Question

isaac wants to make smores. he holds a marshmallow on a metal skewer over a fire. a few seconds later, the marshmallow is cooked and the skewer feels warm. what most likely happened?
the fire heated the surrounding air, which cooked the marshmallow.
the heat generated from the marshmallow flowed in the form of thermal energy to the skewer and fire.
the heat from the skewer cooked the marshmallow.
thermal energy in the form of heat moved from the fire to the skewer and marshmallow.

Explanation:

Heat transfer occurs from a hotter object to a cooler one. In this case, the fire is the source of thermal energy. Thermal energy (heat) moves from the fire (hotter) to the cooler metal skewer and marshmallow.

• Option 1: While air can transfer heat (convection), the main transfer here is likely conduction through the skewer (metal is a good conductor). But let's check all options.
• Option 2: The marshmallow doesn't generate heat to cook itself. It is heated by an external source (the fire).
• Option 3: Heat flows from hotter to cooler. The fire is hotter than the skewer and marshmallow initially. So heat doesn't flow from marshmallow (which is being cooked, so not yet a heat - generating source) to fire.
• Option 4: Thermal energy (heat) moves from the fire (high - temperature source) to the skewer (metal, conductor) and marshmallow (which gets cooked as it absorbs heat).

Answer:

Thermal energy in the form of heat moved from the fire to the skewer and marshmallow.