There are no elements in nature that are pure. Basically, they are all mixtures. They, in turn, can be heterogeneous or homogeneous. They are formed from substances in the state of aggregation, thus creating a certain dispersion system in which there are various phases. In addition, mixtures usually contain a dispersion medium. Its essence lies in the fact that it is considered an element with a large volume in which some substance is distributed. In a dispersed system, the phase and the medium are located in such a way that there are particles of the interface between them. Therefore, it is called heterogeneous or heterogeneous. In view of this, the action of the surface, and not of the particles as a whole, is of great importance.
Disperse system classification
Phase, as you know, is represented by substances that have a different state. And these elements are divided into several types. The state of aggregation of the dispersed phase depends on the combination ofenvironment, resulting in 9 types of systems:
- Gas. Liquid, solid and the element in question. Homogeneous mixture, mist, dust, aerosols.
- Liquid dispersed phase. Gas, solid, water. Foams, emulsions, sols.
- Solid dispersed phase. Liquid, gas and the substance considered in this case. Soil, means in medicine or cosmetics, rocks.
As a rule, the size of a dispersed system is determined by the size of the phase particles. There is the following classification:
- coarse (suspensions);
- thin (colloidal and true solutions).
Particles of the dispersion system
When examining coarse mixtures, one can observe that the particles of these compounds in the structure can be seen with the naked eye, due to the fact that their size is more than 100 nm. Suspensions, as a rule, refer to a system in which the dispersed phase is separable from the medium. This is because they are considered opaque. Suspensions are divided into emulsions (insoluble liquids), aerosols (fine particles and solids), suspensions (solid in water).
A colloidal substance is anything that has the quality of having another element evenly dispersed over it. That is, it is present, or rather, it is part of the dispersed phase. This is a state when one material is completely distributed in another, or rather in its volume. In the milk example, liquid fat is dispersed in an aqueous solution. In this case, the smaller molecule is within 1nanometer and 1 micrometer, making it invisible to an optical microscope when the mixture becomes homogeneous.
That is, no part of the solution has a greater or lesser concentration of the dispersed phase than any other. We can say that it is colloidal in nature. The larger one is called the continuous 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, foams, dispersions, and mixtures called hydrosols. Each such system has two phases: a dispersed and a continuous phase.
Colloids by history
Intense 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 the time, this new field of science was the leading research area for theorists, researchers and manufacturers. After the peak of interest until 1950, research on colloids declined significantly. It is interesting to note that since the recent emergence of higher power microscopes and "nanotechnologies" (the study of objects of a certain tiny scale), scientific interest in the study of new materials has again increased.
More about these substances
There are elements observed both in nature and in artificial solutions that have colloidal properties. For example, mayonnaise, cosmetic lotion, and lubricants are types of artificial emulsions, and milk is a similara mixture found in nature. Colloidal foams include whipped cream and shaving foam, while edible items include butter, marshmallows, and jelly. In addition to food, these substances exist in the form of certain alloys, paints, inks, detergents, insecticides, aerosols, styrofoam, and rubber. Even beautiful natural objects like clouds, pearls and opals have colloidal properties because they have another substance evenly distributed through them.
Obtaining colloidal mixtures
By increasing small molecules to the range of 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 regular liquids. And this is observed in transport and physico-chemical properties. For example, a membrane may allow a true solution with solid molecules attached to liquid molecules to pass through it. Whereas a colloidal substance which has a solid dispersed through a liquid will be stretched by the membrane. The parity of the distribution is uniform up to the point of microscopic equality in the gap over the entire second element.
True solutions
Colloid dispersion is represented as a homogeneous mixture. The element consists of two systems: continuous and dispersed phase. This indicates that this case is related totrue solutions, because they are directly related to the above mixture, consisting of several substances. In a colloid, the second has the structure of tiny particles or drops, which are evenly distributed in the first. From 1 nm to 100 nm is the size constituting the dispersed phase, or rather the particles, in at least one dimension. In this range, the dispersed phase is homogeneous mixtures with the indicated sizes, we can name approximate elements that fit the description: colloidal aerosols, emulsions, foams, hydrosols. Substantially affected by the chemical composition of the surface are the particles or droplets present in the compositions in question.
Colloid solutions and systems
One should take into account the fact that the size of the dispersed phase is a hard-to-measure variable in the system. Solutions are sometimes characterized by their own properties. To make it easier to perceive the indicators of the compositions, colloids resemble them and look almost the same. For example, if it has a liquid-dispersed, solid form. As a result, particles will not pass through the membrane. While other components like dissolved ions or molecules are able to pass through it. If it is simpler to analyze, it turns out that the dissolved components pass through the membrane, and with the phase in question, colloidal particles cannot.
The appearance and disappearance of color characteristics
Due to the Tyndall effect, some of these substances are translucent. In the structure of the element, it is the scattering of light. Other systems and formulations come withsome shade or even be opaque, with a certain color, even if some are even dim. Many familiar substances, including butter, milk, cream, aerosols (fog, smog, smoke), asph alt, paints, paints, glue, and sea foam, are colloids. This field of study was introduced in 1861 by the Scottish scientist Thomas Graham. In some cases, a colloid can be considered as a homogeneous (not heterogeneous) mixture. This is because the distinction between "dissolved" and "granular" matter can sometimes be a matter of approach.
Hydrocolloid types of substances
This component is defined as a colloidal system in which particles are dispersed in water. Hydrocolloid elements, depending on the amount of liquid, can take on various states, for example, a gel or a sol. They are irreversible (single-component) or reversible. For example, agar, the second type of hydrocolloid. Can exist in gel and sol states, and alternate between states with heat added or removed.
Many hydrocolloids are derived from natural sources. For example, carrageenan is extracted from algae, gelatin is from bovine fat, and pectin is from citrus peel and apple pomace. Hydrocolloids are used in food mainly to affect texture or viscosity (sauce). Also used for skin care or as a healing agent after injury.
Essential characteristics of colloidal systems
From this information it can be seen that colloidal systems are a subsection of the dispersed sphere. They, in turn, can be solutions (sols)or gels (jelly). The former are in most cases created on the basis of living chemistry. The latter are formed under the sediments that occur during the coagulation of the sols. Solutions can be aqueous with organic substances, with weak or strong electrolytes. The particle sizes of the dispersed phase of colloids are from 100 to 1 nm. They cannot be seen with the naked eye. As a result of settling, the phase and medium are difficult to separate.
Classification by types of particles of the dispersed phase
Multimolecular colloids. When, in dissolution, atoms or smaller molecules of substances (having a diameter of less than 1 nm) combine together to form particles of similar sizes. In these sols, 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. In these colloids, particles are held together by van der Waals forces. They usually have a lyophilic character. This means significant particle interaction.
High molecular weight colloids. These are substances that have large molecules (so-called macromolecules), which, when dissolved, form a certain diameter. Such substances are called macromolecular colloids. These dispersed phase forming elements are typically polymers having very high molecular weights. Natural macromolecules are starch, cellulose, proteins, enzymes, gelatin, etc. Artificial ones include synthetic polymers such as nylon, polyethylene, plastics, polystyrene, etc.e. They are usually lyophobic, which means in this case the weak interaction of the particles.
Associated colloids. These are substances that, when dissolved in a medium, behave like normal electrolytes at low concentration. But they are colloidal particles with a larger enzymatic component of the components due to the formation of aggregated elements. The aggregate particles thus formed are called micelles. Their molecules contain both lyophilic and lyophobic groups.
Micelles. They are clustered or aggregated particles formed by the association of a colloid in solution. Common examples are soaps and detergents. The formation occurs above a certain Kraft temperature, and above a certain critical micellization concentration. They are able to form ions. Micelles can contain up to 100 molecules or more, for example sodium stearate is a typical example. When it dissolves in water, it releases ions.
