Initial Contact: When potassium comes into contact with water, it reacts rapidly. Potassium is a very reactive metal, and this is due in part to its position on the periodic table (it's one of the alkali metals, which are known for their reactivity).

Production of Hydrogen Gas: The reaction breaks down the water (H₂O) molecules, resulting in the formation of potassium hydroxide (KOH) and hydrogen gas (H₂). The chemical equation for this reaction is:

Heat Generation: This reaction is exothermic, meaning it releases a significant amount of heat. The heat is so intense that the hydrogen gas produced is often ignited, causing a flame. This flame is usually lilac or purple, characteristic of potassium's flame test color.

Rapid Movement: The potassium metal may start to move around rapidly on the surface of the water. This is due to the rapid production of hydrogen gas and heat, which can cause the potassium to skitter across the water surface.

Corrosive Nature: Potassium hydroxide, one of the products, is a strong base and can be corrosive. It is also soluble in water, which results in an alkaline solution.

Safety Precautions: Due to its vigorous nature and the heat produced, this reaction is hazardous and should only be performed with proper safety measures in place, such as wearing safety goggles and gloves, and conducting the reaction in a controlled environment.

This reaction is often demonstrated in chemistry classes to show the reactivity of alkali metals with water, but it's always done with strict safety protocols due to the risk of burns from the heat and the caustic potassium hydroxide formed.