Cesium (Cs) is the most active metal that is available to us in bulk amounts, since francium is too rare and unstable. Cesium is stored sealed in a glass ampoule, most likely under vacuum.
This experiment demonstrates the reaction of cesium with water. As it involves a sizeable amount of a dangerous alkali metal, the experiment was carried out on a former military training ground, using special equipment normally used by bomb squads for transportation.
Detonating cord was attached on the cesium ampoule with duct tape and the ampoule was carefully placed into water bath. Using the electric detonator, the glass ampoule was broken. Cesium and water reacted with a large bang, fireworks and water eruption. The plastic reaction vessel was also smashed.
The products of the reaction of cesium and water are cesium hydroxide (CsOH) and hydrogen:
2Cs(s) + 2H2O(l) → 2CsOH(aq) + H2(g)
or in ionic form:
2Cs(s) + 2H2O(l) → 2Cs+(aq) + 2OH–(aq) + H2(g)
Self-combustion of cesium in air, formation of cesium hyperoxide (CsO2):
Cs(s) + O2(g) → CsO2(s)