A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilized. Can the change in POP be reversed?
No, the change in plaster of Paris cannot be reversed.
When water is added to POP, it undergoes a chemical change. Its composition changes and is converted into another substance. Since it is a chemical change, so it cannot be reversed. Making statues out of plaster of Paris is an irreversible change because plaster of Paris has a property of setting into a hard mass on getting mixed with water due to the formation of a new compound. The hard mass cannot be converted back into the previous plaster of Paris . Hence, it is an irreversible change.