1. Pure substances are defined as substances that are made of only one type of atom or molecule.
2. The purity of a substance is the measure of the extent to which a given substance is pure.
3. The physical properties of a pure substance include well-defined melting and boiling points.
4. Elements are mostly metals, non-metals or metalloids.
5. Compounds, on the other hand, are also pure substances when two or more elements are combined chemically in a fixed ratio.
