Define viscosity and coefficient of viscosity. How does the viscosity of liquids varies with temperature.

Explanation

IT is well known that all liquids do not flow with the same speed. Some liquids like water, alcohol, ether etc. Flow very rapidly while someone like glycerine,honey,castor oil etc. flow slowly. This indicates that every liquid has some internal resistance to flow. THis internal resistance to flow possessed by a liquid is called its viscosity.
Liquids which flow rapidly have low internal resistance . So their viscosity is less, Liquids which flow slowly have high internal resistance. So their viscosity is high.
Coefficient of viscosity is the force per unit area required to maintain unit difference of velocity between two parallel layers in the liquid, one unit apart.
Units: Dyne `cm^-2` (C.G.S) or Poise Millipoise =`10^-3` Poise
Ns`m^-2` or Pa s (pascal second) is S.I Unit.
Examples :
1) Glass is not a solid. It is a super -cooled liquid with a very high viscosity.
2) `H_2SO_4` is viscous, due to H-bonding.
Viscosity of liquids decreases as the temperature rises because at high temperature molecules have high kinetic energy and can overcome the intermolecular forces to slip past one another between layers.