Questions: Thermal Energy Transfer: Conduction, Convection, and Radiation

Question 1

How does the Sun's heat reach Earth?

• A. Conduction through space
• B. Convection through space
• C. Radiation through space
• D. All three equally

Answer: (C)

Space is a vacuum with no matter for conduction or convection. The Sun's energy reaches Earth as electromagnetic radiation, which does not need a medium.

Question 2

When you stir hot soup with a metal spoon, heat reaches your hand through conduction.

• T. True
• F. False

Answer: True

Heat transfers through the metal spoon by conduction — vibrating particles in the hot end pass energy to neighboring particles, working up the spoon to your hand.

Question 3

Why does warm air rise above a heater?

Model answer: When air is heated, it expands and becomes less dense than the cooler air above it. The lighter warm air rises while denser cool air sinks, creating a convection current.

Convection occurs because heating a fluid decreases its density. The buoyant, less-dense warm air rises, and cooler, denser air flows in to replace it, forming a circulation pattern.