Cutting sodium metal with a scalpel. The shiny exposed metal surface reacts rapidly with oxygen and water in the air, forming a duller layer of sodium oxide and hydroxide. Then the sodium metal is dropped into water. The reaction produces hydrogen gas and sodium hydroxide. The heat of the reaction melts the sodium, which forms a sphere. The indicator phenolphthalein has been added to the water, which turns pink due to the presence of the strongly alkaline sodium hydroxide.