Thermal energy

[1] It can denote several different physical concepts, including: Mark Zemansky (1970) has argued that the term “thermal energy” is best avoided due to its ambiguity.

He suggests using more precise terms such as “internal energy” and “heat” to avoid confusion.

[7] In a body of material, especially in condensed matter, such as a liquid or a solid, in which the constituent particles, such as molecules or ions, interact strongly with one another, the energies of such interactions contribute strongly to the internal energy of the body.

Still, they are not immediately apparent in the kinetic energies of molecules, as manifest in temperature.

[8] In a statistical mechanical account of an ideal gas, in which the molecules move independently between instantaneous collisions, the internal energy is just the sum total of the gas's independent particles' kinetic energies, and it is this kinetic motion that is the source and the effect of the transfer of heat across a system's boundary.