Which method of heat transfer involves circulation within a medium, such as a gas or liquid?

The method of heat transfer that involves circulation within a medium such as a gas or liquid is convection. This process occurs when warmer areas of a fluid rise while cooler areas sink, creating a circulation pattern. For example, when heating a pot of water on a stove, the water at the bottom becomes heated and rises to the surface, while cooler water descends to replace it. This movement facilitates the transfer of heat throughout the fluid.

Convection is particularly important in various applications, such as in heating and cooling systems, as it enables efficient heat distribution. It contrasts with conduction, which occurs through direct contact between molecules, and radiation, which involves transfer through electromagnetic waves without the need for a medium. Transmission refers more to the passage of energy through a material rather than the movement and circulation inherent in convection, further emphasizing why convection is the correct answer in this context.