Iron and Sulfur Compound Formation

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Compounds, Elements and Periodic Table, Mixtures and Separation

Alternative titles: Mixture vs Compound Demonstration

Summary

his demonstration shows the difference between a physical mixture and a chemical compound. Iron filings and sulfur powder can be mixed together and separated with a magnet, but when heated, they react to form iron sulfide, a compound that cannot be separated by physical means.

Procedure

Combine iron filings and sulfur powder in a container and mix well to form a heterogeneous mixture.
Demonstrate separation of the mixture using a magnet, which attracts the iron while leaving the sulfur behind.
Place the mixture in a test tube or beaker and heat strongly over a bunsen burner, hot plate, or stove.
Observe the glowing reaction as iron and sulfur combine to form iron sulfide (FeS).
After cooling, show that the resulting compound cannot be separated with a magnet.

Links

Iron and sulphur as elements, a compound and a mixture - Sci-sphere:

Iron + Sulfur - Scott Milam:

📄 How To Make a Mixture and a Compound from Iron and Sulfur - ThoughtCo: https://www.thoughtco.com/make-mixture-compound-iron-and-sulfur-606308

Variations

Vary the ratio of iron to sulfur to demonstrate leftover reactants after the reaction.
Compare physical properties (magnetism, color, texture) of the mixture versus the compound.
Use different heating methods (bunsen burner, hot plate) to illustrate practical lab setups.

Safety Precautions

Wear safety glasses and gloves.
Perform heating in a well-ventilated area or under a fume hood to avoid inhaling sulfur fumes.
Use only small quantities to prevent excessive heat or splattering.
Dispose of iron sulfide safely according to local regulations.

Questions to Consider

Why can a magnet separate iron from the mixture but not from iron sulfide? (In the mixture, iron retains its metallic properties, but in the compound, iron is chemically bonded to sulfur.)
What visual changes indicate that a chemical reaction has occurred? (Glowing, color change, loss of magnetism, formation of a new solid.)
How do mixtures differ from compounds in terms of composition? (Mixtures can have variable ratios and be separated physically, while compounds form in fixed ratios and require chemical reactions to separate.)