Kinetics—A Veritable Explosion

you blessed innocent .. . Life will no longer be tranquil with a girl of nineteen round the place. You may fool yourself, but you can t fool me. A girl of nineteen doesn t REACT toward things. She explodes. Things don t react anywhere but in Boston and in chemical laboratories. I suppose you know you re taking a human bombshell into the arsenal  

Thermodynamics, as noted earlier, deals with the effects of heat and entropy on equilibrium and is useful for predicting the extent to which a reaction will occur. But like an obstreperous child avoiding chores, thermodynamics may tell you the reaction will take place, but not when. For example, thermodynamics predicts that graphite is a more stable form of pure carbon than diamond, so all diamonds will eventually turn to graphite. But before you start adjusting your investment portfolio, be advised that this transition may take billions of years. 

The word kinetics implies movement—as in kinetic art or kinesiology, the study of human muscles and motion. The word kinetics was chosen to describe the study of reaction rates because reaction rates rely on the movement of molecules. Scientists have been measuring reaction rates since at least the mid-1800s in Europe, but the explanations of the observed rates had to wait for the general acceptance of a theory of molecular motion. The kinetic theory of molecular motion states that molecules and atoms are always in motion, though the motion may be as subtle as the vibrations of ions in a crystal lattice or as frenzied as gas-phase molecules clocking around 1,640 feet (500 meters) in one second. 

At normal atmospheric pressures, however, the distance traveled by a gas molecule in one second would not be in a straight line the density of atmospheric molecules under normal terrestrial conditions is such that one molecule in the gas phase will experience some seven billion collisions in each second. All these collisions are good news for chemists who study reaction rates because the rate of collision is related to the rate of reaction before anything else can happen in a reaction, molecules must first come together. They must collide. 

The idea that reaction rates are tied to the rate of collision is aptly called the collision theory of reaction rates. But nature s mysteries are not so easily solved. During a chemical reaction, the electron orbitals (that is, the electron clouds) on individual reactants overlap and coalesce, the way two bubbles come together and merge into one. Once the conditions are right, it takes about a quadrillionth of a second for the electrons in the individual orbitals to readjust themselves into the orbitals around the products. But if all reactions took place as fast as collisions, then food would cook before 

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