What does heat flow depend on?

Heat flow fundamentally depends on the temperature difference between two regions. This principle is rooted in the second law of thermodynamics, which states that heat will naturally flow from a region of higher temperature to a region of lower temperature until thermal equilibrium is reached. The greater the temperature difference, the more rapid the heat transfer will occur. This relationship can be illustrated through Fourier's law of heat conduction, which indicates that the rate of heat transfer through a material is proportional to the temperature gradient across that material.

While the other factors mentioned might influence specific scenarios regarding heat transfer, they do not serve as the primary driving force for heat flow. For instance, the color of an object affects how much radiation it absorbs or reflects but does not dictate the flow of heat in every context. Similarly, while the area of contact between two objects can influence the rate of heat transfer (larger areas can facilitate more heat exchange), the underlying cause for the transfer lies in the temperature differences. Lastly, pressure differences in gases can affect heat transfer in certain situations, particularly during convection processes, but they are not the fundamental reason for heat flow like temperature differences are. Thus, the dependency on the temperature difference is the key factor in understanding heat transfer.