What is true about heat transfer by conduction?

Heat transfer by conduction is a process where thermal energy moves through a material due to a temperature difference, typically occurring in solids. In this mode of heat transfer, kinetic energy is transferred between adjacent molecules when one part of a solid is heated. For instance, if one side of a metal bearing is heated, the energy will propagate through the solid material to the cooler side.

This method is particularly effective in solids because they have closely packed molecules that can readily interact and transfer energy. Unlike liquids and gases, where heat transfer also occurs but often involves convection or conduction to a lesser extent, solids facilitate efficient conduction due to their molecular structure.

The other choices suggest misconceptions about conduction; for example, heat transfer does occur in solids, and conduction does not require a vacuum; it can effectively occur in any solid material without the need for any specific environmental conditions.