Is it blown or blew?

Blown and blew are different forms of verb to blow, used in different grammatical contexts. Blew is simple past tense, used for completed action in past, as in wind blew yesterday, he blew up balloon, she blew whistle. Blown is past participle, used with auxiliary verbs has, have, had, is, was, etc., as in wind has blown, balloon has been blown up, candle has been blown out. So you say it blew yesterday not it blown yesterday, and it has blown not it has blew. Common confusion arises because both refer to past, but blew is standalone past, blown needs helper verb. For example, correct is he blew his chance, not he blown his chance, and his chance was blown, not was blew. In slang, blown can be adjective meaning surprised, as in mind blown. So choose blew for simple past, blown for perfect tenses and passive voice. Remember blew is past, blown is past participle needing auxiliary.