Iron Sulfide Formation: Chemical Change Explained

Explanation of the Reaction

When iron filings (Fe) are mixed with sulfur powder (S) and heated, a chemical reaction occurs. This reaction forms a new substance called iron sulfide (FeS). Iron sulfide has distinct physical and chemical properties that are different from both iron and sulfur.

The process involves the rearrangement of atoms and the formation of new chemical bonds. Heating provides the necessary activation energy for this reaction to proceed. Because a new substance with new properties is formed, this is classified as a chemical change.

Analyzing the Changes Involved

• Identifying Chemical Change: The key indicator of a chemical change is the formation of a new substance. In this case, iron sulfide (FeS) is produced, which is chemically different from the starting materials, iron (Fe) and sulfur (S).
• Distinguishing from Physical Change: Physical changes alter the form or appearance of a substance but not its chemical composition. Examples include mixing, melting, or boiling. Simply mixing iron and sulfur without heating results in a physical mixture, but heating initiates a reaction.
• Evaluating Option 3: Dissolving iron in sulfur to form a solution is a physical process. However, the heating causes a chemical reaction, not just dissolution, resulting in a compound (FeS) rather than a solution.
• Confirming Correct Description: Option 4 accurately describes the event as a chemical change because a new substance, iron sulfide, is formed from the reaction between iron and sulfur.

Conclusion

The transformation of iron and sulfur into iron sulfide upon heating is a classic example of a chemical change due to the creation of a new chemical compound.