What phenomenon results from the expansion of liquids and gases when heated?

The correct choice, which is convective currents, refers to the movement of fluid (liquid or gas) that occurs as a result of temperature differences within the fluid. When a fluid is heated, it expands and becomes less dense. As a consequence, the warmer, less dense fluid rises, while the cooler, denser fluid sinks. This process creates a cycle of movement—known as convection—which is vital in many natural and man-made systems, such as weather patterns, cooking, and heating systems.

In contrast, conduction involves the transfer of heat through direct contact between materials, not necessarily involving the movement of the fluid itself. Radiation is the transfer of heat through electromagnetic waves and does not require a medium. Evaporation specifically pertains to the phase transition from liquid to gas as molecules gain enough energy to escape the surface of a liquid, rather than the bulk movement of fluids caused by temperature changes. Understanding convective currents is crucial, as it helps explain how heat distributes in environments and affects various systems around us.