If francium was dropped into water, the reaction would be explosive and violent. Scientists expect that francium would dart on the surface of water and produce a hissing sound.
Francium is the most reactive element of the first 101 elements. The element is not available in enough quantities to enable an experiment with water. Hydrogen and francium hydroxide are the expected products of the reaction. Francium is a member of the alkali metals and is very similar in properties to cesium, which explodes in cold water. Scientists use these types of facts to speculate on the reaction francium would have with water.