The History of Heat

          Aristotle and the Greeks had their idea of fire as one of the 4 Primal Elements.   Even the ancients realized that heat and light were not alike as aspects of fire, though.   After the fire had gone out and the light gone, the heat of the kettle and its contents remained.

            First modern chemist to study heat was  Joseph Black (1728 - 1799).  Black tried to explain heat in terms of a fluid.  He explained how a kettle of water placed over a fire increased in temperature but a kettle filled with water and ice placed over a fire did not change in temperature till all the ice was melted.  He said that until the ice was saturated with the heat-fluid and thus became melted could its temperature rise.  Lavoisier accepted this theory and gave the name for this heat-fluid “caloric” from the Latin word for heat.

            Another idea competed with the caloric theory.  Scientist knew that kinetic energy of motion plus the stored energy called potential energy was given the name mechanical energy and that friction was a part of the conservation of these energies.  They knew friction could warm up an object so maybe the invisible motion of invisible particles was what we call heat. Summed up; friction was converting mechanical energy into heat. The problem was this idea of really small particles of matter (i.e., atoms and molecules).

            Count Rumford (really Benjamin Thompson - a spy for the British authorities during the Revolutionary War) was to supervise the boring of cannon for Bavarian army.  Using a horse to work a treadmill he realized that the solid block of brass grew hot as the borer cut its way in.  Rumford calculated that if the caloric theory were correct the heat released during the boring would have melted the entire block of metal first.  He pointed out that heat was produced without fire, without light, without chemical combustion.  It came just out of motion.

            John Dalton comes along with his ideas of atoms and the kinetic energy idea of heat began to gain favor.  An English physicist, James Prescott Joule (1818-1889) was attempting to find the mechanical equivalent of heat.  In the end he found that a given amount of energy of whatever form always yielded that same amount of heat (at 4.18 joules per calorie).  The relationship of the motion of atoms to temperature and heat was placed on firm theoretical basis about 1860 by the Scottish physicist James Clerk Maxwell.

Page Last Updated: Friday March 02, 2007           Webmaster: Larry Jones                 Pickens County School District