When potassium is added to water it creates hydrogen gas and a potassium hydroxide solution. The reaction releases heat and causes the potassium to burn with a purplish-colored flame.
The reaction between potassium and water can be written as 2K + 2H2O -> 2KOH + H2. It is an exothermic reaction. Assuming the reaction takes place in an environment with oxygen, the released hydrogen gas reacts with the oxygen and ignites. The created potassium hydroxide solution is basic, meaning that it has a pH between seven and 14. Potassium is a member of the alkali metals group of the periodic table, which includes such chemicals as sodium, lithium and rubidium. The reaction between the potassium and water occurs relatively quickly when compared with other alkali metals.