* Element: A pure substance made up of only one type of atom (e.g., gold, oxygen, carbon).

* Compound: A substance formed when two or more different elements chemically combine in a fixed ratio (e.g., water, H₂O, is made of hydrogen and oxygen).

* Mixture: A combination of two or more substances where each substance retains its own properties (e.g., salt and pepper).

Distilled water is formed by the chemical combination of hydrogen and oxygen atoms in a 2:1 ratio (H₂O). This chemical bond creates a new substance with properties distinct from hydrogen and oxygen alone.