Question

For liquids, the viscosity decreases as the temperature increases. For gases, the viscosity increases as the temperature increases. Your objective is to provide an explanation for these trends. You may do internet research, but your response must be in your own words and references provided. Your response must be typed and grammatically correct.

Answer 1

In gases, the viscosity increases with increase in temperature. For gases, the viscosity is proportional to the square root of absolute temperature. And, thus when the temperature increases, the viscosity increases.

For liquid, the viscosity decreases with increase in temperature. In liquids, there will be molecular interchange similar to gases but there is an additional attractive, cohesive forces between the molecules of liquids. Hence, cohesive force and molecular interchange both act as a factor in liquid for viscosity. The increase in temperature results in decreases in cohesive forces between the molecules of liquid which furthur results in increasing the rate of molecular interchange. Hence, the net effect comes out as, with increase in temperature of liquid, there will be decrease in viscosity.