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:
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.