A salt is formed (with water) when an acid reacts with a base. There are three routes: neutralisation, acid plus metal (gives hydrogen), and acid plus carbonate (gives CO₂). Salts are neutral (strong acid + strong base), acidic (strong acid + weak base) or basic (weak acid + strong base).
Three word equations:
acid + base → salt + water;
acid + metal → salt + hydrogen;
acid + carbonate → salt + water + carbon dioxide.
Naming salts: the first part comes from the metal or base and the second from the acid (hydrochloric acid gives chlorides, sulphuric acid gives sulphates, nitric acid gives nitrates).
Examples: sodium chloride (NaCl), copper sulphate (CuSO₄), potassium carbonate (K₂CO₃), ammonium nitrate (NH₄NO₃), calcium carbonate (CaCO₃), sodium hydrogen carbonate (NaHCO₃).
Gas tests in the experiments: hydrogen gives a 'pop' with a lighted splint; carbon dioxide turns limewater milky.
Uses: salts season and preserve food, treat water, support industry and textiles, feed crops as fertiliser, de-ice roads and go into personal-care products.
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