Dissociation

Each molecule of water (H₂O) is made of two hydrogen atoms and one oxygen atom.

Unless they are frozen into ice, water molecules don’t always stay stuck together. When in liquid form, they are always splitting apart then reforming again. This is called dissociation. H₂O splits into two ions: OH^– (or hydroxide) ions and H⁺ (hydrogen ions; sometimes also called protons).