Acids will react with reactive metals, such as magnesium and zinc, to make a salt and hydrogen:
acid + metal → salt + hydrogen
hydrochloric acid + zinc → zinc chloride + hydrogen
The hydrogen causes bubbling during the reaction, and can be detected using a burning splint which produces a squeaky pop sound.
When acids react with metal oxides, a salt and water are made:
acid + metal oxide → salt + water
nitric acid + magnesium oxide → magnesium nitrate + water
When acids react with carbonates, such as calcium carbonate (found in chalk, limestone and marble), a salt, water and carbon dioxide are made. In general:
acid + metal carbonate → salt + water + carbon dioxide
sulfuric acid + iron → iron sulfate + water + carbon dioxide
The carbon dioxide causes bubbling during the reaction. It can be detected by passing the gas through limewater, which will go cloudy.