Final answer:
A base is a substance that will dissolve in water to yield hydroxide ions (OH-). Examples of bases include sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)2). These substances dissociate in water to release hydroxide ions.
Step-by-step explanation:
A base is a substance that will dissolve in water to yield hydroxide ions (OH-). The most common bases are ionic compounds composed of alkali or alkaline earth metal cations combined with the hydroxide ion, such as NaOH and Ca(OH)2. These bases, along with other hydroxides that completely dissociate in water, are considered strong bases. For example, when sodium hydroxide (NaOH) is dissolved in water, it dissociates into Na+ and OH- ions.