How does an increase in temperature affect the viscosity of a fluid?

An increase in temperature generally leads to a decrease in the viscosity of a fluid. Viscosity is a measure of a fluid's resistance to flow; as temperature rises, the energy of the fluid's molecules increases. This heightened molecular activity allows the molecules to move more freely and reduces the intermolecular forces that cause resistance to flow. Consequently, the fluid becomes less viscous and flows more easily at elevated temperatures.

This phenomenon is particularly evident in liquids, where heating them often makes them easier to pour and manipulate, showcasing the direct relationship between temperature and viscosity. Understanding this relationship is fundamental in refrigeration and fluid dynamics, as it affects the efficiency and performance of refrigeration systems where the flow of refrigerants is critical.

In contrast, some options relate to different concepts—like the notion of viscosity being constant or varying simply with pressure— which do not accurately capture how temperature impacts viscosity in fluids.