* New Substances are Formed: Combustion involves the reaction of the fuel with oxygen. This reaction breaks the original chemical bonds in the fuel and oxygen molecules and forms entirely new substances: carbon dioxide, water, and often ash or other byproducts.
* Irreversible Change: The combustion process cannot be easily reversed to get back the original fuel and oxygen. The chemical composition has permanently changed.
* Energy is Released: Combustion is an exothermic reaction, meaning it releases heat and light energy. This energy release is another indication of a chemical change.
In summary: The combustion of a fuel is a chemical change because it involves the formation of new substances, is irreversible, and releases energy.
