What occurs when warming a fluid?

When a fluid is warmed, the molecules within that fluid gain energy and begin to move more rapidly. This increase in molecular motion leads to a reduction in the density of the fluid. Density is defined as mass per unit volume, and as the temperature of the fluid increases, the volume expands while the overall mass remains relatively constant. Consequently, the density decreases because the warmer, less dense fluid will rise compared to the cooler, denser fluid.

This principle is fundamental in understanding convection processes, where warm fluid rises and cooler, denser fluid sinks, leading to the circulation patterns that distribute heat within a fluid. Therefore, option C accurately describes the behavior of a fluid when it is heated.