Question

With rise in temperature, viscosity of a liquid?
A. Increases
B. Decreases
C. Remains constant
D. May increase or decrease.

Answer 1

Hint: Viscosity of a liquid is defined as a measure of a fluid’s resistance of a flow or in simpler words if the fluid is resisting towards flow its viscosity is more and if the fluid is easily flowing then it is less viscous.

Complete step by step answer:
Now, as we know about the viscosity for a liquid, Let’s know about how the factor stated make changes in the viscosity of liquid:
Viscosity basically depends on the intermolecular forces of attraction; more is the intermolecular forces higher is the viscosity and vice versa. Now the effect of temperature has an inverse relation with the viscosity as when there is an increase in the temperature the average kinetic energy of molecules has a tendency to increase this results in faster moving molecules and a decrease in the intermolecular forces and a decrease in the viscosity of a liquid.
Hence, the correct answer is Option B.

Note:
However, rather than the inverse relation of temperature with the viscosity of liquids the temperature has a direct relation with the viscosity of gases as with the rise in temperature the viscosity of the gas molecules increases, and there is one more factor on which the viscosity of a liquid depends and that is shape of the molecule if the molecule has branched structures they are more viscous and this causes a resistivity in flow and causes an increase in the viscosity, and the molecules which have no branching have low resistivity of flow and thus a decrease in the viscosity.