Abnormal density of ice and water

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 vary with temperature and pressure. And ice has these unique properties. It is worth saying that the definition of density can be carried out using the formula ρ = m / V. Accordingly, this criterion can be established through the study of the mass of matter of the medium per unit volume.

Let's look at some properties of ice and water. For example, the density anomaly. After melting, the density of ice increases, passing through a critical mark of 4 degrees, and only after this begins to decrease with increasing temperature. However, in ordinary liquids, it always decreases during cooling. This fact finds a completely scientific explanation. The higher the temperature, the higher the molecular velocity. This leads to their repulsion by each other, and, accordingly, the substance becomes more friable. The riddle of water also consists in the fact that, despite the increase in the velocity of molecules with increasing temperature, The decrease in its density occurs only at high temperatures.

The second mystery is the question: "Why can ice float on the surface of the water?", "Why does not it freeze to the bottom in the 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 is less than that of a crystal. This is due to the fact that in the latter the molecules have a certain periodicity and are located regularly. This is typical for crystals of any substances. However, in addition, they have the molecules "packed" fairly tightly. During the melting of the crystal, the regularity disappears, which is possible only with a less dense bond of the molecules. Accordingly, the density of matter decreases during melting. But this criterion changes quite a bit, for example, when smelting metals, it drops by an average of only 3 percent. However, the density of ice is less than the density of water at once by ten percent. Therefore, we can say that this jump is anomalous not only with its sign, but also with its magnitude.

The data of the puzzle is explained by the features of the ice structure. It is a grid of hydrogen bonds, where in each node there are four. Therefore, the grid is called a quad. All angles in it are equal to qT, therefore it is called tetrahedral. Moreover, it consists of six-membered rings of curved shape.

A feature of the structure of solid water is that the packed molecules are loose in it. If they were in close relationship, the ice density would be 2.0 g / cm3, and in reality it is 0.92 g / cm3. This led to the conclusion that the presence of large spatial volumes should lead to the appearance of instability. In fact, the grid does not become less sturdy, but it can be rebuilt. Ice is such a strong material that the ancestors of the modern Eskimos learned to build their huts from it. And to this day, residents of the Arctic use ice as a building material. Accordingly, with increasing pressure, the ice structure changes. It is in this stability that the main property of the hydrogen bonds of the meshes between H ₂ O molecules is composed. Accordingly, each water molecule and in the liquid state retains four hydrogen bonds, but the angles become different from qT, which leads to the fact that the density of ice is less, Than water.