Question

When temperature is increased, then which of the following is true?
a) Viscosity of the gas increases.
b) Viscosity of the gas decreases.
c) Viscosity of the liquid decreases.
d) Viscosity of the liquid increases.

• A. a and c are true
• B. b and c are true
• C. b and d are true
• D. a and d are true

Answer 1

Answer: (A)

a and c are true

As the temperature increases, the molecules carry more momentum and collide more often, that means more viscosity for gas.
As the temperature increases, the time of interaction between neighboring molecules of a liquid decreases because of the increased velocities of individual molecules. The macroscopic effect is that the inter molecular force appears to decrease and so does the bulk (or shear) viscosity.
So, as temperature increases, viscosity of gas increases and of liquid decreases.