* New substances are formed: When gasoline (a mixture of hydrocarbons) burns, it reacts with oxygen from the air. This reaction produces carbon dioxide, water vapor, and other byproducts. These are entirely different substances from the original gasoline and oxygen.
* Bonds are broken and formed: The chemical bonds within the gasoline molecules and the oxygen molecules are broken. New bonds are formed to create the molecules of the products (carbon dioxide and water).
* Irreversible: The burning process is not easily reversible. You can't simply combine carbon dioxide and water to get back gasoline.
In summary: The burning of gasoline in an engine involves the creation of new substances with different chemical properties, signifying a chemical change.
