# Viscosity

## Viscosity

Do you know! “What is viscosity“. To understand about viscosity, we take example of some liquids like Honey and Water. As we know honey is thicker than water. So honey flow with very slow speed on floor than water, as water is very less thick so it flows quickly. Hence we can say that liquids with high thickness (like honey) flow slowly and have high viscosity while a liquid with low thickness (like water) flows quickly and have low viscosity.

### Definition of Viscosity

Viscosity can be defined as the fluids resistance to flow.

## What is Viscosity

Viscosity of a fluid is the measure of its resistance to gradual deformation by the tensile stress or shear stress. We can also say that viscosity is the internal resistance of the fluid. Fluids which have high viscosity resists to move as its molecular makeup gives this fluid a too much internal friction to motion, while fluids which have low viscosity resists less to move as its molecular makeup gives this fluid a less internal friction to motion so we can say that molecular makeup decides internal friction between them and which ultimately provides viscosity of fluid. Honey has high internal friction than water so honey have high viscosity than water.

Along with liquids or fluids, gases also have viscosity but it is very difficult to notice viscosity of gases at ordinary conditions.

To understand viscosity chemistry notes by Chemistry Notes Info ChemistryNotesInfo.com in simple way, we can say that, “Viscosity is the resistance of a fluid to change in its shape”,  viscosity is resistance to flow. Fluidity is the reciprocal of viscosity, So now we can say that honey has high viscosity and low fluidity while water has low viscosity and high fluidity.

Viscosity play very important role in determining characteristics of fluids used in lubrication and transportation, spraying, surface coating, injection molding etc.

### Formula of Viscosity

Viscosity = Force×Time ∕Area

#### Unit of Viscosity

Unit of Viscosity is Newton second per Square meter (Ns/m2)

SI unit of viscosity is Pascal second (Pas)

#### Relation of viscosity with temperature

Viscosity of the liquids decreases quickly with increase in the temperature, while viscosity of the gases increases with increase in the temperature.

 Temperature -> 27 °C 77 °C Viscosity of Water 0.85×10-3 pascal second 0.36×10-3 pascal second Viscosity of Air 1.85×10-5 pascal second 2.08×10-5 pascal second

### Measurement of viscosity

Viscosity is measured by various types of Rheometers or Viscometers.