When you mix iron filings and sulfur, and then heat the mixture, you create iron sulfide. This is a chemical reaction where the iron and sulfur atoms combine to form a new substance with different properties than the original elements.

Here's why:

* Chemical Change: The process involves a chemical change because the atoms of iron (Fe) and sulfur (S) rearrange and bond to form a new compound, iron sulfide (FeS). This compound has a different chemical composition and properties from either iron or sulfur alone.

* New Substance: Iron sulfide has a distinct black color, a different melting point, and is magnetic, unlike sulfur which is non-magnetic.

* Chemical Reaction: The reaction between iron and sulfur is exothermic, meaning it releases heat, and often produces a bright glow.

The chemical equation for the reaction is:

Fe + S → FeS

This equation shows that one atom of iron reacts with one atom of sulfur to form one molecule of iron sulfide.