What is the fluid motion between regions of unequal heating called?

The term for fluid motion that occurs between regions of unequal heating is convection. This phenomenon is characterized by the movement of fluid (which can be either liquid or gas) due to temperature differences within the fluid itself. When a region of the fluid is heated, it becomes less dense and rises, while the cooler, denser regions sink. This creates a circulation pattern that transfers heat throughout the fluid.

Convection is a crucial mechanism in many natural and engineered systems, such as atmospheric weather patterns, ocean currents, and heating systems. It is distinct from conduction, which involves heat transfer through direct contact of materials, and radiation, which involves heat transfer through electromagnetic waves. Diffusion is a different process that describes the movement of particles from an area of higher concentration to an area of lower concentration, focusing on the mixing of substances rather than the movement of heat.