large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb_116
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_02_asimov_64kb
English
12904
This is true of all substances. For instance, hydrogen gas, as it is found on earth, is made up of molecules containing 2 hydrogen atoms each (H₂). Add a certain amount of energy and you pull the atoms apart; allow the atoms to come back together into paired molecules, and the added energy is given back again. THIS IS TRUE OF ALL SUBSTANCES FOR INSTANCE HYDROGEN GAS AS IT IS FOUND ON EARTH IS MADE UP OF MOLECULES CONTAINING TWO HYDROGEN ATOMS EACH SYMBOLIZED AS H TWO ADD A CERTAIN AMOUNT OF ENERGY AND YOU PULL THE ATOMS APART ALLOW THE ATOMS TO COME BACK TOGETHER INTO PAIRED MOLECULES AND THE ADDED ENERGY IS GIVEN BACK AGAIN
f 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. 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. If, after being pulled apart, the atoms are allowed to come together again, they give off energy. The amount of energy they give off in coming together is exactly equal to the amount of energy they had to gain before they could separate. URED 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 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 IF AFTER BEING PULLED APART THE ATOMS ARE ALLOWED TO COME TOGETHER AGAIN THEY GIVE OFF ENERGY THE AMOUNT OF ENERGY THEY GIVE OFF IN COMING TOGETHER IS EXACTLY EQUAL TO THE AMOUNT OF ENERGY THAT THEY HAD TO GAIN BEFORE THEY COULD SEPARATE
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