MIXTURE: COMPONENTS, TYPES, SEPARATION METHODS, EXAMPLES - CULTURE VOCABULARY - 2025

A mixture is the combination of two or more materials, substances, or compounds. As far as chemistry and physics are concerned, it is assumed that the components of said mixture should not react with each other, since their composition and properties would change as time passes; therefore, they must be stable for a reasonable time (hours, days, weeks, years).

Mixtures are everywhere and in all areas of knowledge; some are ideological, others chimerical or natural. We can find them in the kitchen, not only in foods that are in themselves solid and heterogeneous mixtures, but in the same materials, the wooden table, glasses, jugs with juices, and other edible or not objects.

A cup of chocolate meringue, like all desserts, are daily examples of mixes. Source: Pxhere.

Mixtures are also found in toothpaste, mouthwash, shaving cream, soap bars, cleaning products, or eau de toilette scents; even our physiological waste is it in its proper measure. The human body is made of a set of different types of mixtures, coordinated in balance.

It is possible to increase the complexity of a mix as much as our imagination allows us; the number of components, the phases involved, their interactions with the surroundings. That is why for a first approach to this concept, we always start from the typical mixtures found in a laboratory or in daily, past or modern life.

Water is the ideal medium to explain what a mixture is, as it is capable of dissolving many solids or liquids. Using it, it is described what a solvent, a solute, the size of the particles, the homogeneity or heterogeneity of the resulting solution consists of. And then, going further, it becomes clear that any liquid, solid or gas, can act as a solvent.

Components of a mixture

Although there are hundreds of thousands of mixtures, their components can be reduced and classified into just two types: solvent or solute.

Solvent

At first, an example of a solvent was given: water. In fact, it's called a universal solvent (or solvent) for good reason. It can then be thought that a solvent must necessarily be liquid, so that it dissolves the solids or gases that interact with it; however, such a statement is incorrect.

The solvent is the medium capable of “receiving” the solids, substances, compounds or materials that are added to it; and therefore, it tends to have the highest composition (to be more abundant) in the mixture. For example, the amounts of dissolved salts in the oceans are overwhelmingly large, but they pale in comparison to their total mass of water.

If the solvent is a medium, it means that it does not always have to be liquid; it can also be a solid or even a gas. Likewise, a solvent does not have to be of a single material (only water), but can be treated by itself in a mixture (water and alcohol in equal proportions).

Among other common solvents we can name: glacial acetic acid, salts or molten metals, toluene, chloroform, gasoline, nitrogen, air, mesoporous bodies, among others.

Solute

The solute is simply what is added or dissolved in said solvent (substances, compounds, etc.). Its physical state can be any, although the solid is the most representative and observable in nature. Furthermore, it is characterized by being in a lower proportion (it is less abundant) with respect to the solvent; although it doesn't always have to be that way. In the following example, water is the solvent and salt is the solute:

Mix types

Suppose A is the solvent, and B is the solute. If A and B are mixed or combined, they will result in a mixture (A + B). Said mixture can be classified regarding its material state (liquid, gas or solid), according to its appearance (homogeneous or heterogeneous), or according to the size of the solute particles (suspension, colloid or solution).

All these classifications are related to each other, but mixtures will be addressed based on their appearances while also referring to their particle size.

Homogeneous

Glass of water, homogeneous mixture

A homogeneous mixture is one that presents a single phase to the naked eye, and that cannot be separated by itself due to the effect of gravity. Therefore, its particles are too small for the human eye to appreciate.

Solutions and colloids enter into this type of mixture, differentiated in the size of the solute particles. All solutions are homogeneous.

Heterogeneous

Heterogeneous mixture of oil and water

A heterogeneous mixture is one that presents more than two phases to the naked eye, as well as a non-uniform distribution of its particles observed on a molecular scale. Therefore, it can be a mixture of solids of different colors, or of gases or immiscible liquids. Colloids, especially emulsions, and suspensions, enter into this type of mixture.

There are therefore homogeneous colloids, like clouds, and heterogeneous, like mayonnaise seen under a microscope and water with emulsified oil. However, all colloids are heterogeneous when viewed under the microscope or micrometer scales.

Mixture separation methods

The components (solvent and solute) of the mixture A + B can be separated depending on what type of mixture it is and the material state of it.

Evaporation

Water evaporating from kitchen utensil. Vidralta, from Wikimedia Commons

Evaporation is used for solutions, applying heat so that the solvent escapes into the gas phase and the solute remains settled on the walls of the container. This is observed in a bucket of seawater: once the water evaporates, the white salts will remain at the bottom.

Distillation

Distillation is used if you do not want to discard the solvent but rather recover it. However, the main use of distillation is to separate a solution made up of a mixture of liquids; that is, where the solute is also liquid. For example, a water-acetone mixture is distilled to recover the lower-boiling acetone.

Filtration

Filtration requires filter paper or a porous surface that allows liquid to pass through, but whose pores are small enough to retain the solid.

Filtration is especially useful for separating suspensions, where it takes time for solid particles to settle to the bottom. In chemistry, it is the step after a precipitation reaction.

Decantation

Separating funnel

When it is a liquid-solid mixture, wait for the solid to settle at the bottom (according to its density and particle size), pour the liquid into another container, taking care that the solid does not move in the background.

Meanwhile, in liquid-liquid mixtures (heterogeneous), the famous separating funnel (similar to a pear or backstage) is used. The densest liquid is transferred through the narrow nozzle at the bottom, and the less dense, through the wide mouth at the top (where the cap goes).

Sifting

Sieving is a filtration but for solid-solid (heterogeneous) mixtures. Thanks to this method, grains or stones of different sizes are separated by using a sieve or sieve.

Sublimation

When one of the components of the solid-solid mixture is volatile, that is, it passes to the gaseous state without melting or melting first, then it is heated and its purified crystals are deposited on a cold surface, leaving behind the mixture without the sublimable component.

Crystallization

A solid-solid mixture is dissolved in an appropriate solvent so that, depending on the solubilities of each solute in the solvent, they can be separated by the action of temperature and cooling. Thus, as the hot mixture cools, each solute will crystallize separately, which allows its crystals to filter.

Centrifugation

In centrifugation, the colloids by action of gravity and acceleration end up with their components (dispersed phase and dispersant phase for colloids) separated. It is used when filtration is not possible as the particles are too small and penetrate the porous medium as well as the solvent or dispersing phase.

Examples of mixtures

-Amalgams (solid solution)

-Cement (homogeneous solid mixture)

-Toothpaste (colloid but homogeneous to the naked eye)

-Gaseous drinks (solutions)

- Sand (heterogeneous mix)

-Cereals with milk (heterogeneous mix)

- Rice chicha with chocolate chips (heterogeneous mixture with suspended chips)

-Blood (colloid but homogeneous to the naked eye)

-Gelatin (solid-liquid colloid)

-Plastics (solid solution)

-Beers (solutions)

-Orine (solution)

-Air (gaseous solution)

-Dust in air (suspension)

-Milk (colloid and emulsion)

-Colorful glass (solid solution)

-Mud (suspension)

-Chalk in water (suspension)

-Black coffee (solution)

-Bones (heterogeneous mixture)

-Paints (colloids or suspensions depending on the type)

-Clouds and mist (gaseous colloids homogeneous to the naked eye)

-Pickles and caesar salad (smorgasbord)

-Granite (heterogeneous mix)

-Tizanas (heterogeneous mixture)

-Vinegar (homogeneous mixture or solution)

-Gasoline (homogeneous mixture)

-Heavy oil tanker (suspension)

-Acid rain (solution)

-Aceros (solid solution)

-Milk chocolate (homogeneous mixture)

-Nutella (homogeneous mixture although it is surely colloidal)

-Box of chocolates (mixed bag)

-Melted caramel (homogeneous mixture)

-Ink (colloid but homogeneous in sight)

-Deodorants in bars (homogeneous mixture)

-Powder detergents (heterogeneous mixture)

References

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5. Ron Kurtus. (September 15, 2005). Types of Mixtures. Recovered from: school-for-champions.com
6. Amrita.olabs.edu.in,. (2012). Separation of Mixtures Using Different Techniques. Recovered from: amrita.olabs.edu.in
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