* New substances are formed: When paper burns, it reacts with oxygen in the air. This chemical reaction produces ash, carbon dioxide, water vapor, and other gases. These are entirely different substances from the original paper.

* Irreversible process: The burning of paper cannot be reversed to get the original paper back. The chemical bonds in the paper have been broken and rearranged, creating new substances.

In contrast, a physical change would involve a change in appearance or state, but not the formation of new substances. Examples of physical changes include:

* Tearing paper (change in shape)

* Folding paper (change in shape)

* Freezing water (change in state)