Alkali metals (like Potassium and Sodium) react vigorously or even explosively with cold water, producing hydrogen gas and their hydroxides. Calcium, an alkaline earth metal, also reacts with cold water, albeit less vigorously than sodium or potassium, forming calcium hydroxide and hydrogen gas. Magnesium, another alkaline earth metal, reacts very slowly with boiling water and reacts readily with steam to form magnesium oxide and hydrogen, but it does not react with cold water.