Question

what causes the air above a pot of boiling water to become warm?
the air transfers thermal energy to the water vapor.
the water vapor transfers thermal energy to the air.
the particles in the air lose kinetic energy.
the particles in the water vapor gain kinetic energy.

Explanation:

When water boils, it turns into water vapor (steam). The water vapor is hot. Thermal energy is transferred from the hot water vapor (which has high - energy particles) to the surrounding air. This transfer of thermal energy makes the air warm.

• Option 1: The air does not transfer thermal energy to the water vapor. The water vapor is already hot (from the boiling water), so this option is incorrect.
• Option 2: Since the water vapor is hot (has more thermal energy), it transfers thermal energy to the air, which is a correct description of the process.
• Option 3: If the particles in the air lost kinetic energy, the air would cool down, not warm up. So this option is incorrect.
• Option 4: The particles in the water vapor already have high kinetic energy (because the water is boiling). The key is the transfer of energy from water vapor to air, not just the gain of kinetic energy in water - vapor particles for heating the air. So this option is not the best explanation for the air warming.

Answer:

The water vapor transfers thermal energy to the air.