Which describes convection?

• A. The movement of heat energy through the motion of matter such as steam or hot air
• B. The transfer of heat energy by direct contact
• C. The transfer of energy with electromagnetic waves
• D. The conversion of electricity to heat

Answer: (A)

Convection is heat transfer through the bulk movement of a fluid. When a portion of the fluid is heated, it becomes less dense and rises, while cooler, denser fluid sinks to take its place, creating a circulating current that moves heat with the fluid itself. That idea—heat energy moving by the motion of matter such as steam or hot air—fits convection perfectly.

In contrast, conduction is heat transfer by direct contact through a substance as particles collide and pass energy along, and radiation is heat transfer through electromagnetic waves that do not require a medium. The remaining option describes electricity turning into heat, which is about heat generation rather than transfer.