Through cooking eggs, investigate reversible and irreversible changes
Irreversible changes, like burning, cannot be undone. Reversible changes, like melting and dissolving, can be changed back again.
A change is called irreversible if it cannot be changed back again.
For example you cannot change a cake back into its ingredients again.
Irreversible changes are permanent. They cannot be undone.
In an irreversible change, new materials are always formed. Sometimes these new materials are useful to us.
Heating can cause an irreversible change. For example you heat a raw egg to cook it. The cooked egg cannot be changed back to a raw egg again.
Cooking eggs cannot be reversed back again.
Demonstrate this in class using an egg as an example of irreversible change and other food, such as chocolate, as an example of reversible change.