Question

which refers to the thermal energy that flows from one substance to another when the substances differ in temperature?
heat
temperature
convection
flow

Explanation:

Heat is the transfer of thermal energy from a region of higher temperature to a region of lower temperature. Temperature is a measure of the average kinetic energy of the particles in a substance. Convection is a mode of heat transfer involving the movement of fluids. Flow is a general term for movement.

Answer:

heat