Conduction is defined as which of the following?

• A. The circulation of heat from a warmer area to a cooler area; boiling, baking...
• B. The direct transfer of heat from one substance to another substance that it is touching.
• C. The use of steam to cook foods.
• D. The transfer of heat by radiation from hot surfaces.

Answer: (B)

Conduction is heat transfer through direct contact between substances. When two objects touch, the hotter one transfers energy to the cooler one by particle collisions and, in metals, by free electrons moving energy quickly from the hot region to the cooler region. The statement describing “direct transfer of heat from one substance to another that it is touching” captures this idea precisely.

This is different from convection, which involves heat moving through a fluid by the movement of the fluid itself, and from radiation, which transfers heat through electromagnetic waves without any contact. The steaming method and cooking with steam involve heat transfer by steam, not conduction, and boiling or baking are cooking processes rather than the specific mechanism of heat transfer.

For a simple example, placing a metal spoon in a hot pot transfers heat from the pot to the spoon by direct contact, warming the spoon along its length.