Question

You accidently dropped your favourite toy and broke it. This is a change you did not want. Can this be reversed?

Answer 1

Hint: A physical change changes the physical properties of a substance. If we can restore the original form of the substance after the change then the change is considered reversible otherwise it is irreversible.

Complete answer:
We know that change is an act or a process through which something becomes different. In chemistry, there are physical and chemical changes.
We can define physical change as the change which affects the form of a chemical substance but does not change its chemical composition. Basically we can say that the change in the physical properties of a substance is a physical change. The physical property of a substance includes its volume or mass, density, flexibility, its colour and texture. Examples of physical change are boiling of milk or stretching of a rubber band.
 We can define a chemical change as the change which causes a substance to change its composition and result in the formation of a totally new substance. For example we can take rusting of iron or curdling milk.
In simple words we can say that physical change is the change in the appearance of a substance and not its composition and a chemical change is the change in the chemical structure of the substance and forming a totally new substance with a different chemical formula.
These changes can either be reversible or irreversible. If we can get back the starting substance after it has undergone a change then the change is reversible and if we get a substance which cannot be reverted back to the original substance then the change is irreversible. For example if we stretch a rubber band and then leave it, it reverts back to its original form thus it is a reversible change whereas curdling of milk on adding a drop of lemon is an irreversible process.
Generally, a physical change is reversible but a chemical is irreversible. However, in some chemical changes we can get back the original substance but this also includes further chemical changes.
In the question we have breaking of a toy. Here, there is no change in the chemical composition of the broken toy so this is a physical change but the original form of the toy cannot be restored. Therefore, this process cannot be reversed. It is an irreversible physical change.

Note:
Generally, chemical changes are irreversible but a reversible chemical change is a change where the reactants and the products both are at equilibrium. Once equilibrium is reached, the reaction can move either way. The reactants can change into products and the product can also change back into the reactants.