* New substances are formed: When fuel burns, it reacts with oxygen in the air. This chemical reaction produces new substances, primarily carbon dioxide, water, and energy (heat and light). The original fuel and oxygen are no longer present in their original forms.

* Irreversible: The burning process cannot be easily reversed to get back the original fuel and oxygen. The chemical bonds have been broken and new ones formed.

* Release of energy: The burning process releases energy in the form of heat and light, a characteristic of chemical reactions.

In contrast, a physical change involves a change in form or appearance, but not the chemical composition of a substance. Examples of physical changes include melting ice, cutting paper, or dissolving sugar in water.