Someone at school was lucky at chemistry lessonsjust write boring control and calculate the molar mass or indicate the valence, 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 chemistry lessons, passing the next element fromperiodic table, as well as all the main substances, it was necessarily discussed 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, 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 - this is known to everyone. It simply does not dissolve, but it remains to float bubbles or a film on the surface, since its density is less. But why so and what else are hydrophobic substances?
Usually this group includes fats, someproteins 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 material with H2O looks like a film or droplets, or the liquid remains on the surface and takes the form of a ball, because it has the smallest surface area and provides minimal contact.
Hydrophobic properties are explained by the chemical structure of these or other 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 simpleguess, 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, in fact, all substances are hydrophilic to a greater or lesser degree.
Amphiphilic
And is it so that hydrophobic substances cansimultaneously have hydrophilic properties? 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, you can findthere 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 recent years, scientists are developing newhydrophobic substances, by means of which it is possible to protect various materials from wetting and soiling, thus creating even self-cleaning surfaces. Clothes, metal products, building materials, automotive glass - 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 the opportunity to reduce the degree of pollution of nature by cleaning agents. So further developments will benefit everyone.
