Vyatka State Humanitarian University

Department of Chemistry

Oxygen cycle in nature

The work was completed by a student

Kazakovtseva Natalya Yurievna

1.The concept of circulation

Oxygen cycle in nature

1 General information about the oxygen element

2 Oxygen cycle

List of used literature

1. The concept of circulation

There is a constant exchange of chemical elements between the lithosphere, hydrosphere, atmosphere and living organisms of the Earth. This process is cyclical: having moved from one sphere to another, the elements return to their original state. The cycle of elements has taken place throughout the history of the Earth, which spans 4.5 billion years.

The cycle of substances is a repeatedly repeated process of joint, interconnected transformation and movement of substances in nature, which has a more or less cyclical nature. The general circulation of substances is characteristic of all geospheres and consists of individual processes of the circulation of chemical elements, water, gases and other substances. The circulation processes are not completely reversible due to the dispersion of substances, changes in its composition, local concentration and deconcentration.

To substantiate and explain the very concept of a cycle, it is useful to refer to the four most important principles of geochemistry, which are of paramount applied importance and confirmed by indisputable experimental data:

A) widespread distribution of chemical elements in all geospheres;

b) continuous migration (movement) of elements in time and space;

V) the diversity of types and forms of existence of elements in nature;

Most of all, in my opinion, it is worth focusing your attention on the process of moving chemical elements.

The migration of chemical elements is reflected in the gigantic tectonic-magamtic processes that transform the earth's crust, and in the finest chemical reactions occurring in living matter, in the continuous progressive development of the surrounding world, characterizing movement as a form of existence of matter. The migration of chemical elements is determined by numerous external factors, in particular, the energy of solar radiation, the internal energy of the Earth, the action of gravity and internal factors depending on the properties of the elements themselves.

Cycles can occur in a limited space and over short periods of time, or they can cover the entire outer part of the planet and over huge periods. In this case, small cycles are included in larger ones, which together form colossal biogeochemical cycles. They are closely related to the environment.

Giant masses of chemicals are transported by the waters of the World Ocean. This primarily applies to dissolved gases - carbon dioxide, oxygen, nitrogen. Cold water at high latitudes dissolves atmospheric gases. Coming with ocean currents into the tropical zone, it releases them, since the solubility of gases decreases when heated. The absorption and release of gases also occurs during the change of warm and cold seasons of the year.

The emergence of life on the planet had a huge impact on the natural cycles of some elements. This, first of all, refers to the circulation of the main elements of organic matter - carbon, hydrogen and oxygen, as well as such vital elements as nitrogen, sulfur and phosphorus. Living organisms also influence the cycle of many metal elements. Despite the fact that the total mass of living organisms on Earth is millions of times less than the mass of the earth's crust, plants and animals play a vital role in the movement of chemical elements. There is a law of global closure of the biogeochemical cycle in the biosphere, operating at all stages of its development, as well as the rule of increasing closure of the biogeochemical cycle during succession (succession (from the Latin succesio - continuity) - a sequential change of ecosystems that successively arise on a certain area of ​​the earth's surface. Usually succession occurs under the influence of the processes of internal development of communities, their interaction with the environment. The duration of succession ranges from tens to millions of years). In the process of biosphere evolution, the role of the biological component in closing the biogeochemical cycle increases.

Human activities also influence the cycle of elements. It has become especially noticeable in the last century. When considering the chemical aspects of global changes in chemical cycles, one must take into account not only changes in natural cycles due to the addition or removal of chemicals present in them as a result of normal cyclic and/or human-induced impacts, but also the release of chemicals into the environment that were not previously existing in nature.

The cycles of elements and substances are carried out due to self-regulating processes in which all components of ecosystems participate. These processes are waste-free. There is nothing useless or harmful in nature; even volcanic eruptions have benefits, since the necessary elements, for example, nitrogen and sulfur, are released into the air with volcanic gases.

There are two main cycles: large (geological) and small (biotic).

The great cycle, which continues for millions of years, consists in the fact that rocks are destroyed, and weathering products (including water-soluble nutrients) are carried by water flows into the World Ocean, where they form marine strata and only partially return to land with precipitation . Geotectonic changes, processes of subsidence of continents and rise of the seabed, movement of seas and oceans over a long period of time lead to the fact that these strata return to land and the process begins again.

The small cycle, being part of the large one, occurs at the ecosystem level and consists in the fact that nutrients, water and carbon accumulate in the substance of plants, are spent on building the body and on the life processes of both the plants themselves and other organisms (usually animals) who eat them. The decay products of organic matter under the influence of destructors and microorganisms (bacteria, fungi, worms) again decompose into mineral components that are accessible to plants and are drawn into the flow of matter by them.

Thus, the circulation of chemicals from the inorganic environment through plant and animal organisms back into the inorganic environment using solar energy and the energy of chemical reactions is called the biogeochemical cycle. Almost all chemical elements are involved in such cycles, and primarily those that are involved in the construction of a living cell.

2. Oxygen cycle in nature

1 General information about the oxygen element

History of discovery.It is officially believed that oxygen was discovered by the English chemist Joseph Priestley on August 1, 1774 by decomposing mercuric oxide in a hermetically sealed vessel (Priestley directed sunlight at this compound using a powerful lens):

HgO(t)→ 2Hg + O 2

However, Priestley initially did not realize that he had discovered a new simple substance. He believed that he had isolated one of the constituents of air (and called this gas “dephlogisticated air”). Priestley reported his discovery to the outstanding French chemist Antoine Lavoisier.

A few years earlier (possibly in 1770), oxygen was obtained by the Swedish chemist Karl Scheele. He calcined saltpeter with sulfuric acid and then decomposed the resulting nitric oxide. Scheele called this gas “fire air” and described his discovery in a book published in 1777 (precisely because the book was published later than Priestley announced his discovery, the latter is considered the discoverer of oxygen). Scheele also reported his experience to Lavoisier.

An important stage that contributed to the discovery of oxygen was the work of the French chemist Peter Bayen, who published works on the oxidation of mercury and the subsequent decomposition of its oxide.

Finally, Antoine Lavoisier finally figured out the nature of the resulting gas, using information from Priestley and Scheele. His work was of enormous importance, because thanks to it, the phlogiston theory (phlogiston) that was dominant at that time and hampered the development of chemistry was overthrown ́ n (from the Greek phlogistos - flammable, flammable) - a hypothetical “fiery substance” that supposedly fills all flammable substances and is released from them during combustion). Lavoisier conducted experiments on the combustion of various substances and disproved the theory of phlogiston, publishing results on the weight of the elements burned. The weight of the ash exceeded the original weight of the element, which gave Lavoisier the right to claim that during combustion a chemical reaction (oxidation) of the substance occurs, and therefore the mass of the original substance increases, which refutes the theories of phlogiston.

Thus, the credit for the discovery of oxygen is actually shared between Priestley, Scheele and Lavoisier.

Being in nature.Oxygen is the most common element on Earth; its share (in various compounds, mainly silicates) accounts for about 47.4% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 88.8% (by mass), in the atmosphere the content of free oxygen is 20.95% (by volume). The element oxygen is part of more than 1,500 compounds in the earth's crust.

Physical properties.Under normal conditions, the density of oxygen gas is 1.42897 g/l. The boiling point of liquid oxygen (the liquid is blue) is -182.9 °C. In the solid state, oxygen exists in at least three crystalline modifications. At 20°C the solubility of gas O 2: 3.1 ml per 100 ml of water, 22 ml per 100 ml of ethanol, 23.1 ml per 100 ml of acetone. There are organic fluorine-containing liquids (for example, perfluorobutyltetrahydrofuran), in which the solubility of oxygen is much higher.

Chemical propertieselement are determined by its electronic configuration: 2s 22p 4. High strength of chemical bonds between atoms in the O molecule 2leads to the fact that at room temperature oxygen gas is chemically quite inactive. In nature, it slowly undergoes transformation during decay processes. In addition, oxygen at room temperature is able to react with hemoglobin in the blood (more precisely, with iron (II) heme (heme is a derivative of porphyrin containing a divalent iron atom in the center of the molecule), which ensures the transfer of oxygen from the respiratory organs to other organs.

Oxygen reacts with many substances without heating, for example, with alkali and alkaline earth substances, causing the formation of rust on the surface of steel products. Without heating, oxygen reacts with white phosphorus, with some aldehydes and other organic substances.

When heated, even slightly, the chemical activity of oxygen increases sharply. When ignited, it reacts explosively with hydrogen, methane, other flammable gases, and a large number of simple and complex substances. It is known that when heated in an oxygen atmosphere or in air, many simple and complex substances burn, and various oxides, peroxides and superoxides are formed, such as SO 2, Fe 2O 3, N 2ABOUT 2, VaO 2, KO 2.

If a mixture of oxygen and hydrogen is stored in a glass vessel at room temperature, then the exothermic reaction to form water

N 2+ O 2= 2H 2O + 571 kJ

proceeds extremely slowly; According to calculations, the first drops of water should appear in the vessel in about a million years. But when platinum or palladium (playing the role of a catalyst) is introduced into a vessel with a mixture of these gases, as well as when ignited, the reaction proceeds with an explosion.

With nitrogen N 2oxygen reacts either at high temperature (about 1500-2000 °C), or by passing an electrical discharge through a mixture of nitrogen and oxygen. Under these conditions, nitric oxide (II) is reversibly formed:

2+O 2= 2NO.

The resulting NO then reacts with oxygen to form brown gas (nitrogen dioxide):

NO + O 2= 2NO 2

Of non-metals, oxygen does not directly interact with halogens under any circumstances, and of metals - with silver, gold, platinum and platinum group metals.

With the most active nonmetal fluorine, oxygen forms compounds in positive oxidation states. So, in the compound O 2F 2the oxidation state of oxygen is +1, and in the compound O 2F - +2. These compounds do not belong to oxides, but to fluorides. Oxygen fluorides can only be synthesized indirectly, for example, by acting with fluorine F 2to dilute aqueous solutions of KOH.

Application.The uses of oxygen are very diverse. The main quantities of oxygen obtained from the air are used in metallurgy. Oxygen (rather than air) blast in blast furnaces can significantly increase the speed of the blast furnace process, save coke and produce cast iron of better quality. Oxygen blast is used in oxygen converters when converting cast iron into steel. Pure oxygen or air enriched with oxygen is used in the production of many other metals (copper, nickel, lead, etc.). Oxygen is used in cutting and welding metals. In this case, compressed gaseous oxygen is used, stored under a pressure of 15 MPa in special steel cylinders. Oxygen cylinders are painted blue to distinguish them from cylinders with other gases.

Liquid oxygen is a powerful oxidizing agent and is used as a component of rocket fuel. A mixture of liquid oxygen and liquid ozone is one of the most powerful oxidizers of rocket fuel. Soaked in liquid oxygen, easily oxidizing materials such as sawdust, cotton wool, coal powder, etc. (these mixtures are called oxyliquits) are used as explosives, used, for example, in laying roads in the mountains.

oxygen cycle chemical element

2.2 Oxygen cycle

Oxygen is the most abundant element on Earth. Sea water contains 88.8% oxygen, atmospheric air contains 23.15% by weight or 20.95% by volume, and the earth's crust contains 47.4% by weight.

Along with this, a powerful source of oxygen is, apparently, the photochemical decomposition of water vapor in the upper layers of the atmosphere under the influence of ultraviolet rays of the sun.

Fig.1. Conditional diagram of photosynthesis.

Oxygen is the main biogenic element that is part of the molecules of all the most important substances that provide the structure and function of cells - proteins, nucleic acids, carbohydrates, lipids, as well as many low-molecular compounds. Every plant or animal contains much more oxygen than any other element (on average about 70%). Human muscle tissue contains 16% oxygen, bone tissue - 28.5%; In total, the body of an average person (body weight 70 kg) contains 43 kg of oxygen. Oxygen enters the body of animals and humans mainly through the respiratory organs (free oxygen) and with water (bound oxygen). The body's need for oxygen is determined by the level (intensity) of metabolism, which depends on the mass and surface of the body, age, gender, nutritional pattern, external conditions, etc. In ecology, the ratio of total respiration (that is, total oxidative processes) of a community is determined as an important energy characteristic organisms to its total biomass.

In natural life, oxygen is of exceptional importance. Oxygen and its compounds are indispensable for maintaining life. They play a vital role in metabolic processes and respiration. Most organisms obtain the energy necessary to perform their vital functions through the oxidation of certain substances with the help of oxygen. The loss of oxygen in the atmosphere as a result of the processes of respiration, decay and combustion is compensated by oxygen released during photosynthesis.

A small amount of atmospheric oxygen participates in the cycle of formation and destruction of ozone under strong ultraviolet radiation:

O 2→ O 2*

O 2*+O 2→ O 3+O

O+O 2→ O 3

O 3 → 3O 2

Most of the oxygen produced during geological epochs did not remain in the atmosphere, but was fixed by the lithosphere in the form of carbonates, sulfates, iron oxides, etc.

The geochemical oxygen cycle connects the gas and liquid shells with the earth's crust. Its main points: the release of free oxygen during photosynthesis, the oxidation of chemical elements, the entry of extremely oxidized compounds into the deep zones of the earth's crust and their partial reduction, including due to carbon compounds, the removal of carbon monoxide and water to the surface of the earth's crust and their involvement in the reaction photosynthesis. A diagram of the oxygen cycle in unbound form is presented below.

Fig.2. Diagram of the oxygen cycle in nature.

In addition to the oxygen cycle described above in an unbound form, this element also completes the most important cycle, entering the composition of water (Fig. 3). During the cycle, water evaporates from the surface of the ocean, water vapor moves along with air currents, condenses, and water returns in the form of precipitation to the surface of land and sea. There is a large water cycle, in which water that falls as precipitation on land returns to the seas through surface and underground runoff; and the small water cycle, which deposits precipitation on the ocean surface.

From the given examples of cycles and migration of an element, it is clear that the global system of cyclic migration of chemical elements has a high ability for self-regulation, while the biosphere plays a huge role in the cycle of chemical elements.

At the same time, human economic activity causes deformation of natural mass exchange cycles and, consequently, changes in the composition of the environment. These changes occur much faster than the processes of genetic adaptation of organisms and speciation. Often, economic actions are so ill-conceived or imperfect that they create an acute environmental hazard. The study of mass transfer processes that connect all the Earth's shells into a single whole should help in creating a system for monitoring the ecological and geochemical state of the environment and developing a scientifically based forecast of the environmental consequences of economic actions and new technologies.

References

1. Dobrovolsky V.V. Fundamentals of biogeochemistry. Textbook manual for geogr., biol., geol., agricultural. specialist. universities M.: Higher. school, 1998

2. Kamensky A.A., Sokolova N.A., Valovaya M.A. Basics of biology. Full course of comprehensive secondary school / A.A. Kamensky, N.A. Sokolova, M.A. Gross. - M.: Publishing house "Exam", 2004 - 448 p.

Internet resource http://ru.wikipedia.org/

1. The concept of circulation

2. Oxygen cycle

2.1. General information about the oxygen element

2.2. Oxygen cycle

List of used literature

1. The concept of circulation.

There is a constant exchange of chemical elements between the lithosphere, hydrosphere, atmosphere and living organisms of the Earth. This process is cyclical: having moved from one sphere to another, the elements return to their original state. The cycle of elements has taken place throughout the history of the Earth, which spans 4.5 billion years.

The cycle of substances is a repeatedly repeated process of joint, interconnected transformation and movement of substances in nature, which has a more or less cyclical nature. The general circulation of substances is characteristic of all geospheres and consists of individual processes of the circulation of chemical elements, water, gases and other substances. The circulation processes are not completely reversible due to the dispersion of substances, changes in its composition, local concentration and deconcentration.

To substantiate and explain the very concept of a cycle, it is useful to refer to the four most important principles of geochemistry, which are of paramount applied importance and confirmed by indisputable experimental data:

a) widespread distribution of chemical elements in all geospheres;

b) continuous migration (movement) of elements in time and space;

c) the variety of types and forms of existence of elements in nature;

d) the predominance of the dispersed state of elements over the concentrated state, especially for ore-forming elements.

Most of all, in my opinion, it is worth focusing your attention on the process of moving chemical elements.

The migration of chemical elements is reflected in the gigantic tectonic-magamtic processes that transform the earth's crust, and in the finest chemical reactions occurring in living matter, in the continuous progressive development of the surrounding world, characterizing movement as a form of existence of matter. The migration of chemical elements is determined by numerous external factors, in particular, the energy of solar radiation, the internal energy of the Earth, the action of gravity and internal factors depending on the properties of the elements themselves.

Cycles can occur in a limited space and over short periods of time, or they can cover the entire outer part of the planet and over huge periods. In this case, small cycles are included in larger ones, which together form colossal biogeochemical cycles. They are closely related to the environment.

Giant masses of chemicals are transported by the waters of the World Ocean. This primarily applies to dissolved gases - carbon dioxide, oxygen, nitrogen. Cold water at high latitudes dissolves atmospheric gases. Coming with ocean currents into the tropical zone, it releases them, since the solubility of gases decreases when heated. The absorption and release of gases also occurs during the change of warm and cold seasons of the year.

The emergence of life on the planet had a huge impact on the natural cycles of some elements. This, first of all, refers to the circulation of the main elements of organic matter - carbon, hydrogen and oxygen, as well as such vital elements as nitrogen, sulfur and phosphorus. Living organisms also influence the cycle of many metal elements. Despite the fact that the total mass of living organisms on Earth is millions of times less than the mass of the earth's crust, plants and animals play a vital role in the movement of chemical elements. There is a law of global closure of the biogeochemical cycle in the biosphere, which operates at all stages of its development, as well as the rule of increasing closure of the biogeochemical cycle during succession. In the process of biosphere evolution, the role of the biological component in closing the biogeochemical cycle increases.

Human activities also influence the cycle of elements. It has become especially noticeable in the last century. When considering the chemical aspects of global changes in chemical cycles, one must take into account not only changes in natural cycles due to the addition or removal of chemicals present in them as a result of normal cyclic and/or human-induced impacts, but also the release of chemicals into the environment that were not previously existing in nature.

The cycles of elements and substances are carried out due to self-regulating processes in which all components of ecosystems participate. These processes are waste-free. There is nothing useless or harmful in nature; even volcanic eruptions have benefits, since the necessary elements, for example, nitrogen and sulfur, are released into the air with volcanic gases.

There are two main cycles: large (geological) and small (biotic).

The great cycle, which continues for millions of years, consists in the fact that rocks are destroyed, and weathering products (including water-soluble nutrients) are carried by water flows into the World Ocean, where they form marine strata and only partially return to land with precipitation . Geotectonic changes, processes of subsidence of continents and rise of the seabed, movement of seas and oceans over a long period of time lead to the fact that these strata return to land and the process begins again.

The small cycle, being part of the large one, occurs at the ecosystem level and consists in the fact that nutrients, water and carbon accumulate in the substance of plants, are spent on building the body and on the life processes of both the plants themselves and other organisms (usually animals) who eat them. The decay products of organic matter under the influence of destructors and microorganisms (bacteria, fungi, worms) again decompose into mineral components that are accessible to plants and are drawn into the flow of matter by them.

Thus, the circulation of chemicals from the inorganic environment through plant and animal organisms back into the inorganic environment using solar energy and the energy of chemical reactions is called the biogeochemical cycle. Almost all chemical elements are involved in such cycles, and primarily those that are involved in the construction of a living cell.

2. The oxygen cycle in nature.

2.1. General information about the oxygen element.

History of discovery. It is officially believed that oxygen was discovered by the English chemist Joseph Priestley on August 1, 1774 by decomposing mercuric oxide in a hermetically sealed vessel (Priestley directed sunlight at this compound using a powerful lens):

2HgO(t)→ 2Hg + O2

However, Priestley initially did not realize that he had discovered a new simple substance. He believed that he had isolated one of the constituents of air (and called this gas “dephlogisticated air”). Priestley reported his discovery to the outstanding French chemist Antoine Lavoisier.

A few years earlier (possibly in 1770), oxygen was obtained by the Swedish chemist Karl Scheele. He calcined saltpeter with sulfuric acid and then decomposed the resulting nitric oxide. Scheele called this gas “fire air” and described his discovery in a book published in 1777 (precisely because the book was published later than Priestley announced his discovery, the latter is considered the discoverer of oxygen). Scheele also reported his experience to Lavoisier.

Oxygen (O2) was discovered. As a result of an experiment carried out in a closed vessel with mercury oxide, under the influence of sunlight directed by a lens, its decomposition occurred: 2HgO → O2 + 2Hg. This gaseous substance is characterized by a density under normal conditions of 0.00142897 g/cm³, a molar volume of 14.0 cm³/mol, a melting point of minus 218.2 °C and a boiling point of minus 182.81 °C. The molar mass is 15.9994 g/mol. The main characteristic of oxygen is its ability to oxidize various substances. As an active nonmetal, O2 reacts with all metals to form basic and amphoteric oxides, as well as with all nonmetals (except halogens), resulting in acidic or non-salt-forming oxides.

Oxygen is part of more than one and a half thousand substances, as it is the most common chemical element on Earth. It is part of various chemical compounds (there are more than one and a half thousand of them). In the solid earth's crust, the O2 content is 47.4%. In marine and bound states it accounts for 88.8% of the mass. In the atmosphere, oxygen is in a free state, its volume fraction is approximately 21%, and its mass fraction is 23.1%. It is an essential component of organic substances that are present in every living cell. It occupies 25% by volume and 65% by mass. The oxygen cycle in nature is determined by its chemical activity.

A cycle is a series of changes in a substance, as a result of which it returns to its starting point, and the entire path is repeated. The oxygen cycle is a biogeochemical movement. Through it, O2 passes through the biotic sum of all ecosystems (biosphere or zone of life on Earth) and abiotic (lithosphere, atmosphere and hydrosphere) environments. The oxygen cycle describes its movement in the hydrosphere (the mass of water located underground and above its surface), the atmosphere (air), the biosphere (the global sum of all ecosystems) and the lithosphere (the earth's crust). Disruptions to this cycle in the hydrosphere can lead to the development of hypoxic (low O2) zones in large lakes and the ocean. The main driving factor is photosynthesis.

Ecological systems (ecosystems) have many biogeochemical cycles operating in their composition. For example, the water cycle, oxygen cycle, nitrogen cycle, carbon cycle, etc. All chemical elements undergo a path that is part of biogeochemical cycles. They are an integral part of living organisms, but also move through the abiotic environments of ecosystems. These are water (hydrosphere), earth's crust (lithosphere) and air (atmosphere). Living organisms fill the shell of the Earth, called the biosphere. All the nutrients such as carbon, nitrogen, oxygen, phosphorus and sulfur are used by them and are part of a closed system, so they are recycled rather than lost and constantly replenished as in an open system.

The largest reservoir of O2 (99.5%) is the crust and where it is found in silicate and oxide minerals. The oxygen cycle ensured that only a small part entered the biosphere (0.01%) and the atmosphere (0.36%) in the form of free O2. The main source of atmospheric free O2 is photosynthesis. Its products are organic substances and free oxygen formed from carbon dioxide and water: 6CO2 + 6H2O + energy → C6H12O6 + 6O2.

Land plants, as well as phytoplankton of the oceans, are responsible for the oxygen cycle in the biosphere. The tiny marine cyanobacteria (blue-green algae) Prochlorococcus, measuring 0.6 microns in size, was discovered in 1986. They account for more than half of the products of photosynthesis in the open ocean. An additional source of free atmospheric oxygen is the phenomenon of photolysis (a chemical reaction occurring under the influence of photons). As a result, atmospheric water dissociates into its constituent atoms, hydrogen (H) and nitrogen (N) are removed to space, and O2 remains in the atmosphere: 2H2O + energy → 4H + O2 and 2N2O + energy → 4N + O2. Free atmospheric oxygen is consumed by living organisms in the processes of respiration and decay. The lithosphere uses free O2 through chemical weathering and surface reactions. For example, it is spent on the formation (of rust): 4FeO + O2 → 2Fe2O3 or oxides of other metals and non-metals.

The oxygen cycle also includes a cycle between the biosphere and lithosphere. Marine organisms in the biosphere serve as sources of (CaCO3), which is rich in O2. When an organism dies, its shell is carried to the shallow seabed, where it remains for a long time and forms limestone (sedimentary rock of the earth's crust). Weathering processes initiated by the biosphere can also remove free oxygen from the lithosphere. Plants and animals extract nutrients from sediment and release oxygen.

The Earth contains 49.4% oxygen, which occurs either free in the air or bound (water, compounds and minerals).

Characteristics of oxygen

On our planet, oxygen gas is more common than any other chemical element. And this is not surprising, because it is part of:

• rocks,
• water,
• atmosphere,
• living organisms,
• proteins, carbohydrates and fats.

Oxygen is an active gas and supports combustion.

Physical properties

Oxygen is found in the atmosphere in a colorless gaseous form. It is odorless and slightly soluble in water and other solvents. Oxygen has strong molecular bonds, which makes it chemically inactive.

If oxygen is heated, it begins to oxidize and react with most non-metals and metals. For example, iron, this gas slowly oxidizes and causes it to rust.

With a decrease in temperature (-182.9 ° C) and normal pressure, gaseous oxygen transforms into another state (liquid) and acquires a pale blue color. If the temperature is further reduced (to -218.7°C), the gas will solidify and change to the state of blue crystals.

In liquid and solid states, oxygen turns blue and has magnetic properties.

Charcoal is an active oxygen absorber.

Chemical properties

Almost all reactions of oxygen with other substances produce and release energy, the strength of which can depend on temperature. For example, at normal temperatures this gas reacts slowly with hydrogen, and at temperatures above 550°C an explosive reaction occurs.

Oxygen is an active gas that reacts with most metals except platinum and gold. The strength and dynamics of the interaction during which oxides are formed depends on the presence of impurities in the metal, the state of its surface and grinding. Some metals, when combined with oxygen, in addition to basic oxides, form amphoteric and acidic oxides. Oxides of gold and platinum metals arise during their decomposition.

Oxygen, in addition to metals, also actively interacts with almost all chemical elements (except halogens).

In its molecular state, oxygen is more active and this feature is used in the bleaching of various materials.

The role and importance of oxygen in nature

Green plants produce the most oxygen on Earth, with the bulk produced by aquatic plants. If more oxygen is produced in the water, the excess will go into the air. And if it is less, then on the contrary, the missing amount will be supplemented from the air.

Sea and fresh water contains 88.8% oxygen (by mass), and in the atmosphere it is 20.95% by volume. In the earth's crust, more than 1,500 compounds contain oxygen.

Of all the gases that make up the atmosphere, oxygen is the most important for nature and humans. It is present in every living cell and is necessary for all living organisms to breathe. The lack of oxygen in the air immediately affects life. Without oxygen it is impossible to breathe, and therefore to live. A person breathing for 1 minute. on average it consumes 0.5 dm3. If there is less of it in the air to 1/3 of it, then he will lose consciousness, to 1/4 of it, he will die.

Yeast and some bacteria can live without oxygen, but warm-blooded animals die within minutes if there is a lack of oxygen.

Oxygen cycle in nature

The oxygen cycle in nature is the exchange of oxygen between the atmosphere and oceans, between animals and plants during respiration, as well as during chemical combustion.

On our planet, an important source of oxygen is plants, which undergo a unique process of photosynthesis. During this, oxygen is released.

In the upper part of the atmosphere, oxygen is also formed due to the division of water under the influence of the Sun.

How does the oxygen cycle occur in nature?

During the respiration of animals, people and plants, as well as the combustion of any fuel, oxygen is consumed and carbon dioxide is formed. Then the carbon dioxide feeds the plants, which again produce oxygen through the process of photosynthesis.

Thus, its content in the atmospheric air is maintained and does not end.

Applications of oxygen

In medicine, during operations and life-threatening diseases, patients are given pure oxygen to breathe in order to alleviate their condition and speed up recovery.

Without oxygen cylinders, climbers cannot climb mountains, and scuba divers cannot dive to the depths of seas and oceans.

Oxygen is widely used in various types of industry and production:

• for cutting and welding various metals
• for obtaining very high temperatures in factories
• to obtain a variety of chemical compounds. to accelerate the melting of metals.

Oxygen is also widely used in the space industry and aviation.

Oxygen is the most common element in the earth's crust. In a free state, it is found in the atmospheric air; in a bound form, it is part of water, minerals, rocks and all substances from which the organisms of plants and animals are built. The mass fraction of oxygen in the earth's crust is about 47%.

Oxygen is a colorless, odorless gas. It is slightly heavier than air. Oxygen plays an extremely important role in nature. With the participation of oxygen, one of the most important life processes occurs - respiration.. Another process in which oxygen is involved is also important - smoldering and rotting of dead animals and plants; in this case, complex organic substances are converted into simpler ones (ultimately into CO 2, water and nitrogen), and the latter re-enter the general cycle of substances in nature.

Oxygen is the most active gas. Within the biosphere, there is a rapid exchange of environmental oxygen with living organisms or their remains after death.

In the composition of the earth's atmosphere, oxygen ranks second after nitrogen. The dominant form of oxygen in the atmosphere is the O 2 molecule. The oxygen cycle in the biosphere is very complex, since it enters into many chemical compounds of the mineral and organic worlds.

The oxygen cycle mainly occurs between the atmosphere and living organisms. Basically, free oxygen (O2) enters the atmosphere as a result of photosynthesis of green plants, and is consumed in the process of respiration by animals, plants and microorganisms, and during the mineralization of organic residues (rotting of various substances). A small amount of oxygen is formed from water and ozone under the influence of ultraviolet radiation.

There came a time in the history of the Earth's biosphere when the amount of free oxygen reached a certain level and turned out to be balanced in such a way that the amount of oxygen released became equal to the amount of oxygen absorbed.

A large amount of oxygen is consumed by oxidative processes in the earth’s crust, during volcanic eruptions, etc.

The main share of oxygen is produced by land plants - almost 3/4, the rest - by photosynthetic organisms of the World Ocean. The speed of the cycle is about 2 thousand years.

The volumes of flows of oxygen and oxygen-containing compounds established in the biosphere under modern conditions are disrupted by technogenic migrations. Industrial, household and agricultural waste discharged into natural waters (rivers, lakes, seas, oceans) bind oxygen dissolved in water, which also disrupts the volume of oxygen flows in the biosphere. Soil pollution and deforestation reduce the exchange of oxygen and carbon dioxide between the atmosphere and land. However, the reserves of oxygen on the planet are inexhaustible. It is part of the crystalline lattices of minerals and is released from them with the help of living matter. Therefore, in order to maintain steady-state volumes of oxygen flows in the biosphere, it is necessary to preserve living matter as the main geochemical force.

It has been established that 23% of the oxygen produced during photosynthesis is annually consumed for industrial and domestic needs, and this figure is constantly increasing.

Oxygen atmosphere accumulated as a result of the activity of green plants. It took about 2.5–3 billion years to create the current composition of the atmosphere, containing 21% oxygen.

All free oxygen in the atmosphere is estimated at 1.6 × 10 9 tons. This amount is consumed for respiration by living organisms over 2 thousand years, which is the time of the complete oxygen cycle in the biosphere.

Oxygen cycle in the biosphere (Cloud, Jibor, 1972)

At the upper boundary of the troposphere, under the influence of cosmic radiation, ozone is formed from oxygen. Consequently, the ozone screen, which protects life from deadly radiation, is also the result of the activity of living matter, that is, life itself protects itself from death. This fact confirms the Gen hypothesis, according to which global processes that determine the limits of life are regulated only by the biological processes of the biosphere itself.