Learn about chemical tests: identify gases like hydrogen, oxygen, and carbon dioxide using specific reactions. Flame tests reveal metal ions by color, while tests with sodium hydroxide identify cations like Cu²⁺ and Fe³⁺. Anions like chlorides, sulphates, and carbonates form distinctive precipitates when reacted with specific reagents. Water can be tested chemically with anhydrous copper sulphate or physically by its melting and boiling points.