Aqueous
Summary: A substance dissolved in water, shown by the state symbol (aq). Tags: igcse chemistry keyword Created: 2026-08-06
An aqueous substance is one that has been dissolved in water, forming a solution. In chemical equations it is shown with the state symbol (aq) — for example, in the reaction between hydrochloric acid and sodium hydroxide, the soluble reactants are written as HCl(aq) and NaOH(aq). A substance is described as aqueous when water is the solvent, as opposed to solid (s), liquid (l) or gas (g) states.
A key IGCSE exam point is that aqueous solutions can conduct electricity if the solute is ionic. When an ionic compound such as sodium chloride dissolves in water, it dissociates into separate ions (Na⁺ and Cl⁻) that are free to move through the solution. These mobile ions carry the charge, so the solution conducts. Covalent molecular solutes like sugar dissolve without forming ions, so their solutions do not conduct electricity.
Sources
- Cambridge IGCSE Chemistry 0620 Syllabus (2023-2025), Cambridge Assessment International Education
Common Misconceptions
| Misconception | Reality |
|---|---|
| (aq) means the substance is a liquid | (aq) means the substance is dissolved in water; the substance itself may be solid, liquid or gas (e.g. CO₂(aq)) |
| Aqueous and liquid states are the same | A liquid is pure substance in liquid state; an aqueous solution is a mixture of solute and water |
| All aqueous solutions conduct electricity | Only solutions containing free-moving ions (usually from ionic solutes) conduct; covalent solutes like sugar do not |