 If we continue down the column to potassium, we see that the potassium metals also stored under mineral oil to minimize its reaction with the oxygen in the air. If we remove a piece of potassium metal, we can see that the potassium is coated over with a gray coating of the oxide. As we continue down the column, group one metals get softer and softer. The potassium cuts very easily as we cut through the metal we expose the shiny metal surface underneath. The potassium is extremely soft. We can easily flatten out the potassium metal. It has a consistency of cream cheese. The potassium is a metal and is an excellent conductor of electricity. If we add a piece of potassium metal to water, we see that it reacts much more rapidly with the water than the sodium. As you go down the column, the ionization energy decreases and the metal reactivity increases. The reaction is very exothermic and the hydrogen that's produced ignites. We can test for the formation of potassium hydroxide by adding phenothaline. The solution turns red-purpled due to the formation of potassium hydroxide.