Emale paint dispersed medium and phase. Dispersed systems: definition, classification

27.04.2021

Dispersed systems

Clean substances in nature are very rare. Mixtures of different substances in various aggregate states can form heterogeneous and homogeneous systems - dispersed systems and solutions.
Dispersed They call heterogeneous systems in which one substance in the form of very small particles is evenly distributed in the volume of the other.
Then the substance that is present in smaller quantities and is distributed in the volume of the other, called dispersed phase . It may consist of several substances.
The substance present in greater quantities in the amount of which the dispersed phase is distributed, called dispersion environment . Between it and the particles of the dispersed phase there is a section of the section, so the dispersed systems are called heterogeneous (inhomogeneous).
Both the dispersion medium and the dispersed phase can be substances that are in various aggregate states - solid, liquid and gaseous.
Depending on the combination of the aggregate state of the dispersion medium and the dispersed phase, 9 species of such systems can be distinguished.

The magnitude of the particles of substances constituting the dispersed phase, the dispersed systems are divided into coarse (suspension) with particle sizes of more than 100 nm and fine-dispersed (colloidal solutions or colloidal systems) with particle sizes from 100 to 1 nm. If the substance is fragmented to molecules or ions of less than 1 nm, a homogeneous system is formed - the solution. It is homogeneous (homogeneous), the surface of the section between particles and the medium is not.

Already a quick acquaintance with dispersed systems and solutions shows how important they are in everyday life and in nature.

Judge for yourself: without Nilsk, the Great Civilization of Ancient Egypt would not take place; Without water, air, rocks and minerals at all, there would be no living planet - our common house - Earth; No cells would not have live organisms, etc.

Classification of dispersed systems and solutions

Suspend

Suspend - These are dispersed systems in which the particle size of the phase is more than 100 nm. These are opaque systems, separate particles of which can be noticed by the naked eye. The dispersed phase and the dispersion medium are easily divided by upholding. Such systems are divided into:
1) emulsions (and medium, and phase are insoluble in each other fluid). These are well-known milk, lymph, waterfront paints, etc.;
2) suspension (medium - liquid, and the phase is an insoluble solid in it). These are building solutions (for example, "lime milk" for blissing), weighted in water river and sea silf, lively suspension of microscopic living organisms in sea water - plankton, which feed the giants-whales, and so on;
3) aerosols - suspension in gas (for example, in the air) of small particles of liquids or solids. Distinguish dust, smoke, fog. The first two types of aerosols are suspension of solid particles in a gas (larger particles in dust), the latter - the suspension of small droplets of the liquid in the gas. For example, natural aerosols: fog, thunderstorm clouds - suspend in the air of water droplets, smoke - small solid particles. A was able to hang over the largest cities of the world, also an aerosol with a solid and liquid dispersed phase. Residents of settlements near cement factories suffer from the thinner of the subtlest cement dust, which is generated during the grinding of cement raw materials and the product of its firing - clinker. Similar harmful aerosols - dust - are also in cities with metallurgical production. Smoke factory pipes, smsi, the smallest droplets of saliva, departing from the mouth of the patient with the flu, also harmful aerosols.
Aerosols play an important role in nature, everyday life and human production activities. Clouds clusters, processing of fields of chemicals, applying paintworks with a pulverizer, spraying fuels, production of dry dairy products, treatment of respiratory tract (inhalation) - examples of those phenomena and processes where aerosols benefit. The aerosols are fogs over the sea, near the waterfalls and fountains, the rainbow arising in them delivers a man joy, aesthetic pleasure.
For chemistry, dispersed systems are most important in which the medium is water and liquid solutions.
Natural water always contains dissolved substances. Natural aqueous solutions are involved in the process of soil formation and supply plant with nutrients. The complex processes of vital activity occurring in human and animal organisms also flow in solutions. Many technological processes in the chemical and other industries, such as the preparation of acids, metals, paper, soda, fertilizers, flow in solutions.

Colloid Systems

Colloid Systems - These are such dispersed systems in which the particle size of the phase from 100 to 1 nm. These particles are not visible to the naked eye, and the dispersed phase and the dispersion medium in such systems upholding are separated by difficulty.
They are divided into evil (colloidal solutions) and gels (jelly).
1. Colloidal solutions, or evil. This is the majority of liquids of the living cell (cytoplasm, nuclear juice - karyoplasm, the contents of organoids and vacuoles) and the living organism as a whole (blood, lymph, tissue liquid, digestive juices, humoral fluids, etc.). Such systems form adhesives, starch, proteins, some polymers.
Colloidal solutions can be obtained as a result of chemical reactions; For example, when the solutions of potassium silicates or sodium ("soluble glass") with acid solutions are formed by a colloid solution of silicic acid. The sol formed in the hydrolysis of iron chloride (W) in hot water. Colloidal solutions are externally similar to true solutions. They are distinguished from the latter by the resulting "luminous path" - a cone when passing through them the beam of light.

This phenomenon is called the effect of Tyndle . Large than in a true solution, particles of the dispersed phase of sol reflect the light from its surface, and the observer sees a glowing cone in a vessel with a colloidal solution. In a true solution, it is not formed. A similar effect, but only for an aerosol, not a liquid colloid, you can observe in cinemas when the ray of light from the film preparation through the air of the cinema hall.

Coagulation - The phenomenon of sticking of colloidal particles and precipitate them is observed when neutralizing the charges of these particles, when electrolyte is added to the colloidal solution. In this case, the solution turns into a suspension or gel. Some organic colloids are coagulated when heated (glue, egg protein) or with a change in the acid-alkaline environment of the solution.

2. Gels , or jelly, which are pupils formed during the coagulation of asses. These include a large number of polymeric gels, so well-known pastry shops, cosmetic and medical gels (gelatin, keel, jelly, marmalade, cake "Bird's milk") and of course an infinite set of natural gels: minerals (opal), body jellyfish, cartilage , tendons, hair, muscle and nervous fabric, etc. The history of the development of life on Earth can be simultaneously considered the history of the evolution of the colloidal state of the substance. Over time, the structure of the gels is broken - water is distinguished from them. This phenomenon is called sinieresis. .

Solutions

Called solution Homogeneous system consisting of two or more substances.
The solutions are always single-phase, that is, they are homogeneous gas, liquid or solid. This is due to the fact that one of the substances is distributed in the mass of the other in the form of molecules, atoms or ions (particle size of less than 1 nm).
Solutions are called true If required to emphasize their difference from colloidal solutions.
The solvent is considered to be a substance that the aggregate state of which does not change in the formation of the solution. For example, water in aqueous solutions of cook salt, sugar, carbon dioxide. If the solution was formed when mixing gas with gas, liquid with liquid and solid with a solid, the solvent is considered to be the component that is larger in solution. So, air is a solution of oxygen, noble gases, carbon dioxide in nitrogen (solvent). Table vinegar, which contains from 5 to 9% acetic acid, is a solution of this acid in water (solvent - water). But in acetic essence, acetic acid plays the role of the solvent, since its mass fraction is 70-80%, therefore, this is a solution of water in acetic acid.

When crystallizing the liquid alloy of silver and gold, solid solutions of different compositions can be obtained.
Solutions are divided into:
molecular - these are aqueous solutions of non-electrolyte - organic substances (alcohol, glucose, sucrose, etc.);
molecular-ionic - these are solutions of weak electrolytes (nitrogenous, hydrogen sulfide acids, etc.);
ionic are solutions of strong electrolytes (alkalis, salts, acids - NaOH, K 2 S0 4, HN0 3, NS1O 4).
Previously, there were two points of view on the nature of dissolution and solutions: physical and chemical. According to the first solutions, they were considered mechanical mixtures, according to the second - as unstable chemical compounds of the particles of a dissolved substance with water or another solvent. The last theory was expressed in 1887 by D. I. Mendeleev, who devoted to the study of solutions for more than 40 years. Modern chemistry considers dissolution as a physicochemical process, and solutions as physicochemical systems.
A more accurate determination of the solution is:
Solution - homogeneous (homogeneous) system consisting of particles of a dissolved substance, solvent and products of their interaction.

The behavior and properties of electrolyte solutions, as you know well, explains the other most important theory of chemistry - the theory of electrolytic dissociation, developed by S. Arrhenius, developed and supplemented by students by D. I. Mendeleev, and first of all I. A. Helukov.

Questions for fixing:
1. What are dispersed systems?
2. When skin damage (wound), blood coagulation is observed - the coagulation of the Zol. What is the essence of this process? Why does this phenomenon perform a protective function for the body? What is the name of the disease in which blood coagulation is difficult or not observed?
3. Tell us about the meaning of various dispersed systems in everyday life.
4. Make the evolution of colloidal systems in the process of life development on Earth.

In nature, there are no elements that would be clean. At the heart of their own, they are all different mixtures. They, in turn, can be heterogeneous or homogeneous. Food from substances in an aggregate state, while creating a specific dispersion system in which various phases are present. In addition, in the mixtures there is usually a dispersion environment. Its essence is that it is considered an element with a large volume in which any substance is distributed. In the dispersed system, the phase and medium are located in such a way that the parties of the section surface were between them. Therefore, it is called heterogeneous or inhomogeneous. In view of this, the effect of the surface, and not particles as a whole, has a huge meaning.

Classification of the dispersed system

The phase is known to represent substances having a different state. And these elements are divided into several types. The aggregate state of the dispersed phase depends on the combination of the medium in it, the result is 9 types of systems:

Gas. Liquid, solid and element in question. Homogeneous mixture, fog, dust, aerosols.
Liquid dispersed phase. Gas, solid, water. Foam, emulsion, evil.
Solid dispersed phase. Liquid, gas and the substance considered in this case. Soil, medicine in medicine or cosmetics, rocks.

As a rule, the dimensions of the dispersed system are determined by the magnitude of the phase particles. There is the following classification:

coarse (suspended);
thin and true).

Dispersion particles

After analyzing the coarse mixtures, it is possible to move that the particles of these compounds in the structure can be noticeable to the naked eye, due to the fact that their size is more than 100 nm. The suspension, as a rule, belong to the system in which the dispersed phase is separated from the medium. This is because they are considered opaque. The suspension is divided into emulsions (insoluble liquids), aerosols (small particles and solids), suspension (solid in water).

The colloidal substance is any, which has the quality that another element is evenly dispersed on it. That is, it is present, and more precisely is part of the dispersed phase. This state is when one material is fully distributed in the other, or rather in its volume. In an example with milk, liquid fat is scattered in an aqueous solution. In this case, a smaller molecule is within 1 nanometer and 1 micrometer, which makes it invisible to an optical microscope when the mixture becomes homogeneous.

That is, no part of the solution has a greater or smaller concentration of the dispersed phase than any other. It can be said that he is colloid in nature. The larger is called a solid phase or dispersion medium. Since its size and distribution do not change, and the element in question is distributed over it. Types of colloids include aerosols, emulsions, foam, dispersion and mixtures, called hydrosols. Each such system has two phases: dispersed and continuous phase.

Colloids in history

Intensive interest in such substances was present in all sciences at the beginning of the 20th century. Einstein and other scientists carefully studied their characteristics and applications. At that time, this new science area was the leading area of \u200b\u200bresearch for theorists, researchers and manufacturers. After the peak of interest until 1950, the study of colloids significantly decreased. It is interesting to note that with the recent nucleation of more highly powerful microscopes and nanotechnologies (the study of objects of a certain tiny scale), scientific interest in the study of new materials is again increasing.

More about these substances

There are elements observed both in nature and in artificial solutions with colloidal properties. For example, mayonnaise, cosmetic lotion and lubricants are types of artificial emulsions, and milk is a similar mixture that occurs in nature. Colloid foams include whipped cream and shaving foam, while edible elements include oil, marshmallow and jelly. In addition to food, these substances exist in the form of some alloys, paints, ink, detergents, insecticides, aerosols, polystyrene foam and rubber. Even beautiful natural objects, such as clouds, pearls and opals, possess colloidal properties, because they have a different substance that is evenly distributed through them.

Obtaining colloidal mixtures

Increasing small molecules up to a range from 1 to 1 micrometer, or by reducing large particles to the same size. Colloidal substances can be obtained. Further production depends on the type of elements used in the dispersed and continuous phases. Colloids behave differently than ordinary liquids. And this is observed in transport and physicochemical properties. For example, the membrane may allow a true solution with solid molecules attached to liquid, pass through it. While the colloidal substance that has a solid, dispersed through the liquid, will stretch the membrane. The parity of the distribution is homogeneous to the point of microscopic equality in the interval throughout the second element.

True solutions

Colloid dispersion has a representation in the form of a homogeneous mixture. The element consists of two systems: continuous and dispersed phase. This indicates that this case is associated with because they are directly related to the above mixture consisting of several substances. In the colloid, the second has the structure of the smallest particles or droplets, which are evenly distributed in the first. From 1 nm to 100 nm is the size of the dispersed phase, or rather particles at least in one dimension. In this range, the dispersed phase is with the specified dimensions you can call the exemplary elements suitable for the description: colloidal aerosols, emulsions, foam, hydrosolis. Surrounded by the chemical composition of the surface largely particle or drops present in the compositions under consideration.

Colloidal solutions and systems

It should be taken into account the fact that the size of the dispersed phase is a difficult variable in the system. Solutions are sometimes characterized by their own properties. To make it easier to perceive the indicators of the compositions, the colloids are reminded and look almost the same. For example, if it is dispersed in a liquid, solid shape. As a result, particles will not pass through the membrane. At the time when other components like dissolved ions or molecules are able to pass through it. If analyzing it easier, it turns out that the dissolved components pass through the membrane, and the colloid particles will not be able to do with the phase under consideration.

Appearance and disappearance of color characteristics

Due to the effect of Tyndal, some similar substances are translucent. In the structure of the element, it is the scattering of light. Other systems and compositions are with some touch or at all to be opaque, with a certain color, let some even with non-market. Many familiar substances, including oil, milk, cream, aerosols (fog, smoke), asphalt, paints, paints, glue and sea foam, are colloids. This area of \u200b\u200bstudy was introduced in 1861 by the Scottish scientist Thomas Gram. In some cases, the colloid can be considered as a homogeneous (non-heterogeneous) mixture. This is due to the fact that the difference between "dissolved" and "grain" substance can sometimes be subject to approach.

Hydrocoleloid types of substances

This component is defined as a colloid system in which particles are dispersed in water. Hydrocoleloid elements depending on the amount of fluid can take various states, such as gel or sol. There are irreversible (single) or reversible. For example, agar, second type of hydrocolloid. It may exist in a state of gel and sol, and alternate between states with the addition or removal of heat.

Many hydrocolloids are obtained from natural sources. For example, Carragegen is extracted from algae, gelatin has bovine fat, and pectin from citrus and apple cake peat. Hydrocolloids are used in food products mainly to affect texture or viscosity (sauce). Also used to care for the skin or as a healing means after injury.

Essential characteristics of colloidal systems

This information shows that colloidal systems are a dispersion subsection. They, in turn, can be solutions (soles) or gels (jelly). The first in most cases are created on the basis of living chemistry. The second are formed under the sediments, which occur in the coagulation process of asses. Solutions can be aqueous with organic substances, weak or strong electrolytes. The dimensions of the particles of the dispersed phase of colloids from 100 to 1 nm. They cannot be seen with the naked eye. As a result of settling the phase and the medium it is difficult to divide.

Classification by type of particles of the dispersed phase

Multi-molecular colloids. When, when dissolved, atoms or smaller molecules of substances (having a diameter of less than 1 nm) are combined together to form particles of such dimensions. In these ash, the dispersed phase is a structure that consists of aggregates of atoms or molecules with a molecular size of less than 1 nm. For example, gold and sulfur. These are held together by Van der Waals. They usually have a lyophilic nature. This means a significant interaction of particles.

High molecular colloids. These are substances having a large-size molecules (so-called macromolecules), which, when dissolved, form a certain diameter. Such substances are called macromolecular colloids. These elements forming the dispersed phase are usually polymers having very high molecular weights. Natural macromolecules are starch, cellulose, proteins, enzymes, gelatin, etc. Artificial includes synthetic polymers, such as nylon, polyethylene, plastics, polystyrene, etc. They are usually foaming, which means weak interaction in this case. Particles.

Related colloids. These are substances that, when dissolved in the medium, behave as normal electrolytes at low concentration. But colloidal particles are made with greater enzyme components due to the formation of aggregated elements. The particles formed in this way are called micelles. Their molecules contain both lyophilic and liquophobic groups.

Micelles. Conduct cluster or aggregated particles formed by the colloid association in solution. Conventional examples are soaps and detergents. Education occurs above a certain temperature of the craft, and above a certain critical concentration of micelling. They are capable of forming ions. Micelles may contain up to 100 molecules and more, for example, sodium stearate is a typical example. When it dissolves in water, it gives ions.

§ 14. Dispersed systems

Clean substances in nature are veryseldom. Mixtures of various substances in different aggregatestates can form heterogeneous and homogene systems - dispersed systems and solutions.

Dispersed Call heterogeneous systems , in which one substance in the form of very small chasteits is evenly distributed in the volume of the other.

Then substance (or several substances), whichpresent in the disperse system in a smallercessing and distributed in volume, calleddispersnoy Phase . Present in Blassy Quantitysubstance, in the amount of which dispersesphase called dispersion environment . Betweendispersion medium and particles of the dispersed phasethere is a surface of the section, it is precisely audible systems called heterogeneous. inhomogeneous.
And the dispersion medium, and the dispersed phase can be substances that are in various aggregate states. Depending on the combination of the states of the dispersion medium and the dispersed phase, eight types of such systems can be distinguished (Table 2).
table 2

Classification of dispersed systems
by aggregative state

Dispersion naya Environment	Dispers naya Phase	Examples of some natural and domestic dispersed systems
Gas	Liquid	Fog, passing gas with oil droplets, carburetor mixture in engine engines bile (droplets of ben- zina in the air)
Gas	Hard substance	Dust in the air smoke, smiling, samum (dust and sandy storm)
Liquid	Gas	Swiming drinks foam in the bath
	Liquid	Liquid media bottom (blood plasma, lymph, digestive liquid juices), liquid content cells (cytoplasm, caroi plasma)
	Hard substance	Kissel, jelly, adhesives, weighted in water river or marine il, construction creators
Hard substance	Gas	Snow-in-eyed syrov air B. it, soil, textiles tissue, brick and ceramics, foam porous chocolate, powders
	Liquid	Wet soil, media qing and cosmetic means (ointment, mascara, lipstick, etc.)
	Hard substance	Rocks, color glass, some alloys

By the magnitude of the particles of the substance constituting the dispersed phase, the dispersed systems are divided into coarse particles with a particle size of more than 100 nm and fine-dispersed with particle sizes from 1 to 100 nm. If the substance is fragmented to molecules or ions of less than 1 nm, a homogeneous system is formed - the solution. The solution is homogeneous, the surface of the section between particles and the medium is not, and therefore it does not apply to dispersed systems.

Acquaintance with dispersed systems and solutions shows how important they are in everyday life and nature. Judge for yourself: the great civilization of the ancient Egypt would not take place without Nilsky El (Fig. 15); Without water, air, rocks, minerals at all, there would be no living planet - our common house - Earth; No cells would not have live organisms.

Fig. 15. Flames of the Nile and the history of civilization
The classification of dispersed systems and solutions depending on the size of the phase particles is given in Scheme 1.
Scheme 1.
Classification of dispersed systems and solutions

Mountain systems. The coarse systems are divided into three groups: emulsions, suspensions and aerosols.

Emulsions - These are dispersed systems with a liquid dispersion medium and a liquid dispersed phase.

They can also be divided into two groups:
1) straight - droplets of non-polar fluid in the polar medium (oil in water);
2) Reverse (water in oil).
Changing the composition of emulsions or external impact can lead to the transformation of direct emulsion in the opposite and vice versa. Examples of the most famous natural emulsions are milk (direct emulsion) and oil (reverse emulsion). A typical biological emulsion is a drop of fat in the lymph.
L and b about r and t about p. Pour whole milk to the plate. Drip to the surface of several multicolored droplets of food dyes. Mix with a cotton wand and tap the center of the plate. Milk begins to move, and the colors to mix. Why?
From those known in the practical activity of human emulsions can be called lubricating fluids, bitumen materials, pesticide preparations, medicinal and cosmetics, food products. For example, in medical practice, fat emulsions are widely used for the energy supply of a starving or weakened organism by intravenous infusion. To obtain such emulsions, olive, cotton and soybean oil are used.
In chemical technology, emulsion polymerization is widely used as the main method for producing rubbers, polystyrene, polyvinyl acetate, etc.
Suspension - these are coarse systems with a solid dispersed phase and a liquid dispersion medium.
Usually, the particles of the dispersed phase of the suspension are so large that they settle under the action of gravity - sediment. Systems in which sedimentation is very slow due to a small difference in the density of the dispersed phase and the dispersion medium are also called the suspenders. Practically significant construction suspensions
washes are whitewashes ("Lime Milk"), enamel paints, various construction suspensions, such as those called "cement mortar". Suspensions also include medical preparations, such as liquid ointments - lintences.
The special group consists of coarse systems, in which the concentration of the dispersed phase is relatively high compared with its small concentration in suspensions. Such dispersed systems are called pasta. For example, you are well known from everyday life dental, cosmetic, hygienic, etc.
Aerosols- These are coarse systems in which the dispersion medium is air, and the disperse phase can be droplets of a liquid (clouds, a rainbow, released from a spray cliner for hair or deodorant) or particles of a solid (dust cloud, tornado) (Fig. 16).

Fig. 16. Examples of coarse systems with solid

Dispersed phase: a - suspension - mortar;
b - aerosol - dust storm
Colloid systems. Colloid systems occupy an intermediate position between coarse systems and true solutions. They are widespread in nature. Soil, clay, natural waters, many minerals, including some precious stones, are all colloidal systems.
Colloidal systems for biology and medicine have great importance. The composition of any living organism includes solid, liquid and gaseous substances that are in a complex relationship with the environment. From a chemical point of view, the body as a whole is the most complicated set of many colloidal systems.
Biological fluids (blood, plasma, lymph, spinal fluid, etc.) are colloidal systems in which such organic compounds such as proteins, cholesterol, glycogen and many others are in colloidal state. Why exactly does nature give such preference? This feature is limited, first of all, so that the substance in the colloidal state has a large surface of the section between the phases, which contributes to the better flow of the metabolic reactions.
La b about r and t o r n s o p s t. In a plastic cup, pour the starch tablespoon. Gradually add warm water and thoroughly rub the mixture with a spoon. It is impossible to pour water, the mixture should be thick. Putting a tablespoon of the resulting colloidal solution to the palm and touch the finger of another hand. The mixture is hardening. If you remove your finger, the mixture becomes liquid again.
Pressure colloids can change their condition. As a result of the pressure of the finger on the cooked colloid, starch particles are connected to each other, and the mixture becomes solid. When the pressure is weakening, the mixture returns to the initial liquid state.

Colloid systems are divided into salty (colloidal Solutions) I. gels (jelly).
Most biological cell fluids (already mentioned cytoplasm, nuclear juice - karyoplasm, the contents of vacuoles) and the living organism as a whole are colloidal solutions (zolas).
For gold, the phenomenon of coagulation is characterized, i.e. The sticking of colloidal particles and their precipitate. In this case, the colloidal solution turns into a suspension or gel. Some organic colloids are coagulated when heated (egg protein, adhesives) or by changing the acid-base environment (digestive juices).
Gels- These are colloidal systems in which particles of the dispersed phase form a spatial structure.
Gels are dispersed systems that are found in everyday life (Scheme 2).
Scheme 2.
Classification of gel

Over time, the structure of the gels is broken - liquid is distinguished from them. Syneresis occurs - spontaneous decrease in the size of the gel, accompanied by a liquid separation. Syneresis determines the shelf life of food, medical and cosmetic gels. Biological syneresis is very important when cooking cheese, cottage cheese. In warm-blooded animals, there is a process that is called blood clotting: under the action of specific factors, the soluble blood protein fibrinogen turns into fibrin, whose clot, in the process of synerresis, is compacted and clogs the wound. If blood clotting is difficult, then they are talking about the possibility of human disease hemophilia. As you know from the course of biology, the carriers of the hemophilia gene are women, and they sick with her men. The historical dynastic example is well known: the Russian Romanovsky dynasty has suffered for this disease, reigning more than 300 years.
In appearance, true and colloidal solutions are difficult to distinguish each other. To do this, the tyndal effect is used - the formation of the "luminous track" cone when passing through the colloidal solution of the beam of light (Fig. 17). The particles of the dispersed phase of the sol reflect the light, and the particles of the true solution - no. A similar effect, but only for an aerosol, and not a liquid colloid, you can observe in the cinema when the beam is passed from the cinema preparation through the dyed air of the visual hall.

Fig. 17. The thyndal effect allows you to visually distinguish
True solution (in the right glass) from colloidal
(in the left glass)

? 1. What are dispersed systems? Dispersion environment? Dispersed phase?
2. How do you classize dispersed systems for the aggregate state of the environment and phase? Give examples.
3. Why air, natural gas and true solutions do not relate to dispersed systems?
4. How are the coarse systems divided? Name representatives of each group and specify their value.
5. How are finely dispersed systems subdivided? Name representatives of each group and specify their value.
6. What subgroups can gels separate? What determines the shelf life of cosmetic, medical and food gels?
7. What is coagulation? What can it be called?
8. What is synerresis? What can it be called?
9. Why did Nature choose the colloid systems as a carrier of evolution?
10. Prepare a message on the topic "Aesthetic, biological and cultural role of colloidal systems in a person's life" using the Internet resources.
11. What disperse systems are we talking about in a small poem of M.TSvetaeva?
Take the pearl - the tears will remain,
Take the crown - the leaves will remain
Autumn maple, take Purpur -
Blood remains.

Sections: Chemistry

Class: 11

After examining the lesson, you will learn:

what are dispersed systems?
what are the disperse systems?
what properties do dispersed systems have?
the value of dispersed systems.

Clean substances in nature are very rare. Crystals of pure substances - sugar or table salt, for example, you can get a different size - large and small. Whatever the size of crystals, they all have the same internal structure for a given substance - a molecular or ion crystal lattice.

In nature, mixtures of various substances are most often found. Mixtures of different substances in various aggregate states can form heterogeneous and homogeneous systems. Such systems we will call dispersed.

The disperse is called a system consisting of two or more substances, and one of them in the form of very small particles is evenly distributed in the volume of the other.

The substance falls into ions, molecules, atoms, which means "crushing" to the smallest particles. "Crushing"\u003e dispersion, i.e. Substances are dispersed to different sizes of particles visible and invisible.

The substance that is present in smaller quantities disperses and is distributed in the volume of the other, called dispersed phase. It can consist of several substances.

The substance present in greater quantities in the amount of which the dispersed phase is distributed, called dispersed medium. There is a section of the section between it and particles of the dispersed phase, so the dispersed systems are called heterogeneous (inhomogeneous).

And the dispersion medium, and the dispersed phase can be substances that are in various aggregate states - solid, liquid and gaseous.

Depending on the combination of the aggregate state of the disperse medium and the dispersed phase, 9 types of such systems can be distinguished.

Table
Examples of dispersed systems

Dispersion environment	Dispersed phase	Examples of some natural and domestic dispersed systems
Gas	Gas	Always homogeneous mixture (air, natural gas)
	Liquid	Fog, backway gas with oil droplets, carburetor mixture in car engines (gasoline droplets in the air), aerosols
	Solid	Dust in the air, smoke, smoke, samums (dust and sandy storms), aerosols
Liquid	Gas	Swiming drinks, foam
	Liquid	Emulsions. Liquid media organism (blood plasma, lymph, digestive juices), liquid content of cells (cytoplasm, karyoplasm)
	Solid	Zati, gels, pastes (Kisli, jelly, adhesives). River and sea righteous in water; Construction solutions
Solid	Gas	Snow-in-law with air bubbles in it, soil, textile fabrics, brick and ceramics, foam rubber, porous chocolate, powders
	Liquid	Wet soil, medical and cosmetics (ointment, mascara, lipstick, etc.)
	Solid	Mountain breeds, colored glasses, some alloys

The magnitude of the particles of substances constituting the dispersed phase, the dispersed systems are divided into coarse (suspension) with particle sizes more than 100 nm and finely dispersed (Colloidal solutions or colloidal systems) with particle sizes from 100 to 1 nm. If the substance is fragmented to molecules or ions of less than 1 nm, a homogeneous system is formed - solution. It is homogeneous, the surface of the partition between the particles and the medium is not.

Dispersed systems and solutions are very important in everyday life and in nature. Judge for yourself: without Nilsk, the Great Civilization of Ancient Egypt would not take place; Without water, air, rocks and minerals at all, there would be no living planet - our common house - Earth; No cells would not have live organisms, etc.

Suspend

Weighs are dispersed systems in which the particle size of the phase is more than 100 nm. These are opaque systems, separate particles of which can be noticed by the naked eye. The dispersed phase and the dispersed medium are easily separated by upholding, filtering. Such systems are divided into:

Emulsions (both medium and phase are insoluble in each other fluid). From water and oil you can prepare an emulsion with a long shaking of the mixture. These are well-known milk, lymph, water-level paints, etc.
Suspension(Wednesday - liquid, phase - soluble solid in it). To prepare a suspension, it is necessary to grind the substance to a thin powder, pour into the liquid and shake well. Over time, the particle will fall on the bottom of the vessel. Obviously, the smaller the particle, the longer the suspension will persist. These are building solutions that suspended in water river and sea silica, a lively suspension of microscopic living organisms in sea water - plankton, which feeds the giants - whales, etc.
Aerosols suspension in gas (for example, in air) small particles of liquids or solids. Dust, smoke, fogs differ. The first two types of aerosols are suspension of solid particles in gas (larger particles in dust), the latter - suspension of liquid droplets in gas. For example: fog, thunderstorm clouds - suspend in the air of water droplets, smoke - small solid particles. A was able to hang over the largest cities of the world, also an aerosol with a solid and liquid dispersed phase. Residents of settlements near cement factories suffer from the thinner of the subtlest cement dust, which is generated during the grinding of cement raw materials and the product of its firing - clinker. Smoke factory pipes, smsi, the smallest droplets of saliva, departing from the mouth of a patient with flu, also harmful aerolosis. Aerosols play an important role in nature, everyday life and human production activities. Clouds accumulation, field treatment of chemicals, applying paintwork coatings using a pulverizer, treatment of respiratory tract (inhalation) - examples of those phenomena and processes where aerosols benefit. The aerosols are fogs over the sea, near the waterfalls and fountains, the rainbow arising in them delivers a man joy, aesthetic pleasure.

For chemistry, dispersed systems are most important in which the medium is water and liquid solutions.

Natural water always contains dissolved substances. Natural aqueous solutions are involved in the process of soil formation and supply plant with nutrients. The complex processes of vital activity occurring in human and animal organisms also flow in solutions. Many technological processes in the chemical and other industries, such as the preparation of acids, metals, paper, soda, fertilizers, flow in solutions.

Colloid Systems

Colloidal systems (translated from the Greek "Call" - glue, "Eidos" kind of adhesive) – These are such dispersed systems in which the particle size of the phase from 100 to 1 nm. These particles are not visible to the naked eye, and the dispersed phase and the dispersed medium in such systems upholding are separated with difficulty.

From the course of general biology, you know that particles of this size can be found using an ultramicroscope, which uses the principle of light scattering. Thanks to this, the colloidal particle in it seems like a bright point on a dark background.

They are subdivided into evil (colloidal solutions) and gels (jelly).

1. Colloidal solutions, or evil. This is most of the liquids of the living cell (cytoplasm, nuclear juice - karyoplasm, the contents of organoids and vacuoles). And a living organism as a whole (blood, lymph, tissue fluid, digestive juices, etc.) Such systems form adhesives, starch, proteins, some polymers.

Colloidal solutions can be obtained as a result of chemical reactions; For example, when the solutions of potassium silicates or sodium ("soluble glass") with acid solutions, a colloid solution of silicic acid is formed. The sol formed in the hydrolysis of iron (III) chloride in hot water.

The characteristic property of colloidal solutions is their transparency. Colloidal solutions are externally similar to true solutions. They are distinguished from the last on the resulting "luminous path" - a cone when passing through them the beam of light. This phenomenon is called the tyndal effect. Large than in a true solution, particles of the dispersed phase of sol reflect the light from its surface, and the observer sees a glowing cone in a vessel with a colloidal solution. In a true solution, it is not formed. A similar effect, but only for aerosol, not a liquid colloid, you can observe in the forest and in cinemas when the ray of light from the cinema preparation through the air of the cinema hall.

Transmission of the beam of light through solutions;

a is a true solution of sodium chloride;
B - colloidal solution of iron hydroxide (III).

The particles of the dispersed phase of colloidal solutions are often not settled even with long-term storage due to continuous collisions with solvent molecules due to thermal motion. They do not stick together when converging with each other due to the presence of the same electrical charges on their surface. This is explained by the fact that substances in the colloidal, i.e., in small-cerebral, condition possesses a large surface. On this surface, either positively charged or negatively charged ions are adsorbed. For example, silicic acid adsorb negative SiO 3 ions, which in the solution a lot due to the dissociation of sodium silicate:

The particles with the same charges are mutually repelled and therefore do not stick together.

But under certain conditions, the coagulation process may occur. When boiling some colloidal solutions, the charged ions are desorbed, i.e. Colloid particles lose charge. Begin to enlighten and settle. The same is observed when touched any electrolyte. In this case, the colloidal particle attracts the oppositely charged ion to itself and its charge is neutralized.

Coagulation - the phenomenon of sticking of colloidal particles and their precipitate - is observed when neutralizing the charges of these particles, when electrolyte is added to the colloidal solution. In this case, the solution turns into a suspension or gel. Some organic colloids are coagulated when heated (glue, egg protein) or with a change in the acid-alkaline environment of the solution.

2. Geli or jelly are centered precipitates formed when coagulation of asses. These include a large number of polymeric gels, so well-known confectionery, cosmetic and medical gels (gelatin, keel, marmalade, bird milk cake) and of course endless many natural gels: minerals (opal), body jellyfish, cartilage, tendons , hair, muscle and nervous fabric, etc. The history of development on Earth can be simultaneously considered the history of the evolution of the colloidal state of the substance. Over time, the structure of the gels is broken (peeling) - water is distinguished from them. This phenomenon is called synerresis.

Perform laboratory experiments on the topic (group work, in the group of 4 people).

You are issued a sample of the dispersed system. Your task: determine which dispersed system is issued.

Students issued: a solution of sugar, iron (III) chloride solution, a mixture of water and river sand, gelatin, aluminum chloride solution, salt salt, a mixture of water and vegetable oil.

Laboratory Experience Instructions

Consider the sample carefully issued to you (external description). Fill in Count number 1 table.
Mix the disperse system. Watch for the ability to deposit.

It is deposited or placed within a few minutes or with difficulty for a long time, or not precipitated. Fill in Count number 2 tables.

If you do not observe the deposition of particles, explore it on the coagulation process. Place a little solution into two test tubes and add to one 2-3 drops of yellow blood salts and to another 3-5 drops of alkali, what are you watching?

Skip the disperse system through the filter. What are you watching? Fill in Count number 3 tables. (Filter a little bit in the test tube).
Skip the lantern light bullet through the solution on a dark paper background. What are you watching? (You can observe the effect of the tyonda)
Take a conclusion: What is this disperse system? What is the disperse medium? What is a dispersed phase? What are the dimensions of the particles in it? (Count number 5).

Sincweight("Sinwen" -from fr. Words meaning "five") is a poem of 5 lines according to a specific topic. For essay sincweune. 5 minutes is given, after which the written poems can be voiced and discussed in pairs, groups or on the entire audience.

Writing rules sincweune.:

In the first line in one word (usually noun) is called the topic.
The second line is a description of this topic with two adjectives.
The third line is three verbs (or verb shapes), calling the most characteristic actions of the subject.
The fourth line is a phrase of four words showing personal attitude to the topic.
The last line is synonymous with the topic, emphasizing its essence.

Summer 2008 Vienna. Shenbrunn.

Summer 2008 Nizhny Novgorod region.

Clouds and their role in human life

All nature around us - the organisms of animals and plants, the hydrosphere and the atmosphere, the earth bark and subsoil are a complex set of many diverse and variety of coarse and colloidal systems.
The development of colloid chemistry is associated with topical problems of various areas of natural science and technology.
The present image presents the clouds - one of the types of aerosols of colloidal dispersed systems. In the study of atmospheric precipitation, meteorology relies on the doctrine of aerodice systems.
The clouds of our planet are the same living entities as the whole nature that surrounds us. They are of great importance for the Earth, as they are information channels. After all, the clouds consist of a capillary substance of water, and water, as you know, a very good information drive. The cycle of water in nature leads to the fact that information on the state of the planet and the mood of people accumulates in the atmosphere, and together with the clouds moves throughout the space of the Earth.
The clouds are an amazing creature of nature, which delivers a man joy, aesthetic pleasure.

Krasnova Maria,
11th "b" class

R.S.
Thank you very much Pershina OG, Chemistry teacher MOU Gymnasium "Dmitrov", worked at the lesson with the presentation found, and it was complemented by our examples.

Clean substances in nature are very rare. Mixtures of different substances in various aggregate states can form heterogeneous and homogeneous systems - dispersed systems and solutions.

The substance that is present in smaller quantities and is distributed in the volume of the other, called the dispersed phase. It can consist of several substances.

A substance present in greater quantities in which the dispersed phase is distributed, called the dispersion medium. Between it and the particles of the dispersed phase there is a section of the section, so the dispersed systems are called heterogeneous (inhomogeneous).

Both the dispersion medium and the dispersed phase can be substances that are in various aggregate states - solid, liquid and gaseous.

Depending on the combination of the aggregate state of the dispersion medium and the dispersed phase, 8 species of such systems can be distinguished (Table 11).

Table 11.
Examples of dispersed systems

A quick acquaintance with dispersed systems and solutions shows how important they are in everyday life and in nature (see Table 11).

The classification of dispersed systems and solutions is presented in Scheme 2.

Scheme 2.
Classification of dispersed systems and solutions

Suspend

Weighs are dispersed systems in which the particle size of the phase is more than 100 nm. These are opaque systems, separate particles of which can be noticed by the naked eye. The dispersed phase and the dispersion medium are easily divided by upholding. Such systems are divided into three groups:

emulsions (and medium, and phase are insoluble in each other fluid). These are well-known milk, lymph, waterfront paints, etc.;
suspension (medium - liquid, and the phase is an insoluble solid in it). These are building solutions (for example, "lime milk" for blissing), weighted in water river and sea sil, lively suspension of microscopic living organisms in sea water - plankton, which feed the giants of whales, and so on;
aerosols - suspension in gas (for example, in air) small particles of liquids or solids. Distinguish dust, smoke, fog. The first two types of aerosols are suspension of solid particles in a gas (larger particles in dust), the latter - the suspension of small droplets of the liquid in the gas. For example, natural aerosols: fog, thunderstorm clouds - suspend in the air of water droplets, smoke - small solid particles. A was able to hang over the largest cities of the world, also an aerosol with a solid and liquid dispersed phase. Residents of settlements near cement factories suffer from the thinner of the subtlest cement dust, which is generated during the grinding of cement raw materials and the product of its firing - clinker. Similar harmful aerosols - dust - are also in cities with metallurgical production. Smoke factory pipes, smsi, the smallest droplets of saliva, departing from the mouth of the patient with the flu, also harmful aerosols.

Aerosols play an important role in nature, everyday life and human production activities. Clusters of clouds, field treatment of chemicals, applying paintwork coatings with a pulverizer, spraying of fuel, production of dry dairy products, treatment of respiratory tract (inhalation) - examples of those phenomena and processes where aerosols benefit.

The aerosols are fogs over the sea, near the waterfalls and fountains, the rainbow arising in them delivers a man joy, aesthetic pleasure.

For chemistry, dispersed systems are most important in which the medium is water.

Colloid Systems

Colloid systems are such dispersion systems in which the particle size of a phase from 100 to 1 nm. These particles are not visible to the naked eye, and the dispersed phase and the dispersion medium in such systems upholding are separated by difficulty.

They are divided into evil (colloidal solutions) and gels (jelly).

1. Colloid solutions, or salty. This is the majority of liquids of the living cell (cytoplasm, nuclear juice - karyoplasm, the contents of organoids and vacuoles) and the living organism as a whole (blood, lymph, tissue liquid, digestive juices, humoral fluids, etc.). Such systems form adhesives, starch, proteins, some polymers.

Colloidal solutions can be obtained as a result of chemical reactions; For example, when the solutions of potassium silicates or sodium ("soluble glass") with acid solutions are formed by a colloid solution of silicic acid. The sol formed in the hydrolysis of iron (III) chloride in hot water. Colloidal solutions are externally similar to true solutions. They are distinguished from the latter by the resulting "luminous path" - a cone when passing through them the beam of light. This phenomenon is called the tyndal effect. Large than in a true solution, particles of the dispersed phase of sol reflect the light from its surface, and the observer sees a glowing cone in a vessel with a colloidal solution. In a true solution, it is not formed. A similar effect, but only for an aerosol, not a liquid colloid, you can observe in cinemas when the ray of light from the film preparation through the air of the cinema hall.

Coagulation - The phenomenon of sticking of colloidal particles and precipitate them is observed when neutralizing the charges of these particles, when electrolyte is added to the colloidal solution. In this case, the solution turns into a suspension or gel. Some organic colloids are coagulated when heated (glue, egg protein) or with a change in the acid-alkaline environment of the solution.

2. The second subgroup of colloid systems is gels, or jelly In pupils, which are pupils formed during coagulation of asses. These include a large number of polymeric gels, so well-known confectionery, cosmetic and medical gels (gelatin, keel, jelly, marmalade, cake-souffle "Bird's milk") and of course the infinite many natural gels: Minerals (opal), Body Jellyfish , cartilage, tendons, hair, muscle and nervous fabric, etc. The history of the development of life on Earth can be simultaneously considered the history of the evolution of the colloidal state of the substance. Over time, the structure of the gels is broken - water is distinguished from them. This phenomenon is called synerresis.

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