What is Thermal Energy?

• A. The energy of motion
• B. The energy of particle motion in matter; felt as heat
• C. The energy of light traveling in waves
• D. The energy that powers machines

Answer: (B)

Thermal energy is the energy tied to the motion and interaction of the particles inside matter. All the tiny particles—atoms and molecules—are jigging and pulling on one another, so their kinetic and potential energies add up to the substance’s internal energy. When you feel heat, that’s the thermal energy being transferred or experienced as a result of temperature differences. It’s not the energy of motion for a single object (that’s kinetic energy), not energy carried by light, and not the energy that powers machines. The total thermal energy grows when the particles move faster (higher temperature) and when there are more particles present, since there’s more energy packed into the substance overall.