Three crystallizing dishes are half-filled with water and covered with glass plates. Drop lithium metal into the 1 st crystallizing dish and replace the plate. Repeat using sodium and potassium metal. Bubbles form off the lithium because of its reactivity. A stream of smokelike bubbles comes off of the sodium as it changes the water's color.
Potassium explodes in a furious reaction.
The gas observed in each circumstance is the hydrogen produced when the metal hydroxide is formed. The potassium produces this gas the fastest because of its highest reactivity, hence the violent explosion. This is why lithium does little more than bubble and sodium spins quickly in a cloud of gas. The gases produced in these reactions may catch fire because, in all cases, it is hydrogen gas. To furthur reduce the risks associated with this experiment, demonstrators may wish to cover most, but not all, of each crystallizing dish with a watchglass.