Gallium beating heart experiment. A sample of gallium metal is placed in a beaker of warm sulfuric acid. The warmth melts the gallium, and the acid reacts with the surface of the metal, forming gallium sulfate. The molecules of gallium sulfate attract each other strongly, forming a skin that keeps the gallium in a round blob. When it is touched by an iron nail, the surface tension is disrupted, and the gallium begins to flow away. This breaks the connection to the nail, allowing the surface tension to draw the gallium back into a round blob, and forcing it to touch the nail again. This has the effect of causing the gallium to pulsate, like a beating heart.