Compare Physical Properties Retained in Mixtures Versus Compounds

The behavior of physical properties is a primary way to distinguish between mixtures and compounds. In short, mixtures are the "sum of their parts," while compounds are entirely new substances.

Mixtures: Properties Are Retained

In a mixture, the components keep their original physical and chemical properties. The mixture's properties are a blend of the components and can vary based on the mixing ratio.

• Example: A Mixture of Iron Filings and Sulfur Powder
  • The iron filings remain grey and magnetic.
  • The sulfur powder remains yellow and non-magnetic.
  • You can use a magnet (exploiting iron's property) to separate them.
  • If you add the mixture to water, the sulfur (less dense) may float, and the iron (denser) will sink.

Compounds: New Properties Are Formed

When a compound forms, a chemical reaction creates a brand-new substance with a unique set of properties that are different from the original elements.

• Example: The Compound Iron(II) Sulfide (FeS)
  • If you heat the mixture of iron and sulfur, they react to form the compound FeS.
  • This new substance is a black, brittle solid.
  • Crucially, it is non-magnetic. The original magnetic property of iron is lost.
  • The new compound has its own specific density and melting point, different from both iron and sulfur.