Which term describes the transfer of heat by the movement of a substance or mass?

The term that describes the transfer of heat by the movement of a substance or mass is convection. This process occurs in fluids—liquids and gases—where warmer, less dense areas of the fluid rise and cooler, denser areas sink, creating a continuous circulation pattern. This movement transports heat energy throughout the fluid, leading to an overall transfer of thermal energy.

In contrast, conduction refers to the transfer of heat through direct contact between materials without the movement of the material itself, which is why it is not the correct answer. Radiation involves the transfer of heat through electromagnetic waves and does not require a medium, making it a totally different mechanism of heat transfer. Diffusion relates to the spreading out of particles from an area of high concentration to one of lower concentration and is not primarily a heat transfer mechanism. Thus, convection accurately represents the concept of heat transfer through the movement of a substance.