Final answer:
In chemical equations, the symbols used to represent the physical states of substances are (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous (a substance dissolved in water).
Step-by-step explanation:
The symbols used in chemical equations to represent the physical state (phase) of substances are: (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous, which means a substance dissolved in water. When writing a chemical equation, it is essential to indicate the physical state of both the reactants and products to provide clarity on the conditions of the chemical reaction. For instance, if sodium bicarbonate decomposes, we would write the equation as 2 NaHCO₃(s) -> Na₂CO₃(s) + CO₂(g) + H₂O(l), where the symbols (s), (g), and (l) represent solid, gas, and liquid respectively.