How are "passions" present in the play Medea and how or why does Euripides "purify" these passions for the audience?
The passions present in the play are the excessive amounts of emotion- both love and hate. The lesson is that moderation is best in terms of either of these passions, because excessive amounts will bring no benefits. Madea is so "in love" that when he leaves her she goes out of her mind, and plots revenge.
Euripides changed the death of the children, that is commonly said to have been an accident in other versions of the myth, into murder to show the catastrophic outcome of excessive passion.