Viscosity: Meaning and Top 4 Factors

In this article we will discuss about the Meaning and Factors of Viscosity.

Definition of Viscosity:

The resistance experienced by one layer of a liquid in moving over another layer is called “vis­cosity”. Viscosity varies greatly. Ether and gasoline have little viscosity and are quite mobile. But honey and coal-tar have high viscosities. The unit of viscosity is the “Poise”, named after Poiseuille.

It is expressed as:

Factors Affecting Viscosity:

1. Temperature:

The viscosity of liquids de­creases by about 2% for each degree rise in temperature.

2. Chemical Composition:

The viscosity of liquids generally depends upon the size, shape and chemical nature of their mol­ecules.

It is greater with larger than with smaller molecules; with elongated than with spherical molecules.

Large amounts of dissolved solids generally increase vis­cosity. Small amounts of electrolytes lower the viscosity of water slightly.

3. Colloid Systems:

The viscosity of lyophilic colloid solution is generally relatively high.

4. Suspended Material:

Suspended particles cause an increase in the viscosity. The vis­cosity of blood is important in relation to the resistance offered to the heart in circu­lating the blood. The heart muscle func­tions best while working against a certain resistance. The viscosity of blood is due largely to the emulsoid colloid system present in plasma and to the great propor­tion of suspended corpuscles.