* Compound: A pure substance formed by the chemical combination of two or more elements in a fixed ratio. For example, sulfuric acid (H₂SO₄) itself is a compound.

* Mixture: A combination of two or more substances where each substance retains its own chemical identity.

Dilute sulfuric acid is made by mixing concentrated sulfuric acid (H₂SO₄) with water. The sulfuric acid molecules are dispersed throughout the water, but they don't chemically react to form a new compound. The resulting solution contains both water molecules and sulfuric acid molecules.

Important Note: Diluting concentrated sulfuric acid is a highly exothermic reaction (releases a lot of heat). Always add acid to water slowly and carefully, never the other way around!