1.   In Pomerania this reaction took the form of an even tighter grip on the feudal peasantry and serfs of the great estates.

2.   Protein molecules called enzymes are machines in the sense that each one causes a particular chemical reaction to take place.

3.   The activation energy for a reaction is the minimum energy which colliding molecules require for a reaction to take place.

4.   However, these reactions only take place because of the presence of manufactured chlorine in the stratosphere.

5.   Initially his reaction took the form, from an early age, of a series of not always well-chosen amorous adventures.

6.   But for that reaction to take hold in the Clinton White House first required that the president himself realize that wrapping himself in green would pay off politically.

7.   But this reaction would take too long to be effective for most pollution and would not remove contaminating particles.

8.   In the case of babies, whose immune systems are not as developed as those of adults and older children, the reaction never even takes place.

9.   Most biological reactions take place in several small steps, each one designed to use energy efficiently.