When roasting marshmallows over a campfire without touching the fire, what type of heat transfer cooks the marshmallows?

What the question is really asking

You are being asked to identify the heat transfer method that works even when two objects are not touching. The key clue is that the marshmallow is held away from the fire.

Matching the situation to the three heat-transfer types

• Conduction: heat transfer by direct contact. This would matter if the marshmallow touched the hot stick or coals.
• Convection: heat transfer by moving fluid (hot air rising). This can warm the marshmallow, especially if it is in the stream of hot air.
• Radiation: heat transfer by electromagnetic waves (mostly infrared) that can travel through air and across empty space.

Why radiation is the best answer here

Because the marshmallow cooks without touching the fire, the heat must be able to cross the air gap. The flames and coals emit strong infrared radiation, which is absorbed by the marshmallow’s surface, heating it and causing browning.

Quick check

If you feel heat on your face when you stand near a campfire, that is mostly radiation, the same process cooking the marshmallow.