Which method of heat transfer occurs in fluids by movement of heated particles?

• A. Conduction
• B. Radiation
• C. Convection
• D. Evaporation

Answer: (C)

Convection is heat transfer through a fluid by the movement of the fluid itself. When part of the fluid is heated, it becomes less dense and rises, while cooler, denser fluid sinks to take its place. This creates a circulating current that carries heat through the liquid or gas. You can see this in boiling water, air circulating from a heater, or ocean currents.

Conduction, by contrast, transfers energy through direct contact without bulk movement of the fluid, and radiation transfers heat through waves and can occur without a medium. Evaporation is a phase change at a surface, not the main way heat moves through a moving fluid.