18. From Outer Space To Inner        Space   Previous PageNext Page

Plasmas have been described as a fourth state of matter, along with gases, liquids, and solids at lower temperatures. Electrons and nuclei from a plasma only combine to form atoms at temperatures below 100,000 degrees. Atoms in turn do not associate into molecules, nor do molecules condense into liquids and solids, until temperatures fall below a few thousand degrees. The delicate carbon compounds that we shall be examining in the following chapters break down a few dozen degrees above "normal" or room temperature, which can be assumed to be around 300K. In contrast, most familiar chemical reactions effectively come to a halt 100C below room temperature.

We saw in Chapter 15 that the rates of chemical reactions depend on energies of activation. A reaction with a modest activation energy of 11 kcal mole proceeds 10,000 times faster at 300 than at 200 , even assuming that it remains a gas-collision process at the lower temperature. If the reactants and products condense to liquids or solids, then the process at 200K is even slower. Just as the familiar physical world is encountered between 10 cm and 10 cm, so the familiar chemical world occurs primarily between 200K and 2000K. Life for some simple bacteria can go on as low as 255K or as high as 377K, but for the most advanced organism, man, the chemistry of life breaks down a short distance to either side of 310K or 37C. The more complex the machinery, the more restricted are its operating conditions.

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