Before talking about the properties of water, it is worthdeal with the very concept of "water". It is a clear liquid, which in most cases does not have a characteristic color or smell. When water passes into another aggregate state, it forms derivatives, which are called ice, snow (solid states) or vapor (gaseous state). It is believed that it covers more than 70% of the surface of the planet Earth - it's all kinds of seas and oceans, rivers, lakes, glaciers and other hydrological objects.
Water is a strong solvent, which inNatural conditions contains a lot of mineral salts and various gases. If we talk about its physical properties, we immediately pay attention to the fact that when the ice melts, its density increases, while for other substances a similar process occurs to the exact opposite.
The main feature of water is viscosity. Viscosity itself is the ability of a substance (be it liquid, gas or solid) to resist while moving particles of matter relative to each other. This characteristic can be of two types - volumetric and tangential. Volumetric viscosity is the ability of a substance to accept a tensile force. It manifests itself in the propagation in the water of sound or ultrasonic waves. Tangential viscosity is characterized by the ability of the fluid to withstand shearing force.
When scientists examined the viscosity of water, it wasIt was found that the resistance of the substance under stretching and shear depends on the velocity of the particles of different layers of the liquid. If a layer that moves faster affects a layer that moves slower, then an accelerating force is applied. If everything happens the other way around, then the braking force begins to act. The above forces are directed tangentially to the surfaces of the layers.
According to Newton's law, the formula τ = μdv / dn, according to which the internal friction force is proportional to the velocity gradient in the normal and area of the impact. If we refer the force of friction to an area that is equal to unity, we obtain a tangential stress in the liquid, which is indicated in the above formula.
There is also such a thing askinematic viscosity of water. It denotes the ratio of the dynamic coefficient (μ) to the density of the selected fluid (ρ). As a formula, this expression will look like this: ν = μ / ρ.
Viscosity of water at different temperatureschanges, that is, the values of its coefficients decrease with increasing temperature. Thus, the dynamic coefficient of viscosity of salt water will differ slightly from the freshwater coefficient. When calculating the indicator, the difference will fluctuate around 5%.
We can give some more formulas, but this is neitherwhich, as the main material was described earlier. The viscosity of water, by definition, can vary, not to mention the aggregate states of matter. These data are important in aircraft and shipbuilding and some other industries.
There is a special table for determiningviscosity of water under different temperature conditions. This material can be used not only in theory, but also in practice. In the table data are given with an interval of 5 degrees, ranging from 5 to 100 degrees, which greatly facilitates the life of teachers and students of universities when performing calculations.
Another important indicator is dynamickinematic viscosity of water, the so-called second viscosity (bulk) - is a characteristic of volume compression deformation. It plays a significant role in the attenuation of sound and in the reduction of shock waves.
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