When potassium reacts with water, we observe:

When potassium reacts with water, we observe a bright flame and rapid reaction. Potassium is an alkali metal that reacts violently with water to produce potassium hydroxide and hydrogen gas, releasing enough heat to ignite the hydrogen immediately. The characteristic lilac-coloured flame seen during this reaction is due to the excitation of potassium ions by the intense heat of the exothermic process. The reaction is so vigorous that the potassium metal skims across the water's surface, hissing and sparking until it completely dissolves or explodes.