What type of heat transfer occurs within a gas or liquid?

Convection is the type of heat transfer that occurs within a gas or liquid. It involves the movement of molecules within these fluids, whereby warmer, less dense areas rise and cooler, denser areas sink. This creates a circulation pattern that facilitates the transfer of heat throughout the fluid.

In practical terms, when you heat a pot of water on a stove, the water at the bottom gets hot first, rises to the top, while cooler water descends to take its place, effectively distributing heat throughout the entire body of water. This movement is characteristic of convection, which is crucial in many heating and cooling processes in both natural and engineered systems, such as in weather patterns and HVAC systems.

Other heat transfer methods, like conduction and radiation, operate differently. Conduction occurs through direct contact between solid materials, while radiation involves the transfer of energy through electromagnetic waves, which can occur in a vacuum and does not require a medium like a gas or liquid. Evaporation is a process related to phase change and cooling rather than heat transfer within fluids.