Question

Viscosity decreases with increase in temperature is the reason for
(i) Hot water moves faster than Cold water.
(ii) More viscous oils are used in motor cars during summer than in winter.
A. Only (i) is correct
B. Only (ii) correct
C. Both (i) and (ii) are correct
D. Both are wrong

Answer 1

Hint: With an expansion in temperature, there is continuously an increase in the sub-atomic exchange as particles move quicker in high temperatures. However in the liquid there are extra considerable attractive cohesive forces between the molecules of a liquid.

Complete answer:
The viscosity of gas can continuously increase with rising temperature. Both gas and liquid show very similar molecular interchange nature.
The aftereffect of expanding the temperature of a liquid is decline in viscosity since liquids have a lot higher intermolecular activity and attraction forces that keep the molecules quite closer together (i.e., that is the reason they are liquids).

Warming a liquid builds the energy level of the molecules to where those between intermolecular forces are debilitated and in this way; the resistance from movement through the liquid (i.e., the liquid viscosity) diminishes.

The effect will be to hinder the sphere in gases and to quicken it in liquids. In the event that we think about a liquid at room temperature, the molecules are firmly bound together by solid intermolecular forces or can say Van der Waal forces.

These appealing bound forces are liable for the viscosity since it is hard for each and every molecule to move from one place to another as they are firmly bound.

So, the correct answer is “Option C”.

Note:
The rise in temperature makes the reason for the increasing rate of kinetic energy and thus molecules become more mobile. The force of binding energy is reduced with the increasing value of kinetic energy and subsequently, the viscosity is reduced.
As the value of temperature increases, viscosity diminishes in liquids and increases in gases, and the drag force will do likewise.