* Chemical Change: Burning involves a chemical reaction where natural gas (primarily methane) reacts with oxygen in the air. This results in the formation of new substances, carbon dioxide and water.

* Irreversible: The process of burning cannot be reversed easily. You can't turn carbon dioxide and water back into methane and oxygen without a significant energy input.

* Change in Composition: The chemical composition of the substances involved changes fundamentally during burning. Methane and oxygen become carbon dioxide and water.

In contrast, a physical property is something that can be observed or measured without changing the chemical composition of the substance. Examples include color, density, boiling point, etc.