# How can some substances (water, for example) act in some reactions as an acid and in other reactions as a base?

## I don't need the name. I just want to know why because google wasn't very helpful

Water can donate a hydrogen ion and form hydroxide $O {H}^{-}$, making it an acid. It can also receive a hydrogen ion and form hydronium ${H}_{3} {O}^{+}$, making it a base. Hope this helps.