How does temperature influence the viscosity of a fluid?

The relationship between temperature and the viscosity of a fluid is primarily characterized by the behavior of the fluid molecules. When the temperature of a fluid increases, the kinetic energy of its molecules also increases. This increased energy causes the molecules to move more rapidly and freely, which reduces the internal friction or resistance to flow that is characteristic of viscosity.

In essence, viscosity is a measure of a fluid's resistance to deformation and flow. As temperature rises, the increased molecular motion allows the fluid to flow more easily, thereby decreasing its viscosity. This is particularly evident in liquids, where a rise in temperature can significantly lower the resistance to flow, making the liquid less viscous.

In contrast, at lower temperatures, the molecular motion is reduced, leading to a higher internal friction and thus a more viscous fluid. This fundamental principle applies to many common fluids, such as oils and water, making it clear that increased temperature generally results in decreased viscosity.