Mechanical Properties Of Fluid

Viscosity is defined as the resistance to the change in shape or movement of a fluid (liquid or gas). In simple words, viscosity is the opposition to the flow by a fluid. 

An increase is temperature has different effects on the viscosity of a liquid and a gas. 

• With increase in temperature, the cohesive forces present in the liquid decreases, thereby increasing the rate of molecular interchange. Thus, the viscosity of a liquid decreases with increase in temperature. 
• On the other hand, the molecules of gases are far apart from each other. An increase in temperature causes these molecules to move faster and collide with each other. This collision results in an increased resistance, thereby increasing the viscosity. 

Hence, with increase in temperature, the viscosity of gas increases while that of liquid decreases.