Three different mechanisms convey heat — conduction, radiation, and convection — and in many instances, all three may operate together.

Conduction is the transmission of heat through a material by contact between particles of matter without their displacement.

Metals are excellent heat conductors relative to most other materials. Air and other gases are poor conductors because heat transfer can only take place by movement of their molecules, which are much further apart than those of metals or solid objects.

The amount of heat that flows through any substance by conduction depends on the time, area, temperature differential, and the type of material. Because trapped still air is a poor conductor, it acts as an insulator, which is why fibrous and cellular insulation materials are efficient insulators. Free air, however, conducts heat by convection.

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