When a metal or metal salt is burned, the input of thermal energy raises the electrons in the metal atom to a higher energy state. These electrons cannot remain in this excited state for too long and will emit energy in the form of light to return to the more stable, grounded state. It is this light we see when a metal atom is burned in a flame. Each metal has a characteristic flame colour which has been found to be useful in identifying minerals.
Materials: wood splints, Bunsen burner or BBQ lighter, solutions of strontium chloride (red), cupper (II) chloride (blue), copper (II) sulphate (green), calcium chloride (orange), potassium chloride (purple), and sodium carbonate (yellow).