How To Make a Mixture and a Compound from Iron and Sulfur

A mixture occurs when you combine matter so that the components can be separated again. A compound results from a chemical reaction between components, forming a new substance. For example, you can combine iron filings with sulfur to form a mixture. All it takes is a magnet to separate the iron from the sulfur. On the other hand, if you heat the iron and sulfur, you form iron sulfide, which is a compound; the iron and sulfur can no longer be separate from one another.

What You Need

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By Anne Marie Helmenstine, Ph.D.

• Iron filings
• Sulfur (powder or flowers of sulfur)
• Magnet
• Test tube or beaker
• Burner or hot plate or stove

Creating a Mixture and Then a Compound

1. First form a mixture. Stir some iron filings and sulfur together to form a powder. You have just taken two elements and combined them to form a mixture. You can separate the components of the mixture by stirring the powder with a magnet; the iron filings will stick to the magnet while the sulfur will not. Another (less messy) option is to swirl the powder with the magnet under the container; the iron will fall toward the magnet at the bottom.
2. If you heat the mixture over a bunsen burner, hot plate, or stove, the mixture will start to glow. The elements will react and will form iron sulfide, which is a compound. Unlike the mixture, the formation of a compound can't be undone so easily. Use glassware that you don't mind ruining.

When you form a mixture, you can add components in any ratio that you want. It doesn't matter if there is more iron than sulfur, for example.

When you form a compound, the components react according to a set formula. If there is an excess of one or the other, it will remain after the reaction that forms the compound. For example, you may have some leftover iron or sulfur in the tube with your mixture. Two grams of sulfur with 3.5 grams of iron filings will completely react.