* Pure Substance: A pure substance is made up of only one type of molecule. In the case of ice, it's made entirely of water molecules (H₂O).

* Fixed Composition: The chemical composition of ice is always the same: two hydrogen atoms and one oxygen atom per molecule.

* Unique Properties: Ice has distinct physical and chemical properties that are different from the liquid form of water (water) or the gaseous form (water vapor).

While ice can contain impurities like dissolved minerals, it's still primarily a substance because its composition is dominated by water molecules.