Which term describes the flow of particles in a liquid or gas that carries thermal energy?

The flow of particles in a liquid or gas that carries thermal energy is described by the term convection. This process involves the movement of fluid (which can be either a liquid or gas) caused by differences in temperature, leading to density variations. When a portion of a fluid is heated, it becomes less dense and rises, while cooler, denser fluid sinks to take its place. This continuous cycle creates a convection current, effectively transferring thermal energy throughout the fluid.

For instance, in a pot of boiling water, hot water rises to the surface, while cooler water descends to the bottom, thereby distributing heat throughout the liquid. Convection is a primary mode of heat transfer in many situations, particularly in fluids, making it distinct from conduction, which involves direct contact transfer of heat, and radiation, which transfers energy through electromagnetic waves without the need for a medium. Insulation, on the other hand, refers to materials or methods used to reduce heat transfer.