Question #98920

1 Answer
Dec 13, 2016


Careful Kaleb! It can be misleading to use reversibility as a defining characteristic of physical changes. There are many chemical changes that are reversible. It largely depends on how much "damage" gets done to molecules during the change.


Essentially, any change can be reversible, provided it is possible to "rebuild" the original molecules out of the products we obtained once the change was complete.

In general, physical changes do not cause molecules to be broken apart and rearranged into new combinations as is the defining characteristic of a chemical change. Because of this, it is generally possible for a simple effect like a temperature change to restore the molecules to there original configuration. Thus, solids melt, and liquids freeze, but the molecules are simply changed in arrangement rather than structure.

Even in chemical changes, if the "damage" done to molecules has not been too extensive and the molecules are fairly simple, it can be possible to rebuild them and in doing so, run the reaction in reverse! This is just what happens when we recharge a battery, for example.
On the other hand, when we fry an egg, the changes to the proteins are so complex, that it is not possible to "undo" it, and the reaction is irreversible.