Heat Energy

The heat energy of a substance is determined by how active its atoms and molecules are. A hot object is one whose atoms and molecules are excited and show rapid movement. A cooler object's molecules and atoms will be less excited and show less movement. When these guys are in the excited state, they take up a lot of space because they're moving around so fast. When the atoms and molecules settle down, or cool down, they take up less space.




If a HOT high-energy atom comes into contact with a cool low-energy atom, the excited atom will loose some of its energy to the cool atom. The two atoms will settle into an energy level that's between where they each started out. That level is called Thermal Equilibrium. Did you know a lot of racecar drivers will let their engines cool down while idling before shutting it off after a hard race? They do this to let all of the internal engine parts come to Thermal Equilibrium.





Experiment: If you have a cup of really hot chocolate and want to cool it down, you may put and ice cube in the cup. After the ice completely melts, stir the chocolate. The hot chocolate and the melted ice have come to Thermal Equilibrium.


Bibliography:
http://www.powermasters.com/heat_energy.html