Water is a mysterious liquid. This is due to the fact that most of its properties are anomalous, i.e. different from other liquids. The reason lies in its special structure, which is due to hydrogen bonds between molecules that change with temperature and pressure. Ice also has these unique properties. It is worth saying that the density can be determined using the formula ρ=m/V. Accordingly, this criterion can be established through the study of the mass of the substance of the medium per unit volume.
Let's look at some properties of ice and water. For example, density anomaly. After melting, the density of ice increases, passing through a critical mark of 4 degrees, and only after that it begins to decrease with increasing temperature. However, in ordinary liquids, it always decreases in the process of cooling. This fact finds a completely scientific explanation. The higher the temperature, the faster the molecules. This leads to pushing them apart, and, accordingly, the substance becomes looser. The riddle of water also lies in the fact that, despite the increasespeed of molecules with increasing temperature,
its density decreases only at high temperatures.
The second riddle lies in the questions: "Why can ice float on the surface of the water?", "Why does it not freeze to the bottom in rivers?" The fact is that the density of ice is lower than that of water. And in the process of melting any other liquid, its density turns out to be less than that of a crystal. This is due to the fact that in the latter the molecules have a certain periodicity and are arranged regularly. This is typical for crystals of any substances. However, besides this, their molecules are “packed” rather densely. In the process of crystal melting, regularity disappears, which is possible only with a less dense bond of molecules. Accordingly, the density of the substance decreases in the process of melting. But this criterion changes quite a bit, for example, when melting metals, it decreases by an average of only 3 percent.
However, the density of ice is ten percent less than the density of water. Therefore, we can say that this jump is anomalous not only in its sign, but also in its magnitude.
These puzzles are explained by the peculiarities of the ice structure. It is a grid of hydrogen bonds, where there are four of them at each node. Therefore, the grid is called quadruple. All angles in it are equal to qT, so it is called tetrahedral. Moreover, it consists of six-membered rings of a curved shape.
A feature of the structure of solid water is thatpacked molecules loosely in it. If they were in close relationship, then the density of ice would be 2.0 g/cm3, while in reality it is 0.92 g/cm3. From this the conclusion should have followed that the presence of large spatial volumes should lead to the appearance of instability. In fact, the grid does not become less strong, but it can be rebuilt. Ice is such a strong material that even the ancestors of modern Eskimos learned to build their huts from it. To this day, the inhabitants of the Arctic use ice concrete as a building material. Accordingly, with increasing pressure, the structure of ice changes. It is precisely this stability that constitutes the main property of the hydrogen bonds of networks between H2O molecules. Accordingly, each water molecule retains four hydrogen bonds in the liquid state, but at the same time the angles become different from qT, which leads to the fact that the density of ice is less than that of water.
