What is the difference between a reversible and non-reversible change?
As the name suggests, a reversible change is one where the change or the process can be reversed and we can get back the reactants in their original condition. In comparison, a non-reversible change causes irreversible changes in the reactants and we end up with a product which can not (on its own) convert back to reactants.
An example of a reversible change is mixing salt into water. We end up with salty water, which can be converted back to water and salt by evaporating (and collecting the water vapors) the water from the solution. Similarly, a mixture of apples and oranges can segregated. In comparison, once we cook food, we cannot convert it back into its ingredients. Growth is also an example of non-reversible change, since once we grow, we cannot go back to our previous size.
Hope this helps.