substance
Mixture
An element - substance - NOT a mixture.
a mixture
Reacting iron with sulfur an iron sulfide is formed, not a mixture.
You will have a mixture of zinc and iron filings.
Mixture
iron starts melting
Iron is a pure substance. It's an element (Fe) and a bar of Iron is no mixture. If it was pure iron, then by definition it would be pure. However iron is rarely pure, it is usually in alloy with something.
Forms the compound, iron sulfide.
Iron is an element. It is a pure substance that consists of only one type of atom, specifically iron atoms.
An iron sulfide is obtained: FeS2.
a screen