Actually, the ending -ão is not telling you anything about the gender of those words. As you exemplified some of them are masculine and some feminine. Unfortunately you'll need to know each one of them by heart until it's natural for you to distinguish the gender of these words. Sorry i couldn't help more.

As palavras coração e paixão são substantivos comuns. A regra da qual você se refere é utilizada somente quando estamos falando de adjetivos, como por exemplo profissões: Ex: Artesão / Artesã, Campeão / Campeã. The words heart and passion are common nouns. We normally apply the rule to describe gender when the word is an adjective that describes some qualification or profission. Ex: Artesão / Artesã, Campeão / Campeã.