Which of the following describes conduction?

Conduction is the process of heat transfer that occurs through direct contact between materials. When two objects at different temperatures touch each other, heat will flow from the hotter object to the cooler one until thermal equilibrium is reached. This transfer happens at the molecular level, as the faster-moving molecules of the hotter object collide with the slower-moving molecules of the cooler one, transferring energy in the process.

The other descriptions pertain to different modes of heat transfer. For example, heat rising due to air movement describes convection, where warmer, less dense air rises and cooler, denser air sinks to create a circulation pattern. The transfer of heat through empty space refers to radiation, which relies on the emission of energy in the form of electromagnetic waves. Lastly, heat transfer through liquids and gases is also a characteristic of convection, not conduction. Understanding these distinctions is essential for grasping the various methods by which heat can be transferred in different contexts.