* Chemical Change: Involves the formation of new substances with different chemical properties.

* Physical Change: Alters the form or appearance of a substance but not its chemical composition.

How tarnishing is a chemical change:

* Example: When silver tarnishes, it reacts with sulfur in the air to form silver sulfide (Ag₂S). This new compound, silver sulfide, is black and has different properties than pure silver.

* Formation of new substance: The original silver metal is transformed into silver sulfide, a new substance.

* Chemical reaction: The process involves a chemical reaction between silver and sulfur.

Therefore, tarnishing is a chemical change because it involves the formation of a new substance (silver sulfide) through a chemical reaction.