Why does beer only freeze when you open it?

Beer bottles

Question

I like really cold bottled beer. But when I put it in the freezer, why is it liquid until I take the cap off and then freezes?
Claire, Holloway

Answer

** Definitive **
Name: Daniel, Chiswick
Qualification: Scientist
Answer: Liquid can only freeze as crystals. The crystal needs something to hold on to. In a bottle, the liquid has nothing to seed on. When the cap comes off, it bubbles and the crystals have something to seed on.
Name: David
Qualification: Chemistry at school
Answer: It's due to pressure. When it's in the bottle, it's pressurised. When the cap comes off, that is reduced and it freezes.
Do you know the answer? Let us know in the box below.