What process involves the direct transfer of heat from one touching substance to another?

The process that involves the direct transfer of heat from one substance to another that is in contact is conduction. This mechanism occurs through the collision of molecules within solids. When one substance is heated, its molecules move faster and collide with adjacent molecules, transferring kinetic energy from the warmer substance to the cooler one.

Conduction is most commonly observed in solids, where the particles are closely packed, allowing for efficient energy transfer. For instance, when a metal spoon is placed in hot water, the heat from the water moves into the spoon through conduction, causing the spoon to become warm.

In contrast, convection refers to the transfer of heat through the movement of fluids (liquids and gases), where warm areas of the fluid rise and cool areas sink, creating a circulation pattern. Radiation involves the transfer of heat through electromagnetic waves and does not require direct contact or a medium, like when warm sunlight heats the earth. Evaporation is the process where liquid turns into vapor and is associated with energy transfer in the form of heat as liquid molecules escape into the air.

Thus, the correct identification of conduction as the method of direct heat transfer between touching substances highlights its fundamental role in thermal interactions within materials.