large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb_33
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb
English
12904
Within the molecules, the atoms stick together more or less tightly. It takes a certain amount of energy to pull a molecule apart into separate atoms against the resistance of the forces holding them together. WITHIN THE MOLECULES THE ATOMS STICK TOGETHER MORE OR LESS TIGHTLY IT TAKES A CERTAIN AMOUNT OF ENERGY TO PULL A MOLECULE APART INTO SEPARATE ATOMS AGAINST THE RESISTANCE OF THE FORCES HOLDING THEM TOGETHER
 of bringing about any kind of work. Set it on fire, however, and the wood plus the oxygen in the air will give off heat and light that are clearly forms of energy. The heat could help boil water and run a steam engine. The amount of energy in burning wood could be measured if it were mixed with air and allowed to burn in a closed container that was immersed in a known quantity of water. From the rise in temperature of the water, the quantity of energy produced could be measured in units called “calories” (from a Latin word for “heat”). The instrument was therefore called a “calorimeter”. In the 1860s the French chemist Pierre Eugène Marcelin Berthelot (1827-1907) carried through hundreds of such determinations. His work and similar work by others made it clear that such “chemical energy”—the energy derived from chemical changes in matter—fit the law of conservation of energy. Here’s how it looked in the last decades of the 19th century. Molecules are composed of combinations of atoms. OF WORK SET IT ON FIRE HOWEVER AND THE WOOD PLUS THE OXYGEN IN THE AIR WILL GIVE OFF HEAT AND LIGHT THAT ARE CLEARLY FORMS OF ENERGY THE HEAT COULD HELP BOIL WATER AND RUN A STEAM ENGINE THE AMOUNT OF ENERGY IN BURNING WOOD COULD BE MEASURED IF IT WERE MIXED WITH AIR AND ALLOWED TO BURN IN A CLOSED CONTAINER THAT WAS IMMERSED IN A KNOWN QUANTITY OF WATER FROM THE RISE AND TEMPERATURE OF THE WATER THE QUANTITY OF ENERGY PRODUCED COULD BE MEASURED IN UNITS CALLED CALORIES FROM A LATIN WORD FOR HEAT THE INSTRUMENT WAS THEREFORE CALLED A KALORIMETER IN THE EIGHTEEN SIXTIES THE FRENCH CHEMIST PIERRE EUGENIE MARSILINE BERTHELLOT EIGHTEEN TWENTY SEVEN AND NINETEEN O SEVEN CARRIED THROUGH HUNDREDS OF SUCH DETERMINATIONS HIS WORK AND SIMILAR WORK BY OTHERS MADE IT CLEAR THAT SUCH CHEMICAL ENERGY THE ENERGY DERIVED FROM CHEMICAL CHANGES IN MATTER FIT THE LAW OF CONSERVATION OF ENERGY HEARS HOW IT LOOKED IN THE LAST DECADES OF THE NINETEENTH CENTURY MOLECULES ARE COMPOSED OF COMBINATIONS OF ATOMS
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