Someone at school was lucky in chemistry classes not only to write boring tests and calculate the molar mass or indicate valency, but also to look at how the teacher conducts the experiments. Invariably, as part of an experiment, as if by magic, liquids in test tubes changed color unpredictably, and something else could explode or burn out beautifully. Perhaps not so spectacular, but still interesting experiments that use hydrophilic and hydrophobic substances. By the way, what is it and what are they curious about?
Physical properties
In chemistry classes, passing the next element from the periodic table, as well as all the main substances, they were necessarily talking about their various characteristics. In particular, their physical properties were affected: density, state of aggregation under normal conditions, melting and boiling points, hardness, color, electrical conductivity, thermal conductivity, and many others. Sometimes it was a question of such characteristics as hydrophobicity or hydrophilicity, but separately, as a rule, they do not talk about this. Meanwhile, this is a rather interesting group of substances that can easily be encountered in everyday life. So it will be useful to learn more about them.
Hydrophobic substances
Examples can easily be taken from life. So, you can not mix water with oil - this is known to everyone. It simply does not dissolve, but remains to float with bubbles or film on the surface, since its density is less. But why and what other hydrophobic substances exist?
Usually this group includes fats, some proteins and nucleic acids, as well as silicones. The name of the substance comes from the Greek words hydor - water and phobos - fear, but this does not mean that the molecules are afraid. They are simply slightly or completely insoluble, they are also called non-polar. Absolute hydrophobicity does not happen, 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 H 2 O 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 it happens, for example, with hydrocarbons.
Hydrophilic substances
The name of this group, as is already easy to 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 the "polar", includes simple alcohols, sugars, amino acids, etc. Accordingly, they have such characteristics because they have high energy of attraction to the water molecule. Strictly speaking, in fact, all substances are hydrophilic to a greater or lesser extent.
Amphiphilic
But 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 both soluble - polar and water-repellent - non-polar elements in its structure. Such properties, for example, are possessed by certain 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, the polar groups turn out to be fluid-oriented.
Meaning and Application in Life
In addition to the interaction of water and oil, one can find a lot of evidence that hydrophobic substances are found almost everywhere. So, the clean surfaces of metals, semiconductors, as well as animal skin, plant leaves, insect chitinous cover have similar properties.
In nature, both types of substances are important. So, hydrophiles are used in the transport of
nutrients in animals and plants, and the final metabolic products are also excreted using solutions of biological fluids. Non-polar substances are of great importance in the formation of cell membranes having
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 hydrophobic substances, with which you can protect various materials from wetting and contamination, thus creating even self-cleaning surfaces. Clothing, metal products, building materials, car glass - there are many areas of application. Further study of this topic will lead to the development of multifobic substances, which will become the basis for dirt-repellent surfaces. By creating such materials, people will be able to save time, money and resources, and it will also be possible to reduce the degree of environmental pollution with cleaning products. So further development will benefit everyone.