rewriting, creating new texts and constant “conversation” in the language of the genetic code of macromolecules and their interactions constantly occur.

* * *

Let's replace a few words in phrases from the first and last paragraphs:

Retrogrades argue that bodybuilding in all its specifics can be reduced to physical training and chemical influences. The progressive approach argues that everything cannot be reduced to “physics” and “chemistry.” Although the growth of muscle mass is carried out through a variety of physical exercises and chemical (at least food) influences, there is no direct connection between muscle growth and the amount of exercise and the amount of “chemistry”. This connection in its essence is not physical or chemical, but informational, semiotic in nature. So even at the most fundamental level bodybuilding turns out to be communication, text and “speech”(we are, of course, not talking about vulgar chatter between approaches). Therefore we can say that bodybuilders should be called not objects, but information processes.

Who would argue that you can’t pump up a muscle foolishly. You need a properly constructed and executed workout, you need proper nutrition, that is, information is required. And if we foolishly stuff ourselves with chemistry, we will get an ambiguous result, if we get one at all. You need a correctly constructed and executed course, that is, again, information is required. The most difficult thing about the problem of such information is to understand that it actually exists. And having realized this, we must learn to isolate it from that muddy pseudo-information ocean that rolls onto the shore of our brain in heavy waves, occasionally throwing out pearl shells from its depths.

True, to open the shells you need an oyster knife...

------------
* bad infinity– a metaphysical understanding of the infinity of the world, which presupposes the assumption of a monotonous, endlessly repeating alternation of the same specific properties, processes and laws of motion on any scale of space and time, without any limit. In relation to the structure of matter, it means the assumption of unlimited divisibility of matter, in which each smaller particle has the same properties and is subject to the same specific laws of motion as macroscopic bodies. The term was introduced by Hegel, who, however, considered true infinity to be a property of absolute spirit, but not matter.
** reductionist approach– from Latin reductio – return, restoration; in this case, reducing the phenomena of life to something else.

Physical chemistry

"An Introduction to True Physical Chemistry". Manuscript by M. V. Lomonosov. 1752

Physical chemistry(often abbreviated in literature as physical chemistry) - a branch of chemistry, the science of the general laws of structure, structure and transformation of chemical substances. Explores chemical phenomena using theoretical and experimental methods of physics.

· 1History of physical chemistry

· 2 Subject of study of physical chemistry

· 3Difference between physical chemistry and chemical physics

· 4 Sections of physical chemistry

o 4.1 Colloidal chemistry

o 4.2 Crystal chemistry

o 4.3 Radiochemistry

o 4.4Thermochemistry

o 4.5 The doctrine of the structure of the atom

o 4.6 The doctrine of corrosion of metals

o 4.7 The doctrine of solutions

o 4.8 Chemical kinetics

o 4.9 Photochemistry

o 4.10Chemical thermodynamics

o 4.11 Physico-chemical analysis

o 4.12 Theory of reactivity of chemical compounds

o 4.13 High energy chemistry

o 4.14 Laser chemistry

o 4.15 Radiation chemistry

o 4.16 Nuclear chemistry

o 4.17Electrochemistry

o 4.18 Sound chemistry

o 4.19 Structural chemistry

· 5 Potentiometry

History of physical chemistry[

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 in 1752 first taught the “Course of True Physical Chemistry” to students at 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 for the publication of 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 study of the structure of matter, including: the structure of molecules, chemical thermodynamics, chemical kinetics and catalysis. 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 as separate sections in physical chemistry. physical chemistry and are sometimes considered as independent sections of 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

· physical chemistry considers in total the processes occurring with the simultaneous participation sets particles;

· chemical physics reviews separate particles and the interaction between them, that is, specific atoms and molecules (thus, there is no place in it for the concept of “ideal gas”, which is widely used in physical chemistry).

Physics and chemistry are sciences that directly contribute to technological progress in the 21st century. Both disciplines study the laws of functioning of the surrounding world, changes in the smallest particles of which it consists. All natural phenomena have a chemical or physical basis, this applies to everything: glow, combustion, boiling, melting, any interaction of something with something.
Everyone at school studied the basics of chemistry and physics, biology and natural science, but not everyone connected their life with these sciences, not everyone can determine the line between them now.

To understand what the main differences between physical science and chemical science are, you must first take a closer look at them and become familiar with the basic principles of these disciplines.

About physics: motion and its laws

Physics deals direct study of the general properties of the surrounding world, simple and complex forms of movement of matter, natural phenomena that underlie all these processes. Science studies the qualities of various material objects and the manifestations of interactions between them. Physicists are also looking at general patterns for different types of matter; these unifying principles are called physical laws.

Physics is in many ways a fundamental discipline because it considers material systems at different scales most broadly. It is in very close contact with all natural sciences; the laws of physics determine both biological and geological phenomena to the same extent. There is a strong connection with mathematics, since all physical theories are formulated in the form of numbers and mathematical expressions. Roughly speaking, the discipline broadly studies absolutely all phenomena of the surrounding world and the patterns of their occurrence, based on the laws of physics.

Chemistry: what does everything consist of?

Chemistry primarily deals with the study of properties and substances in combination with their various changes. Chemical reactions are the results of mixing pure substances and creating new elements.

Science closely interacts with other natural disciplines such as biology and astronomy. Chemistry studies the internal composition of different types of matter, aspects of the interaction and transformation of the constituents of matter. Chemistry also uses its own laws and theories, regularities, and scientific hypotheses.

What are the main differences between physics and chemistry?

Belonging to natural science unites these sciences in many ways, but there are many more differences between them than there are in common:

The main difference between the two natural sciences is that physics studies elementary particles (microworld, this includes the atomic and nucleon levels) and various properties of substances in a certain state of aggregation. Chemistry is engaged in the study of the very processes of “assembly” of molecules from atoms, the ability of a substance to enter into certain reactions with a substance of another kind.
Like biology and astronomy, modern physics allows for many non-rational concepts in its methodological tools, this mainly concerns theories of the origin of life on Earth, the origin of the Universe, and connections with philosophy in considering the concepts of the primary cause of the “ideal” and “material.” Chemistry remained much closer to the rational foundations of the exact sciences, moving away both from ancient alchemy and from philosophy in general.
The chemical composition of bodies in physical phenomena remains unchanged, as do their properties. Chemical phenomena involve the transformation of a substance into another with the appearance of its new properties; This is the difference between the subjects studied by these disciplines.
A wide class of phenomena described by physics. Chemistry is much more highly specialized discipline, it is focused on studying only the microworld (molecular level), as opposed to physics (macroworld and microworld).
Physics deals with the study of material objects with their qualities and properties, and chemistry works with the composition of these objects, the smallest particles of which they are composed and which interact with each other.