The total energy of motion in the particles of a substance; heat energy.

• A. Mechanical energy
• B. Thermal energy
• C. Light energy
• D. Sound energy

Answer: (B)

Thermal energy is the total energy tied to the microscopic motion and interactions of particles inside a substance. The temperature of a substance reflects the average kinetic energy of its particles, and heat is the transfer of this energy between objects due to a temperature difference. This description—energy associated with the motion of particles within a material, related to heat energy—fits thermal energy best.

Mechanical energy involves macroscopic motion and position of objects, not the internal motion of particles. Light energy comes from electromagnetic radiation, and sound energy comes from vibrating particles that produce waves.