State symbols — AQA GCSE Chemistry
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State symbols explained
State symbols covers 2 specification points, including In chemical equations, the three states of… and Students should be able to include appropriate….
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Open a point below for its explanation and revision guidance.
In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions.
State symbols record the physical state of each substance in a chemical equation. Solid is (s), liquid is (l), gas is (g) and aqueous, meaning dissolved in water, is (aq). They are written immediately after the chemical formula, for example 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g). State symbols are added after balancing, because changing a formula to show a state must not change the formula itself. They help chemists check that the equation matches the reaction described, such as a gas being produced or a precipitate forming. Aqueous does not mean liquid water: it means a substance dissolved in water, so an ionic compound in solution is shown as (aq) even though the solution is a liquid.
Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification.
State symbols show the physical state of each substance in an equation: (s) solid, (l) liquid, (g) gas, (aq) aqueous (dissolved in water). They are added after each formula, for example 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g). To choose correctly, identify the state under the stated conditions: metals are usually solid; water is liquid; gases include H₂, O₂, CO₂; solutions are aqueous. For ionic equations, only ions and molecules in solution or as gases or solids are shown, with state symbols where required. The skill is assessed by requiring correct symbols in equations for specified reactions, not by memorising a fixed list.
Your focus
- Write the correct state symbol for a solid, liquid, gas or aqueous solution.
- Place state symbols correctly within a balanced chemical equation.
- Distinguish between (l) for pure liquid water and (aq) for a substance dissolved in water.
Show all 6 objectives
- Assign correct state symbols to reactants and products in a given chemical equation.
- Distinguish between (l) and (aq) for water and aqueous solutions.
- Construct balanced equations with state symbols for reactions in the specification.
State symbols exam tips
Marking Points
- Use (s) for solid, (l) for liquid, (g) for gas and (aq) for aqueous solution.
- Place the state symbol immediately after the chemical formula it describes.
- Use (aq) for a substance dissolved in water, not for pure liquid water, which is (l).
- Check that state symbols are consistent with the reaction described, such as a gas product or a precipitate.
- Keep the chemical formula unchanged when adding state symbols.
- Correctly assigns (s), (l), (g) or (aq) to each substance in an equation according to its physical state under the stated conditions.
- Uses (aq) for a substance dissolved in water, including acids and solutions of ionic compounds, rather than (l).
- Applies state symbols consistently to both reactants and products, including in equations with coefficients.
- Recognises that state symbols may be omitted in some contexts but must be included when the question asks for them or when they clarify the reaction.
- Uses state symbols correctly in ionic equations, for example Ag⁺(aq) + Cl⁻(aq) → AgCl(s).
Examiner Tips
- 💡Add state symbols after balancing the equation so the formulae are already correct.
- 💡Check each symbol against the reaction context, especially whether a product is a gas or a precipitate.
- 💡Remember that (aq) means dissolved in water, so it applies to solutions rather than to pure liquids.
- 💡Read the question carefully: if it asks for state symbols, include them for every substance in the equation.
- 💡Check the physical state at room temperature and pressure unless other conditions are given.
- 💡For ionic equations, include state symbols only for the species shown, and ensure they match the full equation.
Common Mistakes
- Writing (aq) for pure water; correct this by using (l) for liquid water and (aq) only for a substance dissolved in water.
- Placing the state symbol before the formula or inside it; correct this by writing it immediately after the formula.
- Changing a subscript while adding a state symbol; correct this by leaving the formula exactly as it was and adding the symbol after it.
- Writing (aq) for liquid water in a reaction where water is not the solvent; the correction is to use (l) for pure liquid water.
- Omitting state symbols entirely when the question requires them; the correction is to add the appropriate symbol after every formula.
- Using (s) for a dissolved ionic compound such as sodium chloride in solution; the correction is to use (aq) because it is dissolved in water.