Which form of heat transfer involves direct contact between materials?

Conduction is the form of heat transfer that requires direct contact between materials. In conduction, heat is transferred through collisions between particles within a material or between materials that are in direct contact. When one part of a material is heated, the particles in that area gain energy and vibrate more rapidly. These energized particles collide with neighboring particles, transferring some of their energy and causing those particles to vibrate more as well. This process continues through the material until the heat is distributed evenly.

In contrast, convection involves the transfer of heat through the movement of fluids (liquids and gases) where warmer areas rise and cooler areas sink, creating a circulation pattern. Radiation, on the other hand, is the transfer of heat through electromagnetic waves and does not require any medium or direct contact. The term "leverage" does not relate to heat transfer and is not a recognized method of heat transfer in physics. Thus, conduction is the correct choice, as it is characterized by the necessity of contact for heat transfer to occur.