* New substance formed: The resulting iron sulfide (FeS) is a completely different substance with different properties than iron (Fe) and sulfur (S). It has a different color, melting point, and chemical reactivity.
* Chemical bonds broken and formed: The chemical bonds holding the iron and sulfur atoms together in their original forms are broken. New chemical bonds are formed between iron and sulfur atoms to create the iron sulfide molecule.
Key characteristics of a chemical change:
* Formation of a new substance with different properties.
* Involves breaking and forming chemical bonds.
* Often difficult or impossible to reverse.
In contrast, a physical change only alters the appearance or state of a substance without changing its chemical composition. Examples include melting ice or cutting paper.
