What are hydrophobic substances?

Someone in the school was lucky at chemistry lessons not only to write boring control and calculate the molar mass or indicate valency, but also look at how the teacher conducts experiments. Invariably, as part of the experiment, as if by magic, the liquid in the test tubes changed color unpredictably, and something else could explode or burn nicely. Perhaps not so effective, but still interesting experiments in which hydrophilic and hydrophobic substances are used. By the way, what is this and what are they curious about?

Physical properties

At the chemistry lessons, passing the next element from the periodic table, as well as all the basic substances, it was necessary to talk about their various characteristics. Including their physical properties: density, aggregate state under normal conditions, melting and boiling point, hardness, color, electrical conductivity, thermal conductivity and many others. Sometimes there was talk about such characteristics as hydrophobicity or hydrophilicity, but separately, as a rule, they do not talk about it. Meanwhile, this is a fairly interesting group of substances that can be easily encountered in everyday life. So it is not out of place to learn more about them.

Hydrophobic substances

Examples can easily be taken from life. So, you can not mix water and oil - everyone knows this. It simply does not dissolve, but remains floating with bubbles or a film on the surface, since its density is smaller. But why so and what else are hydrophobic substances?

Usually, this group includes fats, some proteins and nucleic acids, as well as silicones. The name of the substances comes from the Greek words hydor - water and phobos - fear, but this does not mean that the molecules are afraid. Simply they are little or completely insoluble, they are also called non-polar. Absolute hydrophobicity does not happen, even those substances that seemingly do not interact with water at all still adsorb it, albeit in insignificant quantities. In practice, however, the contact of such a material with H ₂ O looks like a film or droplets, or the liquid remains on the surface and takes the form of a sphere, since it has the smallest surface area and provides minimal contact.

Hydrophobic properties are explained by the chemical structure of various substances. This is due to the low index of attraction to the water molecule, as happens, for example, with hydrocarbons.

Hydrophilic substances

The name of this group, as it is already easy to guess, also comes from the Greek words. But in this case the second part of philia is love, and it perfectly characterizes the relationship of such substances with water - complete "mutual understanding" and perfect solubility. This group, sometimes called "polar", includes simple alcohols, sugars, amino acids, etc. Accordingly, they have such characteristics, since they have a high energy of attraction to the water molecule. Strictly speaking, generally all substances are hydrophilic to a greater or lesser extent.

Amphiphilic

Does it happen that hydrophobic substances can have both hydrophilic properties at the same time? It turns out, yes! This group of substances is called diphilic, or amphiphilic. It turns out that the same molecule can have in its structure both soluble - polar and water-repellent - non-polar elements. Such properties, for example, have some proteins, lipids, surfactants, polymers and peptides. When interacting with water, they form various supermolecular structures: monolayers, liposomes, micelles, bilayer membranes, vesicles, etc. The polar groups are then oriented to the liquid.

Value and application in life

In addition to the interaction of water and oil, there are many confirmations that hydrophobic substances are encountered almost everywhere. Thus, the pure surfaces of metals, semiconductors, as well as the skin of animals, plant leaves, the chitinous cover of insects, have similar properties.

In nature, both types of substances are important. Thus, hydrophiles are used in the transport of nutrients in the organisms of animals and plants, the final products of metabolism are also derived by means of solutions of biological fluids. Nonpolar substances are of great importance in the formation of cell membranes that have selective permeability. That is why such properties play an important role in the course of biological processes.

In recent years, scientists have been developing all new hydrophobic substances, with which it is possible to protect various materials from wetting and contamination, thus creating even self-cleaning surfaces. Clothes, metal products, building materials, automotive glasses - a lot of applications. Further study of this topic will lead to the development of multi-phobic substances, which will become the main for dirt-repellent surfaces. By creating such materials, people will be able to save time, resources and resources, as well as there will be an opportunity to reduce the degree of pollution of nature by cleaning agents. So further developments will benefit everyone.