Chemistry in the modern scientific picture of the world. Topic: Science Test

Chemistry– the science of transformations of substances, accompanied by changes in their composition and structure.

Phenomena in which other substances are formed from one substance are called chemical. Naturally, on the one hand, in these phenomena can be detected purely physical changes, and, on the other hand, chemical phenomena are always present in all biological processes. Thus, it is obvious connection chemistry with physics and biology.

This connection, apparently, was one of the reasons why chemistry could not become an independent science for a long time. Although already Aristotle divided substances into simple and complex, pure and mixed, and tried to explain the possibility of some transformations and the impossibility of others, chemical he considered the phenomenon as a whole quality changes and therefore attributed to one of the genera movement. Chemistry Aristotle was part of him physicists– knowledge about nature ().

Another reason for the lack of independence of ancient chemistry is associated with theoreticality, the contemplation of all ancient Greek science as a whole. They looked for the unchangeable in things and phenomena - idea. Theory chemical phenomena led to element idea() as a certain beginning of nature or to idea of ​​the atom as an indivisible particle of matter. According to the atomistic concept, the peculiarities of the shapes of atoms in their many combinations determine the diversity of qualities of the bodies of the macrocosm.

Empirical experience belonged in Ancient Greece to the area arts And crafts. It also included practical knowledge about chemical processes: smelting metals from ores, dyeing fabrics, tanning leather.

Probably, from these ancient crafts, known back in Egypt and Babylon, the “secret” hermetic art of the Middle Ages arose - alchemy, most widespread in Europe in the 9th-16th centuries.

Originating in Egypt in the 3rd-4th centuries, this area of ​​practical chemistry was associated with magic and astrology. Its goal was to develop ways and means of transforming less noble substances into more noble ones in order to achieve real perfection, both material and spiritual. During the search universal By means of such transformations, Arab and European alchemists obtained many new and valuable products, and also improved laboratory technology.

1. The period of the birth of scientific chemistry(XVII - late XVIII century; Paracelsus, Boyle, Cavendish, Stahl, Lavoisier, Lomonosov). It is characterized by the fact that chemistry stands out from natural science as an independent science. Its goals are determined by the development of industry in modern times. However, theories of this period, as a rule, use either ancient or alchemical ideas about chemical phenomena. The period ended with the discovery of the law of conservation of mass in chemical reactions.

For example, iatrochemistry Paracelsus (XVI century) was devoted to the preparation of medicines and the treatment of diseases. Paracelsus explained the causes of disease by disruption of chemical processes in the body. Like the alchemists, he reduced the variety of substances to several elements - carriers of the basic properties of matter. Consequently, restoring their normal ratio by taking medications cures the disease.

Theory phlogiston Stahl (XVII-XVIII centuries) generalized many chemical oxidation reactions associated with combustion. Stahl suggested the existence of the element “phlogiston” in all substances - the beginning of flammability.

Then the combustion reaction looks like this: combustible body → residue + phlogiston; the reverse process is also possible: if the residue is saturated with phlogiston, i.e. mixed, for example, with coal, you can again get metal.

2. The period of discovery of the basic laws of chemistry(1800-1860; Dalton, Avogadro, Berzelius). The result of the period was the atomic-molecular theory:

a) all substances consist of molecules that are in continuous chaotic motion;

b) all molecules consist of atoms;

3. Modern period(started in 1860; Butlerov, Mendeleev, Arrhenius, Kekule, Semenov). It is characterized by the separation of branches of chemistry as independent sciences, as well as the development of related disciplines, for example, biochemistry. During this period, the periodic system of elements, theories of valence, aromatic compounds, electrochemical dissociation, stereochemistry, and the electronic theory of matter were proposed.

The modern chemical picture of the world looks like this:

1. Substances in the gaseous state consist of molecules. In the solid and liquid states, only substances with a molecular crystal lattice (CO 2, H 2 O) consist of molecules. Most solids have either an atomic or ionic structure and exist in the form of macroscopic bodies (NaCl, CaO, S).

2. A chemical element is a certain type of atom with the same nuclear charge. The chemical properties of an element are determined by the structure of its atom.

3. Simple substances are formed from atoms of one element (N 2, Fe). Complex substances or chemical compounds are formed by atoms of different elements (CuO, H 2 O).

4. Chemical phenomena or reactions are processes in which some substances are transformed into others in structure and properties without changing the composition of the nuclei of atoms.

5. The mass of substances entering into a reaction is equal to the mass of substances formed as a result of the reaction (law of conservation of mass).

6. Any pure substance, regardless of the method of preparation, always has a constant qualitative and quantitative composition (the law of constancy of composition).

The main task chemistry– obtaining substances with predetermined properties and identifying ways to control the properties of the substance.

Chemistry– the science of substances and their transformations, which are accompanied by changes in the composition and structure of the substance. These processes take place on the border between the micro and macro worlds.

Chemistry began to develop as an independent science from the middle of the 17th century. The scientific stage of development of chemistry was preceded by the period of alchemy. This cultural phenomenon is associated with attempts to obtain “perfect” metals - gold and silver - from “imperfect” metals using a hypothetical substance - the “philosopher’s stone” or elixir. Despite the obvious impossibility of carrying out this transformation, alchemy stimulated the development of chemical technologies (metallurgy, glassmaking, production of ceramics, paper, alcoholic beverages) and the discovery of ways to obtain new chemicals.

The scientific stage of development of chemistry is usually divided into four periods, in each of which a conceptual knowledge system is formed:

a) the doctrine of the composition of matter(mid 17th – mid 18th centuries) – studies the dependence of the properties of substances on the chemical composition (composition of the molecule);

b) the study of the structure of matter (structural chemistry)(mid 18th – mid 20th centuries) – studies the dependence of the properties of substances on the structure of the molecule;

c) the study of chemical processes(mid-20th century) – the mechanisms of chemical reactions, as well as the processes of their acceleration (catalysis), are studied;

d) evolutionary chemistry(last 25-30 years) - studies chemical processes in living nature, processes of self-organization of chemical systems.

3.1.1 The doctrine of the composition of matter

Classical chemistry is based on the concept of atomism, which was formulated in ancient philosophy by Leucipus, Democritus and Epicurus. On the basis of atomism, in the mid-19th century the basic principles of atomic-molecular teaching were formulated.

Substances are made up of molecules. A molecule is the smallest particle of a substance that has its chemical properties. Molecules differ in composition, size, physical and chemical properties.

Molecules are in continuous motion; there is mutual attraction and repulsion between them. The speed of movement of molecules depends on the state of aggregation of substances.

During physical phenomena, the composition of molecules remains unchanged, but during chemical reactions, others are formed from some molecules.

Molecules are made up of atoms. The properties of atoms of one element differ from the properties of atoms of other elements. Atoms are characterized by certain sizes and masses. The mass of an atom expressed in atomic mass units (amu) is called relative atomic mass.

1 amu = 1.667 10 -27 kg.

Atomic-molecular science made it possible to explain the basic concepts and laws of chemistry. The concept of “chemical element” was proposed by R. Boyle, and the designation of chemical elements by symbols was proposed in 1814 by J. Berzelius. X imical element- a certain type of atom with the same nuclear charge. The charge of the nucleus is numerically equal to the atomic number of the element in the periodic table. Currently, 118 chemical elements are known, of which 94 are found in nature, the remaining 24 are obtained artificially as a result of nuclear reactions.

Atom- the smallest particle of a chemical element that retains all its chemical properties. The chemical properties of an element are determined by the structure of its atom. This leads to a definition of an atom that corresponds to modern concepts: Atom is an electrically neutral particle consisting of a positively charged atomic nucleus and negatively charged electrons.

Isotopes- atoms of the same chemical element that have different masses and, accordingly, different numbers of neutrons in the nucleus. Isotopes can be stable, i.e. their nuclei are not subject to spontaneous decay, and are radioactive, which are capable of transforming into atoms of other elements until a stable isotope is formed (Uranium-238 Lead-206).

Allotropy– the ability of elements to exist in the form of various simple substances that differ in physical and chemical properties. Allotropy can result from the formation of molecules with different numbers of atoms (for example, atomic oxygen O, molecular oxygen O 2 and ozone O 3) or the formation of different crystalline forms (for example, graphite and diamond). As a result of allotropy, about 400 simple substances are formed from 118 elements.

Molecule - it is the smallest particle of a given substance that has its chemical properties. The concept of molecule was introduced by the Italian scientist A. Avogadro. In 1811, he proposed a molecular theory of the structure of matter.

The chemical properties of a molecule are determined by its composition and chemical structure. The sizes of molecules are determined by their mass and structure, and for large molecules they can reach 10 -5 cm. Currently, over 18 million types of molecules of different substances are known.

A chemical formula is a conventional recording of the composition of a substance using chemical symbols and indices. The chemical formula shows which atoms of which elements and in what ratio are connected to each other in a molecule.

Basic chimic laws.

Law of conservation of mass(M.V. Lomonosov, A.L. Lavoisier): the mass of substances that entered into the reaction is equal to the mass of substances formed as a result of the reaction. From the point of view of atomic-molecular science, as a result of chemical reactions, atoms do not disappear or appear, but they are rearranged (chemical transformation). Since the number of atoms before and after the reaction remains unchanged, their total mass should also not change. Based on the law of conservation of mass, it is possible to draw up equations of chemical reactions and make calculations using them. This law is the basis of quantitative chemical analysis.

At the beginning of the 20th century, the formulation of the law of conservation of mass was revised in connection with the advent of the theory of relativity (see section 2.4.1), according to which the mass of a body depends on its speed and, therefore, characterizes not only the amount of matter, but also its movement. Energy received by the body E is associated with an increase in its mass m by the ratio E= m c 2, where c is the speed of light. This ratio is not used in chemical reactions, because 1 kJ of energy corresponds to a change in mass of approximately 10 -11 g and m practically cannot be measured. However, in nuclear reactions, where the change in energy E is millions of times greater than in chemical reactions, m should be taken into account.

Law of constancy of the composition of matter:

According to the law of constancy of composition, any chemically pure substance has a constant qualitative and quantitative composition, regardless of the method of its preparation. The qualitative and quantitative composition of a substance is shown by its chemical formula. For example, no matter how the substance water (H 2 O) is obtained, it has a constant composition: two hydrogen atoms and one oxygen atom.

From the law of constancy of composition it follows that during the formation of a complex substance, elements combine with each other in certain mass ratios.

It has now been established that this law is always valid for compounds with a molecular structure. The composition of compounds with a non-molecular structure (with an atomic, ionic and metal crystal lattice) is not constant and depends on the conditions of preparation.

Law of multiple ratios (J. Dalton)- if two elements form several chemical compounds with each other, then the masses of the elements are related to each other as small integers.

For example: in nitrogen oxides N2O, N2O3, NO2 (N2O4), N2O5, the number of oxygen atoms per two nitrogen atoms is related as 1: 3: 4: 5.

Law of volumetric relations (Gay-Lussac) - the volumes of gases entering into chemical reactions and the volumes of gases formed as a result of the reaction are related to each other as small integers. Consequently, the stoichiometric coefficients in the equations of chemical reactions for molecules of gaseous substances indicate in what volume ratios gaseous substances react or are obtained. For example:

2CO+O 2
2CO 2

When two volumes of carbon (II) oxide are oxidized by one volume of oxygen, 2 volumes of carbon dioxide are formed, i.e. the volume of the initial reaction mixture is reduced by 1 volume.

Avogadro's law- equal volumes of any gases taken at the same temperature and at the same pressure contain the same number of molecules. According to this law:

the same number of molecules of different gases under the same conditions occupies the same volumes;

1 mole of any ideal gas under normal conditions (0°C = 273°K, 1 atm = 101.3 kPa) occupies the same volume of 22.4 liters.

French chemist A.L. Lavoisier was the first to try to systematize chemical elements according to their mass. The English chemist J. Dalton introduced the concept of atomic mass and was the creator of the theory of atomic structure. In 1804, he proposed a table of the relative atomic masses of hydrogen, nitrogen, carbon, sulfur and phosphorus, taking the atomic mass of hydrogen as one. Currently, atomic mass is measured relative to 1/12 the mass of an atom of the carbon isotope.

The work on studying the properties of atoms was continued by D.I. Mendeleev formulated the periodic law in 1869 and developed the Periodic Table of Chemical Elements. The periodic law was formulated as follows: “The properties of simple bodies, as well as the forms and properties of compounds of elements, are periodically dependent on the atomic weights of the elements.” D.I. Mendeleev used as a system-forming factor mass of a chemical element. In the Periodic System D.I. Mendeleev had 62 elements.

Quantum mechanics clarified that the properties of chemical elements and their compounds are determined by the charge of the atomic nucleus. Modern formulation of the periodic law of chemical elements: the properties of simple substances, as well as the forms and properties of compounds of elements, periodically depend on the magnitude of the charge of the atomic nucleus and are determined by periodically repeating similar electronic configurations of their atoms.

The reactivity of an atom of a chemical element is determined by the number of electrons in the outer shell of the atom.

Valence– properties of atoms of one element to form a certain number of bonds with atoms of other elements. Chemical bonds between atoms are carried out by electrons located on the outer shell and less tightly bound to the nucleus. They were called valence electrons. Valence (the number of valence electrons) can be determined using D.I. Mendeleev’s table, knowing the number of the group in which the chemical element is located.

Electronegativity– the property of an atom in a compound to attract valence electrons. The more an atom attracts electrons toward itself, the greater its electronegativity. Oxidation state- a conditional charge that is formed on an atom, taking into account that when a bond is formed, the electron goes completely to a more electronegative atom. The maximum oxidation state of an element is determined by the group number in the periodic table.

Atoms in molecules are interconnected by chemical bonds, which are formed due to the redistribution of valence electrons between atoms. When a chemical bond is formed, atoms tend to acquire a stable (complete) outer electron shell. Chemical bonding is a type of fundamental electromagnetic interaction. The formation of a chemical bond occurs due to the attraction of positive and negative charges that are formed on an atom when its electron is lost or displaced from a stationary orbit. Depending on the nature of the interaction of atoms, covalent, ionic, metallic and hydrogen chemical bonds are distinguished.

Covalent bond carried out due to the formation of shared electron pairs between two atoms. It can be polar and non-polar. Ionic bond is an electrostatic attraction between ions that are formed due to the complete displacement of an electron pair to one of the atoms. Metal connection - it is the connection between positive metal ions through a common electron cloud ("electron gas").

In addition to intramolecular bonds, intermolecular bonds are also formed. Intermolecular interactions are interactions between molecules that do not lead to the rupture or formation of intramolecular chemical bonds. The state of aggregation of a substance, structural, thermodynamic, thermophysical and other properties of substances depend on intermolecular interactions. An example of an intermolecular bond is a hydrogen bond.

A hydrogen bond is an intermolecular bond formed by the attraction of a more electronegative atom (F, O, N) and a hydrogen atom with a partial positive charge. For example, hydrogen bonds occur between molecules of water, alcohol, and organic acids. It affects the boiling point of a substance.

Hydrogen bonds can also form inside molecules. For example, intramolecular hydrogen bonds exist in molecules of nucleic acids, proteins, polypeptides, etc. and determine the structure of these macromolecules

The development of chemical knowledge is stimulated by the need for man to obtain various substances for his life. Nowadays, chemical science makes it possible to obtain substances with given properties and to find ways to control these properties, which is the main problem of chemistry and the system-forming beginning of it as a science.

Chemistry usually seen as a science that studies the properties and transformations of substances, accompanied by changes in their composition and structure. She studies the nature and properties of various chemical bonds, the energy of chemical reactions, the reactivity of substances, the properties of catalysts, etc.

The term " chemistry"comes, according to Plutarch, from one of the ancient names of Egypt, Hemi(“black earth”) It was in Egypt, long before our era, that metallurgy, ceramics, glass making, dyeing, perfumery, cosmetics, etc. achieved significant development. There is another point of view associated with the Greek hymia - the art of casting (from hyma - casting).

In the Arab East the term “ alchemy" The alchemists' main goal was to create a "philosopher's stone" capable of transforming all metals into gold. This was based on a practical order: gold in Europe was necessary for the development of trade, and there were few known deposits. Alchemists have accumulated vast practical experience in the transformation of substances, developed appropriate tools, techniques, chemical utensils, etc.

Concerning chemistry, then, despite the diversity of empirical material, in this science until the discovery in 1869 of the periodic table of chemical elements D.I.Mendeleev(1834 – 1907), essentially there was no unifying concept, with the help of which it would be possible to explain all the accumulated factual material. Consequently, it was impossible to represent all existing knowledge as theoretical system chemistry.

It would, however, be wrong not to take into account the enormous research work that led to the establishment of a systematic view of chemical knowledge. If we turn to the fundamental theoretical generalizations of chemistry, we can distinguish four conceptual levels.

From the very first steps, chemists intuitively and empirically understood that properties simple substances and chemical compounds depend on those unchanged beginnings, which later became known as elements. The identification and analysis of these elements, the discovery of the connection between them and the properties of substances covers a significant period in the history of chemistry. This first conceptual level can be called the study of the composition of substances. At this level, the study of various properties and transformations of substances took place depending on their chemical composition, determined by their elements. A striking analogy with the concept is obvious atomism in physics. Chemists, like physicists, were looking for that original basis with the help of which they tried to explain the properties of all simple and complex substances. This concept was formulated quite late - in 1860, at the first International Congress of Chemists in Karlsruhe in Germany. Chemical scientists assumed that:

· all substances consist of molecules that are in continuous and spontaneous movement;

All molecules are made up of atoms;

· atoms and molecules are in continuous motion;

Second conceptual level cognition is associated with structure research, that is, the method of interaction of elements in the composition of substances and their compounds. It was found that the properties of substances obtained as a result of chemical reactions depend not only on the elements, but also on relationships and interactions these elements during the reaction process. Thus, diamond and coal have different properties precisely because of their different structures, although their chemical composition is the same.

Third conceptual level knowledge is research internal mechanisms and conditions for the occurrence of chemical processes, such as temperature, pressure, reaction rate and some others. All these factors have a huge impact on the nature of the processes and the volume of substances produced, which is of paramount importance for mass production.

Fourth conceptual level– level of evolutionary chemistry – is a further development of the previous level, associated with a more in-depth study of the nature of the reagents involved in chemical reactions, as well as the use of catalysts that significantly accelerate the rate of their occurrence. At this level it is comprehended the process of the origin of living matter from inert matter.

2. The doctrine of the composition of matter.

At this level, the issues of determining a chemical element, a chemical compound and obtaining new materials based on the wider use of chemical elements were resolved.

The first scientific definition of a chemical element as a “simple body” was formulated in the 17th century. English chemist and physicist R. Boyle. But at that time it was not yet open none of them. The chemical element phosphorus was the first to be discovered in 1669, then cobalt, nickel and others.

				4. Evolutionary chemistry
			3. The doctrine of chemical processes
		2. Structural chemistry
	1. The doctrine of composition
	1660s	1800s	1950s	1970s	Present tense

Rice. 1. Basic concepts of chemical science.

But even in the 18th century, scientists considered iron, copper and other metals known at that time as complex bodies, and the scale resulting from heating them as a simple body. But scale is a metal oxide, a complex body.

The misconception that existed in the 18th century was associated with the false hypothesis of phlogiston by a German physician and chemist Georg Stahl(1660 – 1734). He believed that metals consist of scale and phlogiston(from the Greek flogizein - to ignite, burn), a special weightless substance that, when heated, evaporates and remains a pure element. In his opinion, the composition of beeswax and coal mainly includes phlogiston, which evaporates during combustion and, as a result, only a little ash remains.

Discovery by a French chemist A. L. Lavoisier oxygen and the establishment of its role in the formation of various chemical compounds made it possible to abandon previous ideas about phlogiston. Lavoisier for the first time systematized chemical elements based on those available in the 18th century. knowledge. Gradually, chemists discovered more and more new chemical elements, described their properties and reactivity, and thanks to this accumulated a huge amount of empirical material that needed to be brought into a certain system. Such systems were proposed by various scientists, but they were very imperfect because insignificant, minor and even clean external signs of elements.

Great merit D. I. Mendeleev is that, having opened in 1869 periodic law, he laid the foundation for the construction of a truly scientific system of chemical elements. He chose as a system-forming factor atomic weight. In accordance with atomic weight, he arranged the chemical elements into a system and showed that their properties depend periodically on the value of the atomic weight. Before Mendeleev's systematic approach, chemistry textbooks were very cumbersome. Thus, the chemistry textbook by L.Zh. Tenara consisted of 7 volumes of 1000 - 1200 pages each.

The periodic law of D.I. Mendeleev is formulated as follows: “The properties of simple bodies, as well as the forms and properties of compounds of elements, are periodically dependent on the atomic weights of the elements.”

This generalization gave new ideas about the elements, but due to the fact that the structure of the atom was not yet known, its physical meaning was inaccessible. In the modern view, this periodic law looks like this: “The properties of simple substances, as well as the forms and properties of compounds of elements, are periodically dependent on the magnitude of the charge of the atomic nucleus (ordinal number).” For example, the element chlorine has two isotope, differing from each other in atomic mass. But both of them belong to the same chemical element - chlorine due to the same charge of their nuclei. Atomic weight is the arithmetic mean of the masses of the isotopes that make up an element.

In the Periodic System D.I. Mendeleev had 62 elements, in the 1930s. it ended in uranium (Z = 92). In 1999, it was reported that element 114 had been discovered through physical synthesis of atomic nuclei.

For a long time, it seemed obvious to chemists what exactly belongs to chemical compounds, and what about simple bodies or mixtures. However, the recent use of physical methods for studying matter has made it possible to identify physical nature of chemistry, those. those internal forces that unite atoms into molecules that represent a strong quantum mechanical integrity. These forces turned out to be chemical bonds.

Chemical bond is an interaction that binds individual atoms into more complex formations, into molecules, ions, crystals, i.e. into those structural levels of organization of matter that chemical science studies. Chemical bonds represent electron exchange interaction with the appropriate characteristics. We are talking, first of all, about electrons located on the outer shell and less tightly bound to the nucleus. They were called valence electrons. Depending on the nature of the interaction between these electrons, types of bonds are distinguished.

Covalent bond is carried out due to the formation of electron pairs that belong equally to both atoms.

Ionic bond is an electrostatic attraction between ions formed by the complete displacement of an electrical pair towards one of the atoms, for example, NaCl.

Metal connection - This is a bond between positive ions in crystals of metal atoms, formed due to the attraction of electrons, but moving around the crystal in a free form.

Further development of science made it possible to clarify that the properties of chemical elements depend on the charge of the nucleus of atoms, which is determined by the number of protons or electrons, respectively. Currently chemical element call a collection of atoms with a specific nuclear charge Z, although they differ in their mass, as a result of which the atomic weights of elements are not always expressed in whole numbers.

Simple substance is the form of existence of a chemical element in a free state. However, for example, even gaseous (not to mention the liquid and solid state of aggregation) hydrogen exists in two varieties, differing in the magnetic orientation of the H nuclei - orthohydrogen and parahydrogen. They differ, for example, in heat capacity. There are also two types of gaseous and four types of liquid oxygen. Therefore, there are St. simple substances. 500, while chemical elements are just over a hundred.

The problem of chemical compounds is also solved from the standpoint of atomism. What is considered a mixture and what is a chemical compound? Does such a compound have a constant or variable composition?

French chemist Joseph Proust(1754 – 1826) believed that any chemical compound must have a completely definite, unchanging composition: “...nature gave a chemical compound a constant composition and thereby placed it in a completely special position compared to a solution, an alloy and a mixture.” Moreover, the composition of a chemical compound does not depend on the method of its preparation.

Subsequently, the law of constancy of composition was substantiated from the standpoint of atomic-molecular theory by an outstanding English chemist John Dalton(1766 – 1844). He introduced the concept of “atomic weight” into science and argued that every substance, simple or complex, consists of tiny particles - molecules, which in turn are formed from atoms. Exactly molecules are the smallest particles that have the properties of matter.

For a long time, the law of constancy of chemical composition formulated by Proust was considered an absolute truth, although another French chemist Claude Berthollet(1748 – 18232) pointed to the existence of compounds of variable composition in the form of solutions and alloys. Subsequently, more convincing evidence was found for the existence of chemical compounds of variable composition in the school of the famous Russian physical chemist Nikolai Semenovich Kurnakov(1860 – 1940). In honor of K. Berthollet, he named them Berthollides. He included among them those compounds whose composition depends on how you get them. For example, compounds of two metals such as manganese and copper, magnesium and silver and others are characterized by variable composition, but they constitute single chemical compounds. Over time, chemists discovered other compounds of the same variable composition and came to the conclusion that they differ from compounds of constant composition in that they do not have a specific molecular structure.

Since it turned out that the nature of the compound, that is, the nature of the connection of atoms in its molecule depends on their chemical bonds, then the idea of ​​the molecule expanded. A molecule is still called the smallest particle of a substance that determines its properties and can exist independently. However, molecules now also include a variety of other quantum mechanical systems (ionic, atomic single crystals, polymers arising from hydrogen bonds, and other macromolecules). In them, the chemical bond is carried out not only through interaction external, valence electrons, but also ions, radicals and other components. They have a molecular structure, although they are not in a strictly constant composition.

Thus, the sharp former opposition between chemical compounds of constant composition, which have a specific molecular structure, and compounds of variable composition, devoid of this specificity, is now disappearing. The identification of a chemical compound with a molecule consisting of several different atoms of chemical elements also loses its force. In principle, a molecule of a compound can consist of two or more atoms of one element: these are molecules H 2, O 2, graphite, diamond and other crystals.

Nowadays there is information about 8 million individual chemical compounds of constant and billions of variable composition.

Within the framework of the study of the composition and structure of elements, an important place is occupied by the problem of producing new materials. We are talking about the inclusion of new chemical elements in their composition. The fact is that 98.7% of the mass of the layer of the Earth on which man carries out his production activities consists of eight chemical elements: 47.0% - oxygen, 27.5% - silicon, 8.8% - aluminum, 4.6 % - iron, 3.6% - calcium, 2.6% - sodium, 2.5% - potassium, 2.1% - magnesium. However, these chemical elements are distributed unevenly on Earth and are also unevenly used. More than 95% of metal products contain iron at their core. Such consumption leads to iron deficiency. Therefore, the task is to use other chemical elements for human activity that can replace iron, in particular, the most common silicon. Silicates, various compounds of silicon with oxygen and other elements make up 97% of the mass of the earth's crust.

Based on modern advances in chemistry, it has become possible to replace metals with ceramics not only as a more economical product, but in many cases as a more suitable structural material compared to metal. The lower density of ceramics (40%) makes it possible to reduce the weight of objects made from it. The inclusion of new chemical elements in the production of ceramics: titanium, boron, chromium, tungsten and others makes it possible to obtain materials with predetermined special properties (fire resistance, heat resistance, high hardness, etc.).

In the second half of the 20th century. more and more new chemical elements began to be used in synthesis organoelement compounds from aluminum to fluorine. Some of these compounds serve as chemical reagents for laboratory research, and others serve for the synthesis of new materials.

About 10 years ago there were more 1 million varieties products produced by the chemical industry. Now in the chemical laboratories of our planet daily 200–250 new chemical compounds are synthesized.

3. Level of structural chemistry.

Structural chemistry represents the level of development of chemical knowledge at which the concept of “structure” dominates, i.e. structure of a molecule, macromolecule, single crystal.

With the emergence of structural chemistry, chemical science now has previously unknown possibilities for targeted qualitative influence on the transformation of matter. Famous German chemist Friedrich Kekule(1829 – 1896) began to connect structure with the concept of valence of an element. It is known that chemical elements have a certain valence(from Latin valentia - strength, ability) - the ability to form compounds with other elements. Valency determines how many atoms an atom of a given element can combine with. Back in 1857 F. Kekule showed that carbon is tetravalent, and this makes it possible to attach up to four elements of monovalent hydrogen to it. Nitrogen can add up to three monovalent elements, oxygen - up to two.

This Kekule scheme led researchers to understand the mechanism for obtaining new chemical compounds. A. M. Butlerov noticed that in such compounds plays an important role energy, with which substances communicate with each other. This interpretation of Butlerov was confirmed by research in quantum mechanics. Thus, the study of the structure of a molecule is inextricably linked with quantum mechanical calculations.

Based on ideas about valence, those structural formulas, which are used in the study of chemistry, especially organic. By combining atoms of various chemical elements according to their valence, it is possible to predict the production of various chemical compounds depending on the starting reagents. This way it could be controlled synthesis process various substances with given properties, and this is precisely the most important task of chemical science.

In the 60s - 80s. XIX century the term appeared "organic synthesis". From ammonia and coal tar, aniline dyes were obtained - fuchsine, aniline salt, alizarin, and later - explosives and drugs - aspirin, etc. Structural chemistry gave rise to optimistic statements that chemists can do anything.

However, the further development of chemical science and production based on its achievements showed more precisely the possibilities and limits of structural chemistry. At the level of structural chemistry it was not possible to indicate effective ways producing ethylene, acetylene, benzene and other hydrocarbons from paraffin hydrocarbons. Many organic synthesis reactions based on structural chemistry gave very low outputs required product and large waste in the form side products. And the technological process itself is multi-stage and difficult to manage. As a result, they could not be used on an industrial scale. It was necessary to deepen knowledge about chemical processes.

4. The doctrine of chemical processes.

Chemical processes are a complex phenomenon in both inanimate and living nature. Chemical science faces a fundamental task - to learn manage chemical processes. The fact is that some processes fails to implement, although they are feasible in principle, others hard to stop- combustion reactions, explosions, and some of them difficult to control, since they spontaneously create a lot of by-products.

All chemical reactions have the property reversibility, a redistribution of chemical bonds occurs. Reversibility maintains a balance between forward and reverse reactions. In reality, the equilibrium depends on the process conditions and the purity of the reagents. Shifting the equilibrium in one direction or another requires special ways to control reactions. For example, the reaction for producing ammonia: N 2 + 3H 2 ↔ 2NH 3

This reaction is simple in its composition of elements and structure. However, over the course of a whole century from 1813 to 1913. chemists could not carry it out in a complete form, since the means of controlling it were not known. It was feasible only after the discovery of the corresponding laws by Dutch and French physical chemists I. Van't Hoff and A.D. Le Chatelier. It was found that ammonia synthesis occurs on the surface solid catalyst(specially processed iron) when the equilibrium shifts due to high pressure. Obtaining such pressures is associated with great technological difficulties. With the opening of opportunities organometallic catalyst ammonia synthesis occurs at a normal temperature of 180 o C and normal atmospheric pressure,

Problems of controlling the speed of chemical processes are solved chemical kinetics. It establishes the dependence of chemical reactions on various factors.

Thermodynamic factors, which have a significant impact on the rate of chemical reactions, are temperature And pressure in the reactor. For example, a mixture of hydrogen and oxygen at room temperature and normal pressure can be store for years, and no reaction will occur. But it’s worth passing an electric mixture through spark how will it happen explosion.

The reaction rate depends significantly on temperature. Everyone knows that sugar dissolves more quickly in hot tea than in cold water. Thus, for most chemical reactions, the rate of occurrence with an increase in temperature by 100 o C approximately doubles.

The most active in this regard are compounds of variable composition with weakened connections between their components. It is to them that the action of various catalysts, which significantly accelerate move chemical reactions.

5. Evolutionary chemistry

Chemists have long tried to understand what kind of laboratory underlies the process of the emergence of life from inorganic lifeless matter - a laboratory in which, without human intervention, new chemical compounds are obtained that are more complex than the original substances?

I. Ya. Berzelius(1779-1848) was the first to establish that the basis of living things is biocatalysis, i.e. the presence of various natural substances in a chemical reaction that can control it, slowing down or speeding up its progress. These catalysts in living systems are determined by nature itself. The emergence and evolution of life on Earth would have been impossible without the existence enzymes, essentially serving as living catalysts.

Although enzymes have general properties inherent in all catalysts, however, they are not identical to the latter, since they function within living systems. Therefore attempts to use wildlife experience to accelerate chemical processes in the inorganic world they encounter serious restrictions.

However, modern chemists believe that, based on the study of the chemistry of organisms, it will be possible to create a new control of chemical processes. To solve the problem biocatalysis and using its results on an industrial scale, chemical science has developed a number of methods:

· study and use of living nature techniques,

· application of individual enzymes for modeling biocatalysts,

· mastering the mechanisms of living nature,

· development of research to apply the principles of biocatalysis in chemical processes and chemical technology.

IN evolutionary chemistry significant place is given to the problem self-organization systems In the process of self-organization of prebiological systems, the necessary elements were selected for the emergence of life and its functioning. Of the more than one hundred chemical elements discovered to date, many take part in the life of living organisms. Science believes that only six elements - carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur form the basis of living systems, which is why they get the name organogens. The weight fraction of these elements in a living organism is 97.4%. In addition, the biologically important components of living systems include 12 more elements; sodium, potassium, calcium, magnesium", iron, zinc, silicon, aluminum, chlorine, copper, cobalt, boron.

A special role is assigned to carbon by nature. This element is able to organize connections with elements opposing each other and hold them within itself. Carbon atoms form almost all types chemical bonds. Based on six organogens and about 20 other elements, nature has created about 8 million different chemical compounds that have been discovered to date. 96% of them are organic compounds.

Of this number of organic compounds, only a few hundred are involved in the construction of the bioworld. Of the 100 known amino acids the composition of proteins includes only 20; only four each nucleotide DNA and RNA underlie all complex polymeric nucleic acids responsible for heredity and the regulation of protein synthesis in any living organisms.

How did nature form a complex, highly organized complex from such a limited number of chemical elements and chemical compounds - biosystem?

This process is now presented as follows.

1. In the early stages of the chemical evolution of the world there was no catalysis. Conditions of high temperatures - above 5 thousand degrees Kelvin, electrical discharges and radiation prevent the formation of condensed matter.

2. Manifestations of catalysis begin when easing conditions below 5 thousand degrees, according to Kelvin, and the formation of primary bodies.

3. The role of the catalyst increased(but still only slightly), as physical conditions (mainly temperature) approached modern earthly ones. The appearance of such, even relatively simple systems as: CH 3 OH, CH 2 = CH 2; HC ≡ CH, H 2 CO, HCOOH, HC ≡ N, and especially amino acids, primary sugars, was a kind of non-catalytic preparation for the start of large catalysis.

4. The role of catalysis in the development of chemical systems after reaching the starting state, i.e. famous quantitative minimum organic and inorganic compounds, beginning grow at a fantastic rate. The selection of active compounds occurred in nature from those products that were obtained through a relatively large number of chemical pathways and had a wide catalytic spectrum.

In 1969 it appeared general theory of chemical evolution and biogenesis, put forward earlier in the most general terms by a professor at Moscow University A.P. Rudenko. The essence of this theory is that chemical evolution is the self-development of catalytic systems and, therefore, catalysts are evolving substances. Open A.P. Rudenko fundamental law of chemical evolution states that evolutionary changes in the catalyst occur in the direction where its maximum activity is manifested. The theory of self-development of catalytic systems makes it possible to identify the stages of chemical evolution; give a specific description of the limits in chemical evolution and the transition from chemogenesis (chemical formation) to biogenesis.

Chemical evolution on Earth has created all the prerequisites for the emergence of living things from inanimate nature. And the Earth found itself in such specific conditions that these prerequisites could be realized. Life in all its diversity originated on Earth spontaneously from inanimate matter, it has survived and functioned for billions of years. Life depends entirely on maintaining the appropriate conditions for its functioning. And this largely depends on the person himself. Apparently, one of the manifestations of nature is the appearance of man as self-conscious matter. At a certain stage, it can have a tangible impact on its own habitat, both positive and negative.

In subsequent lectures we will talk in more detail about the essence of life.

Review questions

1. What does chemistry study, and what are the main methods it uses?

2. What relationship exists between atomic weight and the charge of the atomic nucleus?

3. What is a chemical element called?

4. What is called a simple and complex substance?

5. On what factors do the properties of substances depend?

6. Who became the founder of the systematic approach to the development of chemical knowledge? What system did he build?

7. What contribution did physicists make to the development of chemical knowledge?

8. What are catalysts?

9. What elements are called organogens?

10. Why do chemists study the “wildlife” laboratory?

11. How do enzymes differ from chemical catalysts?

12. What are the potential possibilities of evolutionary chemistry?

Literature

Main:

1. Ruzavin G.I. Concepts of modern natural science: A course of lectures. – M.: Gardariki, 2006. Ch. eleven.

2. Concepts of modern natural science / Ed. V.N. Lavrinenko and V.P. Ratnikova. – M.: UNITY-DANA.2003. – Ch. 5.

3. Karpenkov S.Kh. Basic concepts of natural science. – M.: Academic Project, 2002. Ch. 4.

Additional:

1. Azimov A. A brief history of chemistry: Development of ideas and concepts of chemistry from alchemy to the nuclear bomb. – St. Petersburg: Amphora, 2002.

2. Nekrasov B.V. Fundamentals of general chemistry. Ed. 4th. In 2 volumes - St. Petersburg, M., Krasnodar: Lan, 2003.

3. Pimentel D., Kurod D. Possibilities of chemistry today and tomorrow. M., 1992.

4. Fremantle M. Chemistry in action: In 2 hours - M.: Mir, 1998.

5. Emslie J. Elements. - M.: Mir, 1993.

6. Encyclopedia for children. Volume 17. Chemistry / Chapter. Ed. V.A. Volodin. – M.: Avanta+, 2000.

Isotopes are varieties of atoms that have the same nuclear charge but differ in mass.

Quote by: Koltun Mark. World of chemistry. – M.: Det. lit., 1988. P.48.

History of chemistry: alchemy; the period of the unification of chemistry (iatrochemistry, pneumatic chemistry, the phlogiston theory and its opponents, the period of quantitative laws (atomic chemistry)); structuring modern chemical knowledge.

Substance and element. Chemical systems. Energy of chemical processes. Physical bond and chemical reaction. Approaches to the classification of chemical reactions. The rate of a chemical reaction.

Periodic table of elements by D. Mendeleev.

Chemistry of the Earth: geochemistry. Chemistry of life: biochemistry.

Application of chemical knowledge in industry, agriculture, medicine.

Module 3 Wildlife Sciences

Topic 6. Specifics of a biological object and the problem of the origin of life

Specificity of living nature. Concepts of chaos and order. Unity of living and nonliving. Boundaries of life. The phenomenon of life and its interpretation.

Approaches to identifying the specifics of living things: substrate, energy, information. Approaches to defining life: monoattributive, polyattributive.

Specificity and structure of biological knowledge. Tasks of modern biology: solving the problem of the emergence of a biological object, the systemic organization of living things, the evolution of a biological object.

Methodological significance of the principle of historicism in solving the problem of the origin of life. Historical extrapolation.

Evolution of concepts of the origin of life. Biogenesis and abiogenesis. The concept of spontaneous generation of life. Experiments by L. Pasteur. The concept of panspermia and its evolution (S. Arrhenius, V.I. Vernadsky, Hoaldane, Crick). Substrate concept of the origin of life.

Topic 7. Systematic nature of living things and the problem of development of the organic world

The principle of consistency in the study of living things. Polemics of mechanistic and vitalistic trends in biology. Features of living systems: evolutionism, irritability, availability and use of information, self-government, etc.

Criteria for identifying levels of organization of living things. Orderliness of a biological object: spatial, functional, temporal aspects. Levels of organization of living things: the cell and its components, the organism and its properties; species, biogeocenosis.

The origin of the idea of ​​​​the development of living nature in ancient natural philosophy. Naive transformism. Creationism. Systematization of material from botany and zoology. The first taxonomic classifications.

The evolutionary doctrine of Charles Darwin and the approval of the idea of ​​development in biology. Driving forces and factors of evolution. The concepts of “heredity”, “variability”, “natural selection”. Experimental study of individual factors of evolution. Genetics and evolution. Synthetic theory of evolution.

The problem of identifying systemic units of evolution: organism-centric and population approaches. Phylogeny and ontogeny. The problem of managing the evolutionary process.

Topic 8. The problem of the origin and essence of ideal processes

Concept and properties of cybernetic systems. The main stages of the cephalization process. An advanced reflection of reality. Irritability, sensitivity, psyche.

Properties of mental reflection of reality: purposefulness, integrity, subjectivity, objectivity, selectivity, experience, regulation.

Consciousness and its structure. Differences between human consciousness and the psyche of animals.

The origins of chemical knowledge lie in ancient times. They are based on a person’s need to obtain the necessary substances for his life. The origin of the term “chemistry” has not yet been clarified, although there are several versions on this issue. According to one of them, this name comes from the Egyptian word “hemi”, which meant Egypt, as well as “black”. Historians of science also translate this term as “Egyptian art.” Thus, in this version, the word chemistry means the art of producing necessary substances, including the art of transforming ordinary metals into gold and silver or their alloys.

However, another explanation is currently more popular. The word "chemistry" comes from the Greek term "chemos", which can be translated as "plant juice". Therefore, “chemistry” means “the art of obtaining juices,” but the juice in question may also be molten metal. So chemistry can also mean “the art of metallurgy.”

The history of chemistry shows that its development occurred unevenly: periods of accumulation and systematization of data from empirical experiments and observations were replaced by periods of discovery and vigorous discussion of fundamental laws and theories. The sequential alternation of such periods allows us to divide the history of chemical science into several stages.

Main periods of development of chemistry

1. Alchemy period– from antiquity to the 16th century. ad. It is characterized by the search for the philosopher's stone, the elixir of longevity, and alkahest (the universal solvent). In addition, during the alchemical period, almost all cultures practiced the “transformation” of base metals into gold or silver, but all these “transformations” were carried out in very different ways among each people.

2. The period of origin of scientific chemistry, which lasted during the 16th - 18th centuries. At this stage, the theories of Paracelsus, the theories of gases of Boyle, Cavendish and others, the theory of phlogiston by G. Stahl and, finally, the theory of chemical elements by Lavoisier were created. During this period, applied chemistry was improved, associated with the development of metallurgy, glass and porcelain production, the art of distillation of liquids, etc. By the end of the 18th century, chemistry was strengthened as a science independent of other natural sciences.

3. The period of discovery of the basic laws of chemistry covers the first sixty years of the 19th century and is characterized by the emergence and development of Dalton’s atomic theory, Avogadro’s atomic-molecular theory, Berzelius’s establishment of the atomic weights of elements and the formation of the basic concepts of chemistry: atom, molecule, etc.

4. Modern period lasts from the 60s of the 19th century to the present day. This is the most fruitful period in the development of chemistry, since in a little over 100 years the periodic classification of elements, the theory of valence, the theory of aromatic compounds and stereochemistry, Arrhenius's theory of electrolytic dissociation, the electronic theory of matter, etc. were developed.

At the same time, the range of chemical research expanded significantly during this period. Such components of chemistry as inorganic chemistry, organic chemistry, physical chemistry, pharmaceutical chemistry, food chemistry, agricultural chemistry, geochemistry, biochemistry, etc., acquired the status of independent sciences and their own theoretical basis.

Alchemy period

Historically alchemy developed as secret, mystical knowledge aimed at searching for the philosopher's stone, which transforms metals into gold and silver, and the elixir of longevity. During its centuries-old history, alchemy solved many practical problems related to the production of substances and laid the foundation for the creation of scientific chemistry.

Alchemy reached its highest development in three main types:

· Greco-Egyptian;

· Arabic;

· Western European.

The birthplace of alchemy is Egypt. Even in ancient times, methods for obtaining metals and alloys used for the production of coins, weapons, and jewelry were known there. This knowledge was kept secret and was the property of a limited circle of priests. The increasing demand for gold pushed metallurgists to search for ways to transform (transmutate) base metals (iron, lead, copper, etc.) into gold. The alchemical nature of ancient metallurgy connected it with astrology and magic. Each metal had an astrological connection with its corresponding planet. The pursuit of the philosopher's stone allowed us to deepen and expand knowledge about chemical processes. Metallurgy developed, and processes for refining gold and silver were improved. However, during the reign of Emperor Diocletian in Ancient Rome, alchemy began to be persecuted. The possibility of obtaining cheap gold frightened the emperor and, on his orders, all works on alchemy were destroyed. Christianity played a significant role in the prohibition of alchemy, which viewed it as a devilish craft.

After the Arab conquest of Egypt in the 7th century. n. e. alchemy began to develop in Arab countries. The most prominent Arab alchemist was Jabir ibn Khayyam, known in Europe as Geber. He described ammonia, the technology for preparing white lead, and the method of distilling vinegar to produce acetic acid. Jabir's fundamental idea was the theory of the formation of all the then known seven metals from a mixture of mercury and sulfur as two main components. This idea anticipated the division of simple substances into metals and non-metals.

The development of Arab alchemy followed two parallel paths. Some alchemists were engaged in the transmutation of metals into gold, others were looking for the elixir of life, which gave immortality.

The appearance of alchemy in Western European countries became possible thanks to the Crusades. Then the Europeans borrowed scientific and practical knowledge from the Arabs, among which was alchemy. European alchemy came under the auspices of astrology and therefore acquired the character of a secret science. The name of the most outstanding medieval Western European alchemist remains unknown; it is only known that he was a Spaniard and lived in the 14th century. He was the first to describe sulfuric acid, the process of formation of nitric acid, and aqua regia. The undoubted merit of European alchemy was the study and production of mineral acids, salts, alcohol, phosphorus, etc. Alchemists created chemical equipment, developed various chemical operations: heating over direct fire, a water bath, calcination, distillation, sublimation, evaporation, filtering, crystallization, etc. Thus, appropriate conditions were prepared for the development of chemical science.

2. The period of the birth of chemical science covers three centuries: from the 16th to the 19th centuries. The conditions for the formation of chemistry as a science were:

Ø renewal of European culture;

Ø the need for new types of industrial production;

Ø discovery of the New World;

Ø expansion of trade relations.

Having separated from the old alchemy, chemistry acquired greater freedom of research and established itself as a single independent science.

In the 16th century Alchemy was replaced by a new direction that dealt with the preparation of medicines. This direction was called iatrochemistry . The founder of iatrochemistry was a Swiss scientist Theophrastus Bombast von Hohenheim, known in science as Paracelsus.

Iatrochemistry expressed the desire to combine medicine with chemistry, overestimating the role of chemical transformations in the body and attributing to certain chemical compounds the ability to eliminate imbalances in the body. Paracelsus firmly believed that if the human body consists of special substances, then the changes occurring in them should cause diseases that can be cured only by using drugs that restore normal chemical balance. Before Paracelsus, mainly herbal medicines were used as medicines, but he relied only on the effectiveness of medicines made from minerals and therefore sought to create medicines of this type.

In his chemical research, Paracelsus borrowed from the alchemical tradition the doctrine of the three main components of matter - mercury, sulfur and salt, which correspond to the basic properties of matter: volatility, flammability and hardness. These three elements form the basis of the macrocosm (universe), but also apply to the microcosm (man), consisting of spirit, soul and body. Determining the causes of diseases, Paracelsus argued that fever and plague occur from excess sulfur in the body, excess mercury causes paralysis, and excess salt can cause indigestion and dropsy. In the same way, he attributed the causes of many other diseases to an excess or deficiency of these three basic elements.

In preserving human health, Paracelsus attached great importance to chemistry, as he proceeded from the observation that medicine rests on four pillars, namely philosophy, astrology, chemistry and virtue. Chemistry must develop in harmony with medicine, because this union will lead to the progress of both sciences.

Iatrochemistry brought significant benefits to chemistry, as it contributed to its liberation from the influence of alchemy and significantly expanded knowledge about vital compounds, thereby having a beneficial effect on pharmacy. But at the same time, iatrochemistry was also an obstacle to the development of chemistry, because it narrowed the field of its research. For this reason, in the 17th and 18th centuries. a number of researchers abandoned the principles of iatrochemistry and chose a different path for their research, introducing chemistry into life and putting it at the service of man.

It was these researchers who, with their discoveries, contributed to the creation of the first scientific chemical theories.

In the 17th century, in the age of rapid development of mechanics, in connection with the invention of the steam engine, chemistry became interested in the combustion process. The result of these studies was phlogiston theory, the founder of which was a German chemist and doctor Georg Stahl.

Phlogiston theory

Long before the 18th century, Greek and Western alchemists tried to answer these questions: why do some objects burn while others do not? What is the combustion process?

According to the ancient Greeks, everything that can burn contains the element of fire, which can be released under appropriate conditions. Alchemists adhered to approximately the same point of view, but believed that substances capable of combustion contained the element “sulphur”. In 1669 German chemist Johann Becher tried to give a rational explanation for the phenomenon of flammability. He proposed that solids consisted of three types of “earth,” and one of these types, which he called “fat earth,” served as a flammable substance. All these explanations did not answer the question about the essence of the combustion process, but they became the starting point for the creation of a unified theory, known as the phlogiston theory.

Stahl, instead of Becher’s concept of “greasy earth,” introduced the concept of “phlogiston” - from the Greek “phlogistos” - combustible, flammable. The term “phlogiston” became widespread thanks to the work of Stahl himself and because his theory combined numerous information about combustion and calcination.

The phlogiston theory is based on the belief that all combustible substances are rich in a special combustible substance - phlogiston, and the more phlogiston a given body contains, the more capable it is of combustion. What remains after the combustion process is completed does not contain phlogiston and therefore cannot burn. Stahl argues that the melting of metals is similar to the burning of wood. Metals, in his opinion, also contain phlogiston, but when they lose it, they turn into lime, rust or scale. However, if phlogiston is again added to these residues, then metals can again be obtained. When these substances are heated with coal, the metal is “reborn”.

This understanding of the melting process made it possible to provide an acceptable explanation for the process of converting ores into metals - the first theoretical discovery in the field of chemistry.

Stahl's phlogiston theory met with sharp criticism at first, but quickly began to gain popularity in the second half of the 17th century. was accepted by chemists everywhere, as it made it possible to give clear answers to many questions. However, neither Stahl nor his followers were able to resolve one question. The fact is that most flammable substances (wood, paper, fat) largely disappeared when burned. The remaining ash and soot were much lighter than the original material. But chemists of the 18th century. this problem did not seem important, they did not yet realize the importance of accurate measurements, and they neglected the change in weight. The phlogiston theory explained the reasons for changes in the appearance and properties of substances, and changes in weight were unimportant.

The influence of A.L.’s ideas Lavoisier on the development of chemical knowledge

By the end of the 18th century. In chemistry, a large amount of experimental data had been accumulated, which needed to be systematized within the framework of a unified theory. The creator of this theory was the French chemist Antoine-Laurent Lavoisier.

From the very beginning of his activity in the field of chemistry, Lavoisier understood the importance of accurate measurement of substances involved in chemical processes. The use of precise measurements in the study of chemical reactions allowed him to prove the inconsistency of old theories that hindered the development of chemistry.

The question of the nature of the combustion process interested all chemists of the 18th century, and Lavoisier also could not help but become interested in it. His numerous experiments on heating various substances in closed vessels made it possible to establish that, regardless of the nature of chemical processes and their products, the total weight of all substances participating in the reaction remains unchanged.

This allowed him to put forward a new theory of the formation of metals and ores. According to this theory, in the ore the metal is combined with gas. When ore is heated over charcoal, the charcoal absorbs gas from the ore and produces carbon dioxide and metal.

Thus, unlike Stahl, who believed that metal smelting involves the transition of phlogiston from charcoal to ore, Lavoisier imagines this process as the transition of gas from ore to coal. Lavoisier's idea made it possible to explain the reasons for the change in the weight of substances as a result of combustion.

Pondering the results of his experiments, Lavoisier came to the conclusion that if all the substances participating in the chemical reaction and all the products formed were taken into account, then there would never be any changes in weight. In other words, Lavoisier came to the conclusion that mass is never created or destroyed, but only passes from one substance to another. This conclusion, known today as the law of conservation of mass, became the basis for the entire development of chemistry in the 19th century.

However, Lavoisier himself was dissatisfied with the results obtained, since he did not understand why scale was formed when air was combined with metal, and gases were formed when air was combined with wood, and why not all of the air, but only about a fifth of it, was involved in these interactions?

Again, as a result of numerous experiments and experiments, Lavoisier came to the conclusion that air is not a simple substance, but a mixture of two gases. One fifth of the air, according to Lavoisier, is “dephlogisticated air,” which combines with burning and rusting objects, passes from ores to charcoal and is necessary for life. Lavoisier called this gas oxygen, that is, the gas that generates acids, since he mistakenly believed that oxygen is a component of all acids.

The second gas, comprising four-fifths of air (“phlogisticated air”), was recognized as a completely independent substance. This gas did not support combustion, and Lavoisier called it nitrogen - lifeless.

An important role in Lavoisier’s research was played by the results of the experiments of the English physicist Cavendish, who proved that gases formed during combustion condense into a liquid, which, as tests showed, is just water.

The importance of this discovery was enormous, as it turned out that water is not a simple substance, but a product of the combination of two gases.

Lavoisier called the gas released during combustion hydrogen (“forming water”) and noted that hydrogen burns by combining with oxygen, and therefore water is a compound of hydrogen and oxygen.

Lavoisier's new theories entailed a complete rationalization of chemistry. All mysterious elements were finally dealt with. From that time on, chemists became interested only in those substances that could be weighed or measured in some other way.