The addition of water to aldehydes and ketones is known as hydration and typically results in the formation of a hydrate, which is a geminal diol. In this reaction, water acts as a nucleophile and adds to the carbonyl carbon. The oxygen of the carbonyl group then picks up a proton from water, leading to a 1,1-diol. This reaction is reversible and often favors the aldehyde or ketone in most cases, except when the reaction is catalyzed under acidic or basic conditions or involves highly electrophilic carbonyl compounds.