The Macroscopic View
The resistance of a liquid to flow is called its viscosity. Viscous liquids like syrup and shampoo flow slowly. Less viscous liquids like water and gasoline flow quickly. The viscosity of a liquid usually depends on its temperature. Viscosity generally decreases as the temperature increases. Viscosity generally increases as the temperature decreases.
The Microscopic View
The viscosity of a liquid is related to the ease with which the molecules can move with respect to one another. Thus the viscosity of a liquid depends on the:
An Example of the Effect of Composition
Compare the structures of ethyl alcohol and ethylene glycol and explain why ethylene glycol has the higher viscosity.
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ethyl alcohol A low viscosity liquid at 25oC. |
ethylene glycol A high viscosity liquid at 25oC. |
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your answer.
An Example of the Effect of Structure
Compare the structure and composition of n-pentane and octadecane and explain why octadecane has the higher viscosity.
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n-pentane A low viscosity liquid at 25oC. |
octadecane A high viscosity liquid at 25oC. |
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your answer.
Explain why an increase in temperature generally results in a decrease in viscosity.
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