Lithium reacting with water. Footage of a pipette of water being added to the element lithium, resulting in a violent exothermic reaction and flames as the metal ignites. Lithium (Li) is a highly reactive metallic element. It reacts violently with water to produce hydrogen (H2) gas and lithium hydroxide (LiOH). For high-speed footage of the start of the reaction, with only a few drops of water added, see clip K004/1471.