Sinhyu/iStock/GettyImages
An aqueous solution is a mixture in which water serves as the solvent and dissolves one or more solutes. While water is most commonly encountered as a liquid at room temperature, it also exists in solid (ice) and gaseous (vapor) states.
In chemical notation, a substance dissolved in water is marked with the suffix (aq). For example, sodium chloride in water is written as NaCl(aq), whereas solid salt is denoted by NaCl(s). The dissociation of the salt into its constituent ions is represented as Na⁺(aq) + Cl⁻(aq).
Only hydrophilic compounds—those that attract water—dissolve readily in aqueous media. Acids, bases, and many salts fall into this category. Hydrophobic substances, such as oils and fats, exhibit limited solubility in water.
When electrolytes dissolve, the released ions make the solution electrically conductive. Non‑electrolytes, like sucrose, remain intact at the molecular level and therefore do not conduct electricity.
Aqueous solutions are central to countless chemical processes, from industrial synthesis to biological function. In pure water, the scarcity of ions means it conducts electricity poorly. Once a solute dissociates into ions, the resulting electrolyte solution can conduct electric current efficiently.
Strong acids and bases, such as hydrochloric acid or sodium hydroxide, fully dissociate in water, yielding strong electrolytes that enhance conductivity. Weak electrolytes partially dissociate, producing fewer free ions and thus lower conductivity.
A liquid is defined by its ability to flow, maintain a definite volume, and adapt its shape to any container. Water at ambient temperature exemplifies these properties. An aqueous solution, however, is a specific type of liquid where water is the solvent. While all aqueous solutions are liquids, not all liquids are aqueous.
Key properties of liquids include:
