The Best Analogy Ever (part 1)

In order for chemical reactions to occur they usually need a little help. This help comes in the form of activation energy.  Burning is a familiar chemical reaction.  If you look around just about everything you see could burn, but it doesn’t.  The stuff doesn’t spontaneously combust because the molecules that make them are bound together in relatively stable forms.  The rug is made of rug molecules that are chosen for their stability (though the rug store would likely sell more rugs if they simply dissolved into the universe but on the other hand they probably wouldn’t sell any rugs once the word got out about their instability).  Either way, under normal circumstances the rug will passively lie on the floor for a long, long time. Unless…activation energy. 

In the case of the rug the activation energy could come in the form of a tipped candle or a smoldering cinder from a fireplace but, with just enough heat, the rug will burn.  Once the burn reaction has started it will provide the heat for the adjacent rug area and the reaction will spread.  Eventually the fire might spread to the couch, the cabinet, the walls and eventually the whole house will be up in flames.

This may seem obvious but the important point is that the raging inferno was started by a tiny flame, just enough energy, to get it going.  Activation energy is the little push that gets reactions moving but it is also the best analogy ever.