State the characteristics of chemical changes.

The characteristics of a chemical change can be summarized as follows :

1. New substance(s) is/are formed.
2. The composition of the original substance changes completely.
3. The change is permanent and irreversible.
4. There is a change in the mass of the original substance.
5. There is an exchange of energy during a chemical change which means that energy in the form of heat and light may be released or absorbed.