Final answer:
Kinetic energy transfer occurs through particle collisions, with more energy transferred from high-temperature substances to low-temperature substances.
Step-by-step explanation:
Kinetic energy transfer occurs when particles collide with one another. In the majority of collisions, particles with greater kinetic energy transfer some of their energy to particles with lower kinetic energy. This transfer can happen in both directions but overall, more energy is transferred from the higher-temperature substance to the lower-temperature substance. When thermal equilibrium is reached, the energy transfer in both directions is, on average, the same.