Question

what is origin of viscosity in gases and liduids

Answer 1

Gases:-

On increasing the temperature, the kinetic energy of gas molecules increases and they collide more with each other. As a result, there is restricted flow of gas molecules. Hence, the viscosity of a gas increases with increase in temperature.

Liquids:-

On increasing the temperature, the cohesive forces between the liquid molecules reduce and the liquid tends to flow more easily. Hence, the viscosity of a liquid decreases with increase in temperature.