Final answer:
The kinetic theory explains that heat is due to the motion of molecules, with thermal energy being the total kinetic energy of moving atoms and molecules.
Step-by-step explanation:
The kinetic theory explains the thermal behavior of gases and other forms of matter by stating that heat is due to the motion of molecules. According to this theory, the thermal energy of matter is the total kinetic energy due to the movement of its atoms and molecules. Temperature, an intensive property, corresponds to the average kinetic energy of these particles. When objects at different temperatures come into contact, heat is transferred from the warmer object to the cooler one until thermal equilibrium is reached, without work being done in the process.