Boiling water is what type of heat transfer?

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

Answer: (B)

The main idea is convection. When water is heated from below, the water at the bottom becomes hotter and less dense, so it rises. Cooler, denser water moves down to take its place and get heated, creating circulating currents that transfer heat through the liquid. Radiation would involve energy transfer by waves from the heat source, not the movement of the liquid itself, and evaporation is a phase change that happens as a result of heat input, not the method by which heat travels through the water. Conduction plays a role at the boundary where heat first enters the water, but within the bulk of the boiling liquid, convection is the dominant transfer mechanism.