Heat vs. Internal Energy

Do not confuse

heat

with

internal energy

!

Internal Energy


The total energy of the molecules within a system. This includes vibrational, rotational and translational energies. These forms of internal energy are sometimes called "sensible" because they change when the temperature changes. But, internal energy also includes the energies of molecular interactions, chemical bonds and nuclear energies.

At the molecular level, one mechanism for heat transfer is the collision of molecules that have different vibrational, rotational and translational energies.

Heat transfer is the flow of energy due to a difference in the sensible internal energy of molecules.

Heat

Heat exchange arrow

Cup of
hot tea

System boundary
2 kJ
heat
Surrounding Air
2 kJ
internal
energy
Cup of water.
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Ch 4, Lesson B, Page 3 - Heat vs. Internal Energy