Which statement about convection is accurate?

Which statement about convection is accurate?

• A. They transfer energy by direct contact only.
• B. Hotter, less dense regions rise while cooler, denser regions sink.
• C. They occur only in gases.
• D. They move in a straight line.

Answer: (B)

Convection is a heat-transfer process in fluids driven by buoyancy from temperature-induced density differences. When part of a fluid is heated, it becomes less dense and rises, while cooler, denser parts sink, creating a circulating flow. This is exactly what the statement describes: hotter, less dense regions rise and cooler, denser regions sink, producing a vertical and looping motion that transports heat. This mechanism works in liquids and gases, not just air or any single phase, and it explains phenomena from cooking pots to atmospheric and oceanic circulation. It’s different from conduction, which transfers energy through direct contact without bulk movement, and from any notion of straight-line motion—convection currents bend into vertical and circular patterns as the fluid moves to equalize temperature.

Convection is a heat-transfer process in fluids driven by buoyancy from temperature-induced density differences. When part of a fluid is heated, it becomes less dense and rises, while cooler, denser parts sink, creating a circulating flow. This is exactly what the statement describes: hotter, less dense regions rise and cooler, denser regions sink, producing a vertical and looping motion that transports heat.

This mechanism works in liquids and gases, not just air or any single phase, and it explains phenomena from cooking pots to atmospheric and oceanic circulation. It’s different from conduction, which transfers energy through direct contact without bulk movement, and from any notion of straight-line motion—convection currents bend into vertical and circular patterns as the fluid moves to equalize temperature.