Definition of Chemical Mixture

Candela Rocío Barbisan | Oct. 2021
Chemical engineer

Unlike the phenomenon observed with pure substances, where when taking any portion the properties are preserved, in this case, we cannot assure it, Since each portion of matter in a mixture, for example sand and rice, does not have a specific composition and the properties can vary from sample to sample. other.

By means of physical separation methods we can obtain the different compounds of a mixture, without altering the composition of each one of them. That is, by knowing the physical properties of each of the substances that make up the sample, these can be used in order to achieve the desired separation. For example, properties such as density can be used to separate lentils and water. Other physical properties could be the solubility, the color or the temperature melting and boiling.

Differences and examples between homogeneous and heterogeneous mixtures

When two or more phases are observed in the mixture, it is easy to characterize it as a mixture and is called the heterogeneous type. For example, a mixture of sand and water is a heterogeneous mixture, since each of the components is in different “regions”.

Now, if we dissolve table salt (NaCl) in water, a solution and it is what is known as a homogeneous mixture. In this case, the composition will be constant and it is practically impossible to distinguish each of the substances that compose it. However, the physical properties of the pure substances differ from those of the mixture; for example, the melting point of water differs from the melting point of an aqueous sodium chloride solution.

Every day we are in contact with mixtures, for example, the gasoline we use in our car is a liquid mixture (solution) that does not contain water, this demystifies the idea that all solutions are made up of Water. Solutions are formed by a solute and a solvent, where the solvent is the substance that dissolves the solute and, in the particular case that it is water, the solution is called aqueous.

We find solutions in the different states of aggregation of matter, such is the case of solid solutions such as bronze, whose composition is 70-95% of Copper (Cu), 1-25% of Zinc (Zn) and 1-18% of Tin (Sn) used to make coating, for example. Most metals combine to form alloys that are widely used, such is the case of stainless steel used in the metal industry. food for the manufacturing of containers of storage, kitchen and bazaar instruments (such as pots and thermos) and in the petrochemical industry thanks to its difficulty to corrode. Finally, we have homogeneous gaseous mixtures and the most typical is the air made up of different gases as nitrogen and oxygen, to a lesser extent.

In short, mixtures are present at every step we take, from the moment we get up and drink a glass. of milk at breakfast to even in the soldering of the cables of the electrical connection of our home.

In the case of homogeneous mixtures, to separate them into the original pure substances that compose them, other physical properties such as boiling temperature can be used. For example, if you have a mixture of water and sugar, this solution can be heated to the point where all the water is evaporated and the sucrose remains in the container. Another case would be in which there are two solid compounds and the greater solubility of one of them is used in a certain solvent to be extracted from its solution. Undissolved compound can be easily removed by a filtration while, on the other side, we will have a solution, a homogeneous mixture between a solvent and a solute. If desired, another separation method may be used to separate solvent and solute.

Methods that are widely used in the industry are: distillation, crystallization, extraction with solvents, among others. On the other hand, methods such as sieving or decantation in the case of heterogeneous mixtures.