AQA · GCSE · Combined Science

Course version: 8464 · Version from Sept 2018

State symbols: Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification.

Q: How do I revise State symbols: Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification. for GCSE?

Read the notes on State symbols: Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification., then test yourself without looking. Answering questions and checking what you missed builds recall faster than re-reading.

Q: Is this State symbols: Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification. guide aligned to the AQA specification?

Yes. This guide is linked to the State symbols: Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification. topic in the AQA GCSE specification.

This skill means adding (s), (l), (g) or (aq) to every formula in equations for the reactions you study.

2 key terms

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

Selects the correct state symbol for each reactant and product from the reaction conditions given.
Writes state symbols after each formula and before any + or → symbol.
Uses (s) for insoluble precipitates formed in solution, such as AgCl(s) or BaSO₄(s).
Uses (aq) for dissolved acids, alkalis and salts, and (l) for pure water or liquid mercury.
Balances the equation and includes state symbols without altering the formulae or coefficients.
Applies state symbols correctly in ionic equations, including spectator ions where required.

Common mistakes and how to put them right

Labelling a precipitate as (aq) because it forms in water.
Put it right: An insoluble solid is (s), so write AgCl(s).
Giving water (aq) in a neutralisation equation.
Put it right: Water is the solvent, so correct it to H₂O(l).
Omitting state symbols from one side of the equation.
Put it right: Apply them to every formula on both sides.

Exam tips

Underline or list the physical state of each substance before writing the equation to reduce errors.
Check that coefficients are balanced first, then add state symbols so the two tasks do not interfere.
For precipitation and ionic equations, decide which product is insoluble and label it (s).

Try the lesson

The start of the State symbols: Students should be able to include appropriate state symbols in chemical equations for the reactions in this specification. lesson, made from checked teaching notes for this specification point.

Have a go first

Which state symbol is used for a solid in a chemical equation?

Tip: press 1 to 4 to choose

Listen

This skill means adding (s), (l), (g) or (aq) to every formula in equations for the reactions you study. Decide the state from the substance and the conditions described. For example, burning magnesium in oxygen gives 2Mg(s) + O₂(g) → 2MgO(s). Neutralisation of hydrochloric acid by sodium hydroxide solution gives HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l). If a product is insoluble and forms a solid in solution, label it (s) as a precipitate, for example AgCl(s). Metals are usually (s) except mercury, which is (l). Gases such as O₂ and CO₂ are (g) unless dissolved, when they are (aq). Water is always (l) in aqueous reactions. Apply symbols consistently to both sides and to ionic equations. A strong answer earns marks for these points. Selects the correct state symbol for each reactant and product from the reaction conditions given. Writes state symbols after each formula and before any + or → symbol. Uses (s) for insoluble precipitates formed in solution, such as AgCl(s) or BaSO₄(s). Uses (aq) for dissolved acids, alkalis and salts, and (l) for pure water or liquid mercury. Exam tip: Underline or list the physical state of each substance before writing the equation to reduce errors.

See it

A flowchart starting from a substance in the equation. The first question asks whether it is an insoluble solid formed in solution; if yes, label it (s) as a precipitate. If no, the next question asks whether it is a dissolved acid, alkali or salt; if yes, label it (aq). If no, the next question asks whether it is pure water or liquid mercury; if yes, label it (l). If no, the next question asks whether it is a gas that is not dissolved; if yes, label it (g). If no, label it (s) as a solid. All five outcomes lead to a final step: apply symbols to every formula on both sides. — A decision sequence for choosing the correct state symbol for each substance in an equation.

Key words

Say what each word means before you turn the card.

State symbols

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Precipitate

Try answering aloud or in your head before turning the card.

See every definition

State symbols: Letters in brackets added to every formula in equations for the reactions you study, showing whether a substance is (s), (l), (g) or (aq).
Precipitate: An insoluble product that forms a solid in solution and is labelled (s).

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