Crafts

Definition of the word diffusion in biology. Diffusion in the biology of wound healing. Diffusion in the plant kingdom

V school curriculum in the physics course (approximately in the seventh grade), schoolchildren will learn that diffusion is a process that is the mutual penetration of particles of one substance between particles of another substance, as a result of which the concentrations are equalized in the entire occupied volume. This definition is quite difficult to understand. To understand what simple diffusion is, the law of diffusion, its equation, it is necessary to study in detail the materials on these issues. However, if a general idea is enough for a person, then the data below will help to obtain basic knowledge.

Physical phenomenon - what is it

Due to the fact that many people are confused or do not know at all what a physical phenomenon is and how it differs from a chemical one, as well as what type of phenomena diffusion belongs to, it is necessary to understand what a physical phenomenon is. So, as everyone knows, physics is an independent science belonging to the field of natural science, which studies general natural laws about the structure and motion of matter, and also studies matter itself. Accordingly, a physical phenomenon is such a phenomenon as a result of which new substances are not formed, but only a change in the structure of the substance occurs. The difference between a physical phenomenon and a chemical one lies precisely in the fact that new substances are not obtained as a result. Thus, diffusion is a physical phenomenon.

Definition of the term diffusion

As you know, there can be many formulations of this or that concept, but the general meaning should not change. And the phenomenon of diffusion is no exception. The generalized definition is as follows: diffusion is a physical phenomenon that is the mutual penetration of particles (molecules, atoms) of two or more substances until they are evenly distributed over the entire volume occupied by these substances. As a result of diffusion, no new substances are formed, therefore it is precisely a physical phenomenon. Simple diffusion is called diffusion, as a result of which the movement of particles from the region of the highest concentration to the region of lower concentration occurs, which is due to the thermal (chaotic, Brownian) motion of the particles. In other words, diffusion is the process of mixing particles of different substances, and the particles are distributed evenly throughout the volume. This is a very simplified definition, but the most understandable.

Diffusion types

Diffusion can be detected both when observing gaseous and liquid substances, as well as solid ones. Therefore, it includes several types:

Quantum diffusion is the process of diffusion of particles or point defects (local violations of the crystal lattice of a substance), which takes place in solids. Local disturbances are disturbances at a certain point in the crystal lattice.

Colloidal - diffusion that occurs in the entire volume of the colloidal system. A colloidal system is a medium in which particles, bubbles, drops of another medium differing in their state of aggregation and composition from the first are distributed. Such systems, as well as the processes occurring in them, are studied in detail in the course of colloidal chemistry.
Convective - transfer of microparticles of one substance by medium macroparticles. A special branch of physics, called hydrodynamics, deals with the study of the motion of continuous media. From there, you can glean knowledge about the states of the flow.
Turbulent diffusion is the process of transfer of one substance to another, due to the turbulent movement of the second substance (typical for gases and liquids).

The statement is confirmed that diffusion can occur both in gases and liquids, and in solids.

What is Fick's Law?

A German scientist, physicist Fick, derived a law showing the dependence of the particle flux density through a unit area on the change in the concentration of matter per unit length. This law is the law of diffusion. The law can be formulated as follows: the flow of particles, which is directed along the axis, is proportional to the derivative of the number of particles with respect to the variable deposited along the axis relative to which the direction of the flow of particles is determined. In other words, the flow of particles moving in the direction of the axis is proportional to the derivative of the number of particles with respect to the variable, which is deposited along the same axis as the flow. Fick's law allows you to describe the process of transfer of matter in time and space.

Diffusion equation

When flows are present in a substance, a redistribution of the substance itself in space occurs. In this regard, there are several equations that describe this redistribution process from a macroscopic point of view. The diffusion equation is differential. It follows from the general equation of matter transfer, which is also called the equation of continuity. In the presence of diffusion, Fick's law is used, which is described above. The equation is as follows:

dn / dt = (d / dx) * (D * (dn / dx) + q.

Diffusion methods

The diffusion method, more precisely the method of its implementation in solid materials, has been widely used recently. This is due to the advantages of the method, one of which is the simplicity of the equipment used and the process itself. The essence of the method of diffusion from solid sources is the deposition of films doped with one or more elements on semiconductors. There are several other methods of diffusion, in addition to the solid source method:

in a closed volume (ampoule method). Minimal toxicity is an advantage of the method, but its high cost, due to the disposable ampoule, is a significant disadvantage;
in an open volume (thermal diffusion). The possibility of using many elements is excluded due to high temperatures, and also side diffusion are the big disadvantages of this method;
in a partially enclosed volume (box method). This is an intermediate method between the two described above.

In order to learn more about the methods and features of diffusion, it is necessary to study additional literature devoted specifically to these issues.

The article shows the role of diffuse processes in wounds sutured in the traditional way and by the method proposed by the authors. Improvement of diffuse processes in wounds during treatment with the device method is theoretically substantiated.

The problem of wound healing of various etiologies is one of the main branches of medicine that have not lost their importance at the present time. Treatment of this pathology in the shortest possible time without purulent complications is possible only with sufficient provision of medical institutions with modern effective wound healing drugs.

In the wound process, the local and general reaction of the body is in direct proportion to the severity and characteristics of damage to tissues and organs. Local and general reactive processes during regeneration processes are in direct and inverse relationship, being interdependent and mutually influencing. Wound treatment is based on the ability to manage the course of the wound process. This problem is invariably in the field of vision of scientists and practicing surgeons.

A large number of applied methods of wound treatment belong to the pharmacological group. At the same time, a large number of technical devices for treating wounds have been proposed. However, the most common wound closure method is the vertical circular suture.

The human skin, consisting of collagen proteins, is an ideal natural membrane that performs numerous metabolic and protective functions. These processes are mainly due to diffusion. Diffusion (from Latin diffusio - spreading, spreading), the mutual penetration of contacting substances into each other due to the movement of particles of matter.

Diffusion is a process at the molecular level and is determined by the random nature of the movement of individual molecules. The diffusion rate is therefore proportional to the average molecular velocity. Diffusion occurs in the direction of a decrease in the concentration of a substance and leads to a uniform distribution of the substance over the entire volume it occupies (to equalization of the chemical potential of the substance).

The role of diffuse processes in the pathogenesis and treatment of the wound process is very great. For example, in skin transplantation, the thickness of the flaps plays a huge role in the healing of burn wounds, since it has a positive effect on diffuse processes between the graft and the wound surface.

However, the significance of diffuse processes in the wound has practically not been studied. The edges of the wound are conductive systems in which diffuse processes should undergo under normal conditions. This process is shown schematically in Figure 1.

The schematic figure shows that the surgical wound (1), sutured with traditional circular vertical sutures according to the classification of A.N. Golikov, has certain disadvantages. Surgical suture (2), which is a means for bringing the wound edges closer together, carries out complete ischemization (5) of tissues, which leads to the formation of "silent areas" for diffusion processes, which leads to deformation (4) of the diffusion vector (3). As a result, the traditionally used surgical suture leads to the artificial formation of tissue regions that are not involved in the regeneration processes. Moreover, in unfavorable cases, these "tissue defects" are the sources of the formation of foci of the infectious process. Because, as a result, the tissue, deprived of access to nutrients, oxygen, etc., necrotizes, which ends with the formation of a scar. Otherwise, necrotic tissue masses are favorable nutrient medium for pathogens.

For the hardware method, a title of protection of the National Institute of Intellectual Property of the Republic of Kazakhstan No. 13864 dated 15.08.2007 was obtained. The main principle of the proposed method is the tight closure of the edges of the wounds to each other using physical and mechanical techniques. Along the edge of the wound, a nylon fishing line of sufficient length is applied, creating a "ligature arc", which is fixed with its ends to the ends of the apparatus of the author's design.

The assembled author's apparatus has the shape of a frame, in the form of a quadrangular parallelogram, the sides of which are rods, and the ends are movable strips located and fixed to the rods by two nuts on both ends of the pins, holes of the same diameter are drilled on the movable strips for the rods and fixing the threads ligatures (Fig. 2).

regeneration processes. The effectiveness of the hardware method has been proven experimentally and clinically.

Thus, it is theoretically proposed to substantiate the effectiveness of the proposed apparatus method in comparison with traditional methods of wound closure. This is due to an increase in pressure on the wound area (due to the design features of the device) leading to a local increase in the diffusion rate.

Literature

Golikov A.N. Healing a granulating wound closed with sutures. - Moscow: 1951. - 160 p.
Waldorf H., Fewres J. Wound healing // Adv. Derm. - 1995. No. 10. - P. 77–96.
Abaturova E.K., Baymatov V.N., Batyrshina G.I. Influence of biostimulants on the wound process // Morphology. - 2002. - T. 121, No. 2–3. - P.6.
Kochnev O.S., Izmailov G.S. Wound closure methods. - Kazan: 1992 .-- 160 p.
Kiselev S.I. The value of donor skin resources in the choice of rational surgical tactics in patients with deep burns: Abstract of the thesis. ... Candidate of Medical Sciences. Ryazan, 1971.17 p.

Zharalardy emdeu biologysyndaғy diffusion

Tuyin Maқalada әdettegi әdispen zhane maқala autorlarymen ұsynylyp otyrғan apparatuses әdistiң zharalardy emdeudegi diffuse processors turaly aytylғyn. Zharalard diffuse processes of the apparatus of әdistiң zhaқsarғany theory zinde dәleldip kөrsetildі.

DIFFUSION INBIOLOGYHealing

Abstract The article shows the role of diffuse processes in wounds sutured in the traditional way and the method proposed by the authors. The diffuse processes in wounds have been justified theoretically.

Esirkepov M.M., Nurmashev B.K., Mukanova U.A.

South Kazakhstan State Medical Academy, Shymkent

Diffusion

An example of diffusion is the mixing of gases (for example, the spread of odors) or liquids (if ink is dropped into the water, then the liquid will become uniformly colored after a while). Another example is related to a solid: the atoms of the contacting metals are mixed at the contact boundary. Particle diffusion plays an important role in plasma physics.

Usually, diffusion is understood as processes accompanied by the transfer of matter, but sometimes other transfer processes are also called diffusion: thermal conductivity, viscous friction, etc.

The diffusion rate depends on many factors. Thus, in the case of a metal rod, thermal diffusion proceeds very quickly. If the rod is made of synthetic material, thermal diffusion is slow. Diffusion of molecules in the general case proceeds even more slowly. For example, if a sugar cube is lowered to the bottom of a glass of water and the water is not stirred, then several weeks will pass before the solution becomes homogeneous. The diffusion of one solid into another occurs even more slowly. For example, if copper is coated with gold, then diffusion of gold into copper will occur, but under normal conditions (room temperature and atmospheric pressure), the gold-bearing layer will reach a thickness of several microns only after several thousand years.

A quantitative description of diffusion processes was given by the German physiologist A. Fick ( English) in 1855

general description

All types of diffusion obey the same laws. The diffusion rate is proportional to the cross-sectional area of the sample, as well as the difference in concentrations, temperatures, or charges (in the case of relatively small values of these parameters). Thus, heat will spread four times faster through a rod with a diameter of two centimeters than through a rod with a diameter of one centimeter. This heat will spread faster if the temperature difference per centimeter is 10 ° C instead of 5 ° C. The diffusion rate is also proportional to the parameter characterizing a particular material. In the case of thermal diffusion, this parameter is called thermal conductivity, in the case of a flow of electric charges - electrical conductivity. The amount of matter that diffuses over a given time and the distance traveled by the diffusing matter are proportional to the square root of the diffusion time.

Diffusion is a process at the molecular level and is determined by the random nature of the movement of individual molecules. The diffusion rate is therefore proportional to the average molecular velocity. In the case of gases, the average velocity of small molecules is higher, namely, it is inversely proportional to the square root of the molecular mass and increases with increasing temperature. Diffusion processes in solids at high temperatures are often found practical use... For example, certain types of cathode ray tubes (CRTs) use metallic thorium diffused through metallic tungsten at 2000 ° C.

If in a mixture of gases the mass of one molecule is four times greater than another, then such a molecule moves twice as slow as compared to its movement in a pure gas. Accordingly, its diffusion rate is also lower. This difference in diffusion rates of light and heavy molecules is used to separate substances with different molecular weights. Isotope separation is an example. If a gas containing two isotopes is passed through a porous membrane, the lighter isotopes penetrate the membrane faster than the heavier ones. For better separation, the process is carried out in several stages. This process was widely used for the separation of uranium isotopes (separation of 235 U from the main mass of 238 U). Since this separation method is energy-intensive, other, more economical separation methods have been developed. For example, the use of thermal diffusion in a gaseous medium is widely developed. A gas containing a mixture of isotopes is placed in a chamber in which a spatial temperature difference (gradient) is maintained. In this case, heavy isotopes eventually concentrate in the cold region.

Fick's equations

From the point of view of thermodynamics, the driving potential of any leveling process is the growth of entropy. At constant pressure and temperature, this potential is played by the chemical potential µ , causing the maintenance of flows of matter. The flux of particles of matter is proportional to the potential gradient

In most practical cases, instead of chemical potential, concentration is used C... Direct replacement µ on the C becomes incorrect in the case of high concentrations, since the chemical potential ceases to be associated with the concentration according to the logarithmic law. If you do not consider such cases, then the above formula can be replaced with the following:

which shows that the substance flux density J proportional to the diffusion coefficient D[()] and concentration gradient. This equation expresses Fick's first law. Fick's second law connects spatial and temporal changes in concentration (diffusion equation):

Diffusion coefficient D depends on the temperature. In some cases, in a wide temperature range, this dependence is the Arrhenius equation.

An additional field applied parallel to the chemical potential gradient violates the steady state. In this case, diffusion processes are described by the nonlinear Fokker-Planck equation. Diffusion processes have great importance in nature:

Nutrition, respiration of animals and plants;
Penetration of oxygen from the blood into human tissue.

Geometric description of the Fick equation

In the second Fick equation, on the left side is the rate of change in concentration over time, and on the right side of the equation is the second partial derivative, which expresses the spatial distribution of concentration, in particular, the convexity of the temperature distribution function projected onto the x axis.

Notes (edit)

Literature

Bokshtein B.S. Atoms wander around the crystal. - M .: Nauka, 1984 .-- 208 p. - (Library "Quant". Issue 28). - 150,000 copies

Links

Diffusion (video tutorial, grade 7 program)
Diffusion of impurity atoms on the surface of a single crystal

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Synonyms:

See what "Diffusion" is in other dictionaries:

- [lat. diffusio spreading, spreading] physical, chem. penetration of molecules of one substance (gas, liquid, solid) into another when they come into direct contact or through a porous partition. Dictionary of foreign words. Komlev N.G., ... ... Dictionary of foreign words of the Russian language

Diffusion- - penetration of particles of one substance into the medium of particles of another substance, which occurs as a result of thermal movement in the direction of decreasing the concentration of another substance. [Bloom E. E. Dictionary of basic metallographic terms. Yekaterinburg … Encyclopedia of terms, definitions and explanations of building materials

Modern encyclopedia

- (from Lat. diffusio spreading spreading, scattering), the movement of particles of the medium, leading to the transfer of matter and equalization of concentrations or to the establishment of an equilibrium distribution of concentrations of particles of a given type in the medium. In the absence of… … Big Encyclopedic Dictionary

DIFFUSION, the movement of a substance in a mixture from an area of high concentration to an area of low concentration, caused by the random movement of individual atoms or molecules. Diffusion stops when the concentration gradient disappears. Speed… … Scientific and technical encyclopedic dictionary

diffusion- and, w. diffusion f., ger. Diffusion lat. diffusio spreading, spreading. Mutual penetration of contacting substances into each other due to the thermal motion of molecules and atoms. Diffusion of gases, liquids. ALS 2. || transfer They… … Historical Dictionary of Russian Gallicisms

Diffusion- (from the Latin diffusio spreading, spreading, scattering), the movement of particles of the medium, leading to the transfer of matter and the equalization of concentrations or the establishment of their equilibrium distribution. Usually diffusion is determined by thermal motion ... ... Illustrated Encyclopedic Dictionary

The movement of particles in the direction of decreasing their concentration, due to thermal motion. D. leads to equalization of the concentrations of the diffusing substance and uniform filling of the volume with particles. ... ... Geological encyclopedia

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Introduction

The relevance of the work. Diffusion is a fundamental natural phenomenon. It underlies the transformations of matter and energy. Its manifestations take place at all levels of organization of natural systems on our planet, from the level of elementary particles, atoms and molecules, and ending with the geosphere. It is widely used in engineering, in Everyday life.

The essence of diffusion is the movement of particles of a medium, leading to the transfer of substances and equalization of concentrations or to the establishment of an equilibrium distribution of particles of a given type in the medium. The diffusion of molecules and atoms is due to their thermal motion.

Diffusion is also a fundamental process underlying the functioning of living systems at any level of organization, from the level of elementary particles (electron diffusion) to the biosphere level (circulation of substances in the biosphere).

It plays a huge role in nature, in human life and technology. Diffusion processes can have both positive and negative effects on the vital activity of humans and animals. An example of a positive impact is the maintenance of a uniform composition of atmospheric air near the Earth's surface. Diffusion plays an important role in various fields of science and technology, in processes occurring in animate and inanimate nature. It influences the course of chemical reactions.

With the participation of diffusion or with the violation and change of this process, negative phenomena can occur in nature and human life, such as extensive pollution of the environment with products of human technological progress.

Objective: Investigate the features of diffusion in gases, liquids and solids and find out the use of diffusion by humans and the manifestation of diffusion in nature, consider the influence of diffusion processes on the ecological balance in nature and the influence of humans on diffusion processes.

The essence of diffusion

Demonstrates diffusion in gases by spraying deodorant in the corner of the classroom. The spread of the smell is explained by the movement of molecules. This movement is continuous and disorderly. Colliding with the molecules of gases that make up the air, the molecules of the deodorant change their direction of movement many times and, randomly moving, scatter throughout the room.

The process of penetration of particles (molecules, atoms, ions) of one substance between particles of another substance due to chaotic movement is called diffusion(from Latin diffusio - spreading, spreading, dispersing). Thus, diffusion is the result of the chaotic movement of all particles of a substance, of any mechanical action.

The movements of particles during diffusion are completely random, all directions of displacement are equally probable,

Since particles move in gases, liquids, and solids, diffusion is possible in these substances. Diffusion is the transfer of matter caused by the spontaneous equalization of an inhomogeneous concentration of atoms or molecules of different types. If portions of various gases are admitted into the vessel, then after a while all gases are uniformly mixed: the number of molecules of each type in a unit volume of the vessel will become constant, the concentration is leveled. Diffusion is explained as follows. First, the interface between the two media is clearly visible between the two bodies (Fig. 1a). Then, due to their movement, individual particles of substances located near the border exchange places.

The boundary between substances is blurring (Fig. 1b). Having penetrated between the particles of another substance, the particles of the first begin to exchange places with the particles of the second, which are in ever deeper layers. The interface between substances becomes even more vague. Due to the continuous and disordered movement of particles, this process ultimately leads to the fact that the solution in the vessel becomes homogeneous (Fig. 1c).

Fig. 1. Explanation of the phenomenon of diffusion.

Diffusion in nature

With the help of diffusion, various gaseous substances spread in the air: for example, the smoke of a fire spreads over long distances.

The result of this phenomenon can be an equalization of the temperature in the room during ventilation. In the same way, air pollution with harmful industrial products and exhaust gases from cars occurs. The natural combustible gas we use at home is colorless and odorless. When a leak occurs, it is impossible to notice it, therefore, at distribution stations, the gas is mixed with a special substance that has a pungent, unpleasant odor that is easily felt by humans.

Due to the phenomenon of diffusion, the lower layer of the atmosphere - the troposphere - consists of a mixture of gases: nitrogen, oxygen, carbon dioxide and water vapor. In the absence of diffusion, stratification would occur under the action of gravity: a layer of heavy carbon dioxide would appear below, oxygen would be above it, and inert gases would be nitrogen above it.

We also observe this phenomenon in the sky. Scattering clouds are also an example of diffusion, and as F. Tyutchev says exactly about this: "Clouds are melting in the sky ..."

In liquids, diffusion proceeds more slowly than in gases, but this process can be accelerated by heating. For example, in order to quickly pickle cucumbers, they are poured with hot brine. We know that sugar will dissolve more slowly in cold tea than in hot tea.

In the summer, watching the ants, I always wondered how they, in a huge world for them, would recognize their way home. It turns out that the phenomenon of diffusion opens this riddle. Ants mark their path with droplets of odorous liquid.

Through diffusion, insects find food for themselves. Butterflies, fluttering between plants, always find their way to a beautiful flower. The bees, having discovered a sweet object, storm it with their swarm.

And the plant grows, blooms for them, too, thanks to diffusion. After all, we say that the plant breathes and exhales air, drinks water, receives various micro-additives from the soil.

Carnivores also find their prey through diffusion. Sharks smell blood at a distance of several kilometers, just like piranha fish.

The ecology of the environment is deteriorating due to emissions of chemical and other harmful substances into the atmosphere, into water, and all this spreads and pollutes vast territories. Trees, on the other hand, release oxygen and absorb carbon dioxide through diffusion.

Mixing is based on the diffusion principle fresh water with salty at the confluence of rivers into the sea. Diffusion of solutions of various salts in the soil contributes to the normal nutrition of plants.

In all the above examples, we observe the mutual penetration of molecules of substances, i.e. diffusion. Many physiological processes in humans and animals are based on this process: such as respiration, absorption, etc. In general, diffusion is of great importance in nature, but this phenomenon is also harmful in relation to environmental pollution.

2.1 Diffusion in the plant kingdom

K.A. Timiryazev said: “Are we going to talk about feeding the root at the expense of substances in the soil, whether we are going to talk about the air feeding of leaves through the atmosphere or feeding one organ at the expense of another, neighboring? : diffusion ".

Indeed, diffusion plays a very important role in the plant world. For example, the great development of the leaf crown of trees is explained by the fact that diffusion exchange through the surface of the leaves performs not only the function of respiration, but partly also of nutrition. Currently, foliar feeding of fruit trees by spraying their crowns is widely practiced.

Diffuse processes play an important role in the supply of natural reservoirs and aquariums with oxygen. Oxygen enters the deeper layers of water in stagnant waters due to diffusion through their free surface. Therefore, any restrictions on the free surface of the water are undesirable. So, for example, leaves or duckweed covering the surface of the water can completely stop the access of oxygen to the water and lead to the death of its inhabitants. For the same reason, narrow-necked vessels are not suitable for use as an aquarium.

In the process of metabolism, when complex nutrients or their elements are broken down into simpler ones, the energy necessary for the vital activity of the body is released.

2.2 The role of diffusion in plant nutrition.

The main role in diffusion processes in living organisms is played by cell membranes, which have selective permeability. The passage of substances through the membrane depends on:

The size of the molecules;

Electric charge;

On the presence and number of water molecules;

From the solubility of these particles in fats;

From the structure of the membrane.

There are two forms of diffusion: a) dialysis- this is the diffusion of solute molecules; b) osmosis is the diffusion of a solvent through a semipermeable membrane. Soil solutions contain mineral salts and organic compounds... Water from the soil enters the plant by osmosis through the semipermeable membranes of root hairs. The concentration of water in the soil turns out to be higher than inside the root hairs; therefore, diffusion occurs from the zone with a higher concentration to the zone with a lower concentration. Then the concentration of water in these cells becomes higher than in the overlying ones - a root pressure arises, causing an upward flow of juice along the roots and stem, and the loss of water by the leaves ensures further absorption of water.

Mineral substances enter the plant: a) by diffusion; b) sometimes by active transfer against the concentration gradient, accompanied by energy expenditure. Distinguish also turgor pressure- This is the pressure exerted by the contents of the cell on the cell wall. It is almost always below the osmotic pressure of the sap cell, because the outside is not pure water, but a saline solution. Turgor pressure value:

Preservation of the shape of the plant organism;

Ensuring growth in young plant cells;

Preservation of the firmness of plants (demonstration of cactus and aloe plants);

Shaping in the absence of reinforcing fabric (demonstration of a tomato);

The use of diffusion in medicine.

More than 30 years ago, the German physician William Kolff used the "artificial kidney" apparatus. Since then, it has been used: for emergency chronic care in acute intoxication; to prepare patients with chronic renal failure for kidney transplantation; for long-term (10-15 years) life support of patients with chronic kidney disease.

The use of the "artificial kidney" apparatus is becoming more of a therapeutic procedure, the apparatus is used both in the clinic and at home. The device was used to prepare the recipient for the world's first successful kidney transplantation, carried out in 1965 by academician B.V. Petrovsky.

The device is a hemodialyzer in which blood comes into contact with a saline solution through a semipermeable membrane. Due to the difference in osmotic pressure from the blood into the saline solution, ions and molecules of metabolic products (urea, uric acid), as well as various toxic substances to be removed from the body, pass through the membrane. The device is a system of flat channels, separated by thin cellophane membranes, through which blood and dialysate slowly move in countercurrents - a saline solution enriched with a gas mixture of CO 2 + O 2 The device is connected to the patient's circulatory system using catheters inserted into the hollow into dialysate) and ulnar (outlet) veins. Dialysis lasts 4-6 hours. This achieves blood purification from nitrogenous toxins with insufficient renal function, ie. regulation of the chemical composition of blood is carried out.

Biology teacher: The following message will help you to understand and understand the forms of diffusion, osmosis and dialysis.

The use of diffusion in technology and in everyday life

Diffusion is widely used in industry and everyday life. Diffusion welding of metals is based on the phenomenon of diffusion. Metals, non-metals, metals and non-metals, plastics are connected by diffusion welding without the use of solders, electrodes and fluxes. The parts are placed in a closed welding chamber with a strong vacuum, squeezed and heated to 800 degrees. In this case, there is an intense mutual diffusion of atoms in the surface layers of the contacting materials. Diffusion welding is mainly used in the electronic and semiconductor industries, precision engineering.

A diffusion apparatus is used to extract soluble substances from the crushed solid material. Such devices are used mainly in the sugar beet industry, where they are used to obtain sugar juice from beet chips heated together with water.

An essential role in the operation of nuclear reactors is played by neutron diffusion, that is, the propagation of neutrons in matter, accompanied by multiple changes in the direction and speed of their movement as a result of collisions with atomic nuclei. The diffusion of neutrons in a medium is similar to the diffusion of atoms and molecules in gases and obeys the same laws.

As a result of the diffusion of carriers in semiconductors, an electric current arises. The movement of charge carriers in semiconductors is due to the inhomogeneity of their concentration. To create, for example, a semiconductor diode, indium is fused into one of the surfaces of germanium. Due to the diffusion of indium atoms deep into the germanium single crystal, a pn junction is formed in it, through which a significant current can flow with minimal resistance.

The process of metallization is based on the phenomenon of diffusion - coating the surface of an article with a layer of metal or alloy to impart physical, chemical and mechanical properties to it, which are different from those of the material being metallized. It is used to protect products from corrosion, wear, increase contact electrical conductivity, for decorative purposes, so, to increase the hardness and heat resistance of steel parts, carburizing is used. It consists in the fact that steel parts are placed in a box with graphite powder, which is installed in a thermal furnace. Due to diffusion, carbon atoms penetrate into the surface layer of parts. The penetration depth depends on the temperature and the holding time of the parts in the thermal oven.

Human influence on the course of diffusion in nature.

Unfortunately, as a result of the development of human civilization, there is a negative impact on nature and the processes taking place in it. The diffusion process plays an important role in the pollution of rivers, seas and oceans. For example, you can be sure that detergents poured down the drain, for example, in Odessa, will end up off the coast of Turkey due to diffusion and existing currents. The annual discharge of industrial and domestic wastewater in the world is estimated at tens of trillions of tons. An example of the negative influence of man on diffusion processes in nature is large-scale accidents that occurred in the basins of different water bodies. As a result of this phenomenon, oil and products of its processing spread over the surface of the water and, as a result, diffusion processes are disrupted, for example: oxygen does not enter the water column, and fish die without oxygen.

Due to the phenomenon of diffusion, the air is polluted with wastes from different factories, because of it, harmful human waste penetrates into the soil, water, and then has a harmful effect on the life and functioning of animals and plants. The area of land polluted by industrial emissions, etc. is increasing. More than 2 thousand hectares of land are occupied by dumps of industrial and domestic waste. One of the issues that are difficult to solve at the present time is the issue of disposal of industrial waste, including toxic.

An urgent problem is air pollution from exhaust gases, products of processing harmful substances emitted into the atmosphere by various factories. Chimneys of enterprises emit carbon dioxide, nitrogen oxides and sulfur into the atmosphere. At present, the total amount of gas emissions into the atmosphere exceeds 40 billion tons per year. An excess of carbon dioxide in the atmosphere is dangerous for the living world of the Earth, disrupts the carbon cycle in nature, and leads to the formation of acid rain. The diffusion process plays a large role in the pollution of rivers, seas and oceans. The annual discharge of industrial and domestic wastewater in the world is approximately 10 trillion tons.

Several medical studies have shown a relationship between the incidence of respiratory and upper respiratory tract diseases and the state of the air. There is a direct relationship between the rate of respiratory diseases and the volume of emissions of harmful substances into the atmosphere. The listed examples of diffusion have a harmful effect on various processes occurring in nature.

Pollution of water bodies leads to the disappearance of life in them, and the water used for drinking has to be purified, which is very expensive. In addition, chemical reactions with the release of heat occur in polluted water. The water temperature rises, while the oxygen content in the water decreases, which is bad for aquatic organisms. Due to the rise in water temperature, many rivers now do not freeze in winter. To reduce the emission of harmful gases from industrial pipes, pipes of thermal power plants, special filters are installed. Such filters are installed, for example, at a thermal power plant in the Leninsky district of Chelyabinsk, but their installation is very expensive. To prevent pollution of water bodies, it is necessary to ensure that garbage, food waste, manure are not thrown near the banks, different kinds chemicals.

Considering global warming, it is important to investigate the change in the diffusion rate depending on the increase in the ambient temperature.

Experimental part.

I experience. Observation of the penetration of particles of one substance between the molecules of another substance .

Target : study the diffusion of solids and make a conclusion about the rate of diffusion.

Devices and materials : gelatin, potassium permanganate, copper sulfate, Petri dish, tweezers, heating device.

Gelatin serves as a solid solution. In order to prepare the solution, it is necessary to put 1 spoon of gelatin in cold water for 2 hours so that the powder swells, then heat the mixture and dissolve the gelatin without boiling, then pour it into a Petri dish (Fig. 3). When the gelatin cooled down, a crystal of potassium permanganate was brought into the middle with a quick movement with tweezers, and a crystal of potassium permanganate into the other glass, and now we can observe the result of diffusion.

Here we observed the penetration of potassium permanganate and copper sulfate particles between the gelatin molecules. After 24 hours, it was observed that the diffusion of potassium permanganate did not occur (Fig. 4), since potassium permanganate is a strong oxidizing agent.

Thus, diffusion in solids proceeds more slowly. If strong oxidants enter the environment, they lead to its destruction.

II experiment. Observation of the dissolution of gouache pieces in water, at a constant temperature (at t = 22 ° C)

We took a piece of orange gouache and a vessel with clean water at a temperature of 22 ° C. They put a piece of gouache into the vessel (Fig. 1) and began to observe what was happening. After 10 minutes, the water in the vessel begins to color in the color of a gouache (solid) (Fig. 2). Water is a good solvent. Under the action of water molecules, the bonds between the molecules of gouache solids are destroyed. 25 minutes have passed since the start of the experiment. The color of the water becomes more intense (Fig. 3). Water molecules penetrate between the gouache molecules, breaking the forces of attraction. 45 minutes have passed since the beginning of the experiment (Fig. 4). Simultaneously with the forces of attraction between the molecules, repulsive forces begin to act and, as a result, the crystal lattice of the solid (gouache) is destroyed. The process of dissolving the gouache is over. The experiment took 2 hours and 50 minutes. The water is completely gouache-colored.

Thus, the phenomenon of diffusion is a long-term process, as a result of which the dissolution of solids occurs.

Experience.Study of the dependence of the rate of diffusion on temperature and penetration into food.

Target : study how temperature affects the rate of diffusion.

Devices and materials : thermometers - 2 pieces, watches - 1 piece, glass - 1 piece, iodine, potatoes, magnetic stirrer.

Description of the experience and the results obtained : took a glass, placed iodine in it and closed the glass with potatoes cut in half at t = 22 ° C. After 15 minutes from the beginning of the experiment, the diffusion process is inactive. The heating process was started after 4 minutes. The diffusion process started, after 1 min, we see the penetration of iodine into the potatoes, after 2 min.

From this experience, it can be concluded that the rate of diffusion is influenced by temperature: the higher the temperature, the higher the rate of diffusion, which negatively affects food.

Thus, the air is polluted with wastes from different factories, the exhaust gases of cars penetrate into food, and then have a harmful effect on the life and functioning of humans, animals and plants.

IV experience.Study of the dependence of the rate of diffusion of gaseous substances into water at a constant temperature

Target : study the rate of diffusion of gaseous substances into water at a constant temperature and draw a conclusion about the rate of diffusion.

Devices and materials : thermometers - 1 pc, clock - 1 pc, flask - 1 pc, water, iodine.

Description of the experience and the results obtained : water of the same mass and the same temperature (22 ° С) was poured into the flask, then vegetable oil (5 ml) was poured into another flask. The vegetable oil in our experiment mimicked oil. The flasks were closed with scotch tape with iodine glued to it. The observation was removed after 45 minutes.

The water, covered with a film of vegetable oil, is very weakly colored, then it can be judged that it is more difficult for oxygen molecules to penetrate into the water: fish and other aquatic inhabitants lack oxygen and may even die.

Conclusion : the presence of various substances on the water surface disrupts diffusion processes and can lead to undesirable environmental consequences.

Conclusion

We see how great the significance of diffusion in inanimate nature is, and the existence of living organisms would be impossible if it were not for this phenomenon. Unfortunately, we have to deal with the negative manifestation of this phenomenon, but there are much more positive factors, and therefore we are talking about the enormous importance of diffusion in nature.

Nature makes extensive use of the possibilities inherent in the process of diffusional penetration, plays an essential role in the absorption of food and oxygenation of the blood. In the flame of the Sun, in the life and death of distant stars, in the air we breathe, everywhere we see the manifestation of an omnipotent and universal diffusion.

Thus, diffusion is of great importance in the life processes of humans, animals and plants. Due to diffusion, oxygen from the lungs penetrates into the human blood, and from the blood - into the tissues. But, unfortunately, as a result of their activities, people often have a negative impact on natural processes in nature.

Studying diffusion, its role in the ecological balance of nature and the factors influencing its flow in nature, I came to the conclusion that it is necessary to draw public attention to environmental problems.

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