Which of the following is NOT a factor of heat transfer?

The correct answer is that density of material is not a primary factor of heat transfer. In heat transfer, the main influencing factors include the temperature difference between two substances, thermal conductivity, and surface area.

Temperature difference drives the flow of heat between objects; the greater the temperature difference, the faster the heat transfer occurs. Thermal conductivity is a material property that indicates how well a substance conducts heat—higher values correspond to materials that transfer heat efficiently. Surface area plays a significant role as well; a larger surface area allows more heat to be exchanged between the surfaces involved in the heat transfer process.

While density may influence the physical characteristics of a material and its overall heat capacity or specific heat, it does not directly dictate the process by which heat is transferred. It is the combination of temperature difference, thermal conductivity, and surface area that primarily governs the heat transfer rate in various contexts.