Acids react with some metals to form a salt and hydrogen: acid + metal → salt + hydrogen. Magnesium, zinc and iron react with dilute hydrochloric or sulfuric acid, but copper is less reactive and does not. The hydrogen gas can be tested with a lighted splint, which gives a squeak pop. For example, Mg + 2HCl → MgCl2 + H2 and Zn + H2SO4 → ZnSO4 + H2.
Acids also react with carbonates to form a salt, water and carbon dioxide: acid + carbonate → salt + water + carbon dioxide. Bubbles of gas are seen as the carbonate fizzes. The carbon dioxide turns limewater cloudy. For example, CaCO3 + 2HCl → CaCl2 + H2O + CO2.
To predict the salt, take the metal name from the metal or carbonate and the ending from the acid. Hydrochloric acid gives chlorides, sulfuric acid gives sulfates and nitric acid gives nitrates. Then balance the equation so that there are the same numbers of each type of atom on both sides.