Česky
Throwing a piece of sodium into water is a dangerous, but popular experiment demonstrating an explosive chemical reaction. Every chemistry teacher knows that during the explosion heat is released when electrons move from the metal to water generating water vapor, hydroxide, and hydrogen which can ignite. Gases generated at the interface between the metal and water should, however, separate the reactants and thus quench the explosion. How is it possible that the explosion can nevertheless take place? Thanks to pictures from an ultrafast camera and molecular simulations researchers from the Institute of Organic Chemistry and Biochemistry found a hitherto unknown primary mechanism of the explosive reaction of alkali metals in water. When the electrons move from the metal to water, the former acquires a large positive charge. Repulsion between these charges leads to a Coulomb explosion with metal spikes shooting into water. This leads to effective mixing of reactants thus enabling the explosion.