An example of a teaching analogy:
"When enough activation energy is added, the reacting molecules interact very closely with each other to produce the activated complex. It is an aggregate of particles which has a higher potential energy than either reactants or products, and represents an intermediate stage or situation that must be reached before the reaction will proceed to produce the products.
A fire fighting analogy can be used to illustrate this idea. If firemen wish to access a fire on the second floor of a building, they can't enter if they just climb up the ladder so their feet are at the level of the second floor. They must climb a little higher, to a higher potential energy location, so that their feet are at the level of the window sill; then they can climb in and drop down to floor level to complete their entry.
In reverse, the firemen can't go from the second floor directly to the ground; they must first climb up to the window sill then go down their ladder to the ground. In both cases the window sill, just like the activated complex, represents a specific higher energy stage that must be reached in order to move from the original to the final situation."
Previously posted at scienceanalogies.com by retired science teacher Murray Hart – original source: Licata, Kenneth P. Chemistry Is Like a … Science Teacher 1988, 55(8), 41
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