Thermal energy and heat are often confused. Rightly so because they are physically the same thing. Heat is always
the thermal energy of
some system. Using the word heat helps physicists to make a distinction relative to
the system they are talking about.
Heat: Term used to describe the transfer of thermal energy between two thermodynamic systems at
different temperatures.
Take a small piece of ice out of your fridge and hold it in your hand. The thermal energy content of your hand is
higher then the thermal energy content of the ice cube.
The atoms that comprise your hand are moving more
rapidly then the atoms that make up the ice cube. Therefore, there will be a transfer of thermal energy from
your hand to the ice cube. While this thermal energy is
in transfer, it is called heat. This will cause the atoms in
the ice cube to
speed up while the atoms in your hand
slow down.
The increase in speed of the ice cube atoms
changes the state of water from solid to liquid. This transfer of thermal energy will continue until an equilibrium is reached
between your hand, the ice (now water), and the air in the room.
When you put your hand over a hot stove you can feel the heat. You are feeling thermal energy
in transfer.
The atoms and molecules in the metal of the burner are moving very rapidly because
the electrical energy from the wall outlet has increased the thermal energy in the burner.
We all know what happens when we rub our hands together. Our mechanical energy increases the thermal energy content of the atoms
in our hands and skin. We then
feel the consequence of this - heat.
