What is viscosity of liquid

What is viscosity of liquid

The viscosity is scientific the term which designates resistance to a current of liquid. Such resistance arises owing to the friction made by substance molecules and influences how strongly liquid will counteract the movement of an object through it. The viscosity depends on a number of factors, including on the size and a form of molecules, interaction between them and temperature.

Ways of measurement of viscosity

The viscosity of liquid can be measured in several ways by means of the devices called viscometers. Such devices measure time spent by substance for the movement or time necessary for an object with given size and density to pass through liquid. Units of measure for this parameter is Pascal in a square.

The factors affecting viscosity

As a rule, the liquids consisting of big molecules will have higher viscosity. It is especially well shown on the example of long chained substances which are polymers or heavier hydrocarbon connections. Such molecules, as a rule, block the friend from the friend, obstructing the traffic through them. Other important factor is how molecules interact with each other. Polar connections can form hydrogen communications which hold separate molecules together, increasing the general resistance to a stream or the movement. Though the water molecule also is polar, it has low viscosity because its molecules are rather small. The most viscous liquids, as a rule, those which have the stretched molecules or strong polarity. Glycerin and propylene glycol can be examples. Temperature has a great influence on viscosity. Measurements of properties of liquids are always given depending on temperature. In liquids the viscosity decreases with growth of temperature. It is possible to see it when heating syrup or honey. So occurs because molecules move quicker and, therefore, less time contact with each other. The viscosity of gases, on the contrary, increases with growth of temperature. It occurs because molecules move quicker and there are more collisions between them. Thus stream density increases.

Importance for the industry

Crude oil often moves to long distances between regions with a different temperature. Therefore the flow rate and pressure changes eventually. Oil which flows through Siberia is more viscous, than oil in pipelines of the Persian Gulf. Due to the differences in temperature of the external environment pressure in pipes to force it to flow have to be different also. For the solution of this problem in pipes at first special oil which possesses almost zero coefficient of internal resistance is filled in. The contact of oil with an internal surface of pipes is in such a way limited. The viscosity of oil also changes at temperature drop. To improve its characteristics add polymers which interfere with its solidification and mixing with oil to oil.

Author: «MirrorInfo» Dream Team