What is thermal energy?

Thermal energy refers to the total kinetic energy of the particles within a substance. This includes the energy associated with the motion of atoms and molecules, which increases as the temperature of the substance rises. When a substance is heated, the particles move more vigorously, resulting in a higher total kinetic energy, which directly relates to the concept of thermal energy. This understanding is fundamental in the study of thermodynamics and explains many physical processes, such as heat transfer and changes in state.

The other options, while related to concepts in thermodynamics, do not accurately define thermal energy. For instance, the energy from chemical bonds is more closely associated with potential energy rather than kinetic energy. Energy transfer due to radiation pertains to the mechanism by which heat can move from one object to another, rather than defining thermal energy itself. Lastly, the energy required to change the temperature of a substance speaks to specific heat capacity, which is not the same as the total thermal energy of the substance at a given moment.