Beer Freezing experiment

My chemistry teacher said he’d show this on Friday if I did it, and I have (I am so proud of myself). If you want to try this, put a beer in the freezer for over two hours, take out and tap on a work surface (Don’t smack it too hard, the bottle will shatter and you’ll get hurt). When a sealed beer goes below freezing, tapping it will bring out a crystal around which other crystal can form, causing the beer to freeze!