Viscosity and fludity

Defination:

    "Liquid's resistance to flow".

                      OR

    " The frictional effect between different layers of a flowing fluid ".

Explanation:

It is the property which opposes the relative motion of adjacent layers of liquid. 

The substances that cannot flow easily have large coefficient of viscosity. (such as honey)whereas the substances that can flow easily have small coefficient of viscosity (Such as water).

Factors:

It depends upon: 

•The strength of Intermolecular force 

•Structure of the compound

•Shape of the molecule

The force which is required to maintain the steady flow of liquid in direction of the force is directly proportional to the viscosity gradient which is normal to the direction of flow. 

Defination:

   "It is the force per unit area , needed to maintain unit difference of velocity between two parallel layers of the liquid , unit distance apart." 

Unit of viscosity "poise":

"When  a force of one dyne per square cm is maintained, between two layers which are 1cm apart and the difference of velocity between the two layers is 1cm per second, then it is called poise. "

           1poise =10^-1 kg m^-1 s^-1

            1 centipoise =10^-2 poise

            1 millipoise =10^-3 poise

Effect of temperature on viscosity:

   The viscosity of a liquid falls with the increase in temperature.

It is estimated that for each one degree rise of temperature, there is 2% decrease of viscosity.

Fluidity:

       " Fluidity is the reciprocal of viscosity".

The units of fluidity are reciprocal of viscosity.(poise^-1).