Cambridge O Level Chemistry · Syllabus 5070 · Stoichiometry
State symbol
What is State symbol?
A state symbol is the letter written in brackets after a formula in an equation to record the physical state of that species under the reaction conditions: (s) solid, (l) liquid, (g) gas and (aq) dissolved in water.
This definition is part of the Stoichiometry chapter in Cambridge O Level Chemistry.
Questions students ask about State symbol
How do you balance a chemical equation without changing the formulae?
Change only the coefficients, the large numbers written in front of a formula, because they count how many of that substance react. Never change a subscript: the small number inside a formula is part of the substance's identity, so turning \(\mathrm{H_2O}\) into \(\mathrm{H_2O_2}\) balances the oxygen but changes water into hydrogen peroxide. Write the correct formulae first, add state symbols second, adjust coefficients last, then count every element on both sides before you write the answer down.