In what way and in what form does potassium react with water?
Potassium reacts rapidly and intensely with water, forming a colourless basic potassium hydroxide solution and hydrogen gas, according to the following reaction mechanism:
2K (s) + 2H2O (l) -> 2KOH (aq) + H2 (g)
This is an exothermal reaction and potassium is heated to such an extend that it burns a purple flame. Additionally, hydrogen released during the reaction strongly reacts with oxygen and ignites. Potassium reacts with water more slowly than does rubidium, which is placed under potassium in the periodic chart. It reacts with water more rapidly than does sodium, which is placed higher in the periodic chart.