What is heat transfer called when substances of different temperatures are in contact?

The process of heat transfer that occurs when substances of different temperatures are in direct contact is known as conduction. This is because conduction involves the transfer of heat through a material without any overall movement of the material itself. When two objects at different temperatures come into contact, heat energy from the hotter object is transferred to the cooler one, resulting in a balance of temperature over time.

In conduction, the heat transfer occurs at the molecular level as faster-moving (hotter) molecules collide with slower-moving (cooler) molecules, passing along their energy. This process continues until thermal equilibrium is reached.

The other processes: convection involves the movement of fluids (liquids or gases) and the transfer of heat through the flow of the fluid, radiation refers to heat transfer through electromagnetic waves without the need for a medium (like the heat from the sun), and insulation is a method or material used to reduce the rate of heat transfer. Therefore, conduction is the specific term that describes heat transfer through direct contact between substances at different temperatures.