As you know, the substance in the liquid state retains its volume, but takes the shape of the vessel, it. Find out, how does this explain the molecular-kinetic theory.

The preservation of volume at a liquid proves, that between its molecules forces of attraction. Therefore, the distance between the molecules of the liquid must be smaller than the radius of molecular action. So, if molecules of a liquid describe the nature of molecular action, inside this sphere will be the centers of many other molecules, will interact with our molecule.

These forces hold the molecule of a liquid near its temporary equilibrium position within approximately 10^-12-10^-10 with, then it jumps to a new temporary equilibrium position by approximately the distance of its diameter. Liquid molecules between the switch perform an oscillatory motion about a temporary equilibrium position. The time between two molecules switch from one position to another is called time settled life. This time depends on the type of fluid and temperature. When heating a liquid average time of a settled life of molecules decreases.

During the time of settled life (order 10^-11 with) the majority of liquid molecules are held in their equilibrium positions, and only a small portion of their time to move on to a new position of balance. For a longer time most of the molecules of the liquid will have time to change your location. Therefore, the fluid is capable of flowing and taking the shape of the vessel, in which it is located.

Because the molecules of the liquid are very close to each other, it, having a sufficiently large kinetic energy, although they can overcome the attraction of its nearest neighbors, and out of their scope, it will fall into the scope of other molecules and will be in a new temporary state of equilibrium. Only on the free surface of the liquid molecules can escape outside the liquid, which explains the process of evaporation.

So, if in the liquid to provide a very small amount, in the course of time a settled life in him there is an ordered arrangement of molecules, similar to their location in the crystal lattice of a solid body. Then it falls apart, but occurs elsewhere. Thus, all the space, occupied by the liquid, like consists of a plurality of the crystal nuclei, which, however, unstable, t. e. break up in some places, but again there are other.

So, in a small volume of fluid is observed the ordered arrangement of its molecules, but in large volume it appears chaotic. In this sense, talking, what in liquids there is short-range order in the arrangement of molecules and there is no long-range order. Such a structure of a liquid is called quasicrystalline (crystal-like). Note, during a fairly intense heat, the time of settled life becomes very small and short-range order in the liquid almost disappears.

The liquid can detect mechanical properties, inherent in the solid body. If the duration of the force on the liquid a little, the fluid exhibits elastic properties. For example, with a sharp blow with a stick on the surface of the water, the stick may fly out or break; the stone can be thrown so, he when they hit the surface of the water bounces off it, and only having made a few jumps, sinks in water. If the exposure time of the liquid is large, instead of elasticity manifested fluidity fluid. For example, hand easily penetrates water.

At short-term action of force on a jet of fluid past encounters fragility. The strength of a liquid on break though and less, than solids, but little inferior to them in magnitude. For water, it is 2,5*10⁷ PA. Compressibility the liquid is also very small, although it is more, than these same substances in the solid state. For example, if you increase the pressure on 1 ATM the volume of water decreases on 50 ppm.

Breaks inside the liquid, in which no foreign matter, for example, air, can only be created when an intense impact on the liquid, for example, during rotation of the propeller in the water, during propagation in a liquid ultrasonic wave. This kind of emptiness inside liquid not survive for long and can sharply slam, t. e. disappear. This phenomenon is called cavitation (from the Greek "Civitas" — cavity). It is the cause of rapid wear of the propellers.

So, the liquids have many properties, General properties of solids. However, the higher the temperature of the liquid, the more its properties approach the properties of dense gases and stronger differ from the properties of solid bodies. This means, that the liquid state is intermediate between solid and gaseous States of matter.

It, when the transition of a substance from solid to liquid occurs less abrupt change in properties, than in the transition from a liquid to a gaseous. This means, what, generally speaking, properties of liquid state of matter closer to the properties of solid state, than to the properties of the gaseous.