You show a substance is dissolved in water when writing an equation by using the symbol (aq) after the chemical formula of the substance.

Here's how it works:

* (aq) stands for aqueous, meaning the substance is dissolved in water.

* For example, if you want to represent the dissolving of sodium chloride (NaCl) in water, you would write:

NaCl(s) → Na+(aq) + Cl-(aq)

* This equation indicates that solid sodium chloride (NaCl(s)) dissolves in water to form sodium ions (Na+(aq)) and chloride ions (Cl-(aq)) in solution.

Here are some other examples:

* Sugar dissolving in water:

C12H22O11(s) → C12H22O11(aq)

* Hydrochloric acid (HCl) dissolving in water:

HCl(g) → H+(aq) + Cl-(aq)

Important note: The state symbols (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous are used to indicate the physical state of the substance in the reaction.