Someone at school was lucky in chemistry class not only to write boring tests and calculate molar mass or indicate valence, but also to watch how the teacher conducts experiments. Invariably, as part of the experiment, as if by magic, the liquids in the test tubes changed color unpredictably, and something else could explode or burn beautifully. Perhaps not so spectacular, but still interesting experiments in which hydrophilic and hydrophobic substances are used. By the way, what are they and why are they curious?
Physical properties
In chemistry lessons, going through the next element from the periodic table, as well as all the basic substances, we necessarily talked about their various characteristics. In particular, their physical properties were touched upon: density, state of aggregation under normal conditions, melting and boiling points, hardness, color, electrical conductivity, thermal conductivity, and many others. Sometimes there was talk about such characteristics as hydrophobicity or hydrophilicity, however, as a rule, they do not talk about this separately. Meanwhile, this is a rather interesting group of substances that can be easily encountered in everyday life. So it's not out of placewill learn more about them.
Hydrophobic substances
Examples can easily be taken from life. So, you can not mix water with oil - everyone knows this. It simply does not dissolve, but remains floating as bubbles or a film on the surface, since its density is less. But why is this and what other hydrophobic substances exist?
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. It's just that they are little or completely insoluble, they are also called non-polar. Absolute hydrophobicity does not exist, even those substances that, it would seem, do not interact with water at all, still adsorb it, albeit in negligible amounts. In practice, the contact of such a material with H2O looks like a film or droplets, or the liquid remains on the surface and takes the form of a ball, since it has the smallest surface area and provides minimal contact.
Hydrophobic properties are explained by the chemical structure of certain substances. This is due to the low attraction to the water molecule, as happens, for example, with hydrocarbons.
Hydrophilic substances
The name of this group, as you might guess, also comes from Greek words. But in this case, the second part of philia is love, and this perfectly characterizes the relationship of such substances with water -complete "mutual understanding" and excellent 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 extent.
Amphiphilicity
Does it happen that hydrophobic substances can simultaneously 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 supramolecular structures: monolayers, liposomes, micelles, bilayer membranes, vesicles, etc. In this case, polar groups turn out to be oriented towards the liquid.
Meaning and application in life
In addition to the interaction of water and oil, there is a lot of evidence that hydrophobic substances are found almost everywhere. So, clean surfaces of metals, semiconductors, as well as animal skin, plant leaves, insect chitin cover have similar properties.
In nature, both kinds of substances are important. Thus, hydrophiles are used in the transport of nutrients in animals and plants, end productsexchange are also excreted using solutions of biological fluids. Non-polar substances are of great importance in the formation of cell membranes with selective permeability. That is why such properties play an important role in the course of biological processes.
In recent years, scientists have been developing more and more new hydrophobic substances, with which it is possible to protect various materials from wetting and contamination, thus creating even self-cleaning surfaces. Clothing, metal products, building materials, automotive glass - there are many areas of application. Further study of this topic will lead to the development of multiphobic substances that will become the basis for dirt-repellent surfaces. By creating such materials, people can save time, money and resources, and it will also be possible to reduce the degree of pollution of nature with cleaning products. So further developments will benefit everyone.
