EQUILIBRIUM ANALOGIES

Entropy is an important factor in discussing equilibrium. Either the forward or reverse reaction will be favoured by the entropy factor ... that is, allowing atoms and molecules to move from a state of lesser to greater disorder.

Imagine taking a small box and into it packing marbles so that all the marbles in each horizontal layer are the same color, or show some other definite pattern. When the box is shaken for a while then the contents examined, you will see that the marbles are now quite randomly arranged ... they have spontaneously moved to a state of greater disorder (higher entropy).

Source: Smoot, R.C., Price, J. and Smith, R.G. Chemistry A Modern Course Don Mills: Maxwell Macmillan Canada, 1987, p.386

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Equilibrium is a situation attained when the rates of forward and reverse reaction are equal, so that there is no change in the concentrations of the reactants and products. Equilibrium can be reached at various points; the concentrations of reactants and products need not be equal, only their rate of exchange. The equilibrium point also shifts in response to stresses placed upon the system.

In a sports game like soccer or basketball, for every new player substituted onto the field, an old player must leave - thus the rate of these opposing reactions are equal. There is no change in the number of players on the field, even though their identities are different. There is no requirement that the number of players on the field and on the bench be equal (and usually they are not equal); the only thing that must be equal is the rate of exchange between these two groups.

In a game like hockey, a penalty would be like a stress ... it increases the number of players leaving the ice, compared to the number of players going onto the ice. At this new equilibrium point the rate of player exchange is again equal for the duration of the penalty. When the penalty is over, the equilibrium point shifts back to the original position.

Source: Licata, Kenneth P. Chemistry Is Like A ... The Science Teacher 1988, 55(8), 43.

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