Mixture vs Compound: A Case Study
We take two elements: Iron filings (Grey, Magnetic) and Sulfur powder (Yellow, Non-magnetic).
Part A: Physical Mixture (Sample A)
Mix Iron filings and Sulfur powder in a dish. Do not heat.
- Appearance: Yellow powder with grey specks visible (Non-uniform).
- Magnet Test: If you bring a magnet, Iron filings are attracted and separated. Sulfur remains.
- Acid Test: Add dilute HCl. Hydrogen gas evolves (pop sound).
- Reason: Iron reacts with acid, Sulfur does not.
- Conclusion: Components retain their properties. This is a Mixture.
Part B: Chemical Compound (Sample B)
Heat the mixture strongly until it glows and turns into a black mass. Cool and grind it.
- Appearance: Uniform black mass (Iron Sulfide).
- Magnet Test: No attraction. Iron has lost its magnetic property.
- Acid Test: Add dilute HCl. Hydrogen Sulfide () gas evolves (smells like rotten eggs).
- Reason: The compound reacts to form a new gas.
- Conclusion: Properties have changed completely. This is a Compound.
Summary Table
| Property | Mixture (Fe + S) | Compound (FeS) |
|---|---|---|
| Separation | Possible by magnet | Not possible by magnet |
| Properties | Shows properties of Fe (magnetic) and S | Properties are different (non-magnetic, black) |
| Reaction with Acid | Hydrogen Gas () | Hydrogen Sulfide Gas () |
| Composition | Any ratio | Fixed ratio |