A piece of sodium metal will float when added to a beaker of water. This is because sodium has a density of about 0.93 to 0.97 g/cm³, which is less than the density of water at roughly 1.00 g/cm³, making it less dense and buoyant enough to float. When sodium comes into contact with water, it reacts vigorously and exothermically, producing hydrogen gas and sodium hydroxide. The bubbles of hydrogen gas generated around the sodium help it stay afloat and even move rapidly on the water surface as the reaction proceeds. Additionally, the heat from the reaction melts the sodium, forming a small molten ball that continues to float on the water.