Does beer have a lower freezing temperature than water?

Dave - Yes. Beer's got lots of things dissolved in it - alcohol, sugar etc. Anything dissolved in water will reduce its freezing point. So beer does freeze below zero, maybe at -1 or -2.

Chris - And CO2, I suppose, if it's fizzy - that will have an effect too?

Dave - That will also have an effect, definitely.

Chris - So if you were to take some beer and put that in the freezer, could you make it much stronger? Is this a way that you could illicitly do a bit of distillation, because you would freeze the water into ice first, and then some slightly more alcoholic liquid will be left?

Dave - That's right. When you freeze water it can't take in all these solutes, the dissolved things, into it's structure, because ice remains really quite pure. What's left gets stronger and stronger. I don't know if you've ever drunk frozen squash or frozen fruit juice? The stuff you drink first, which is the liquid which melts first, is incredibly strong and very sugary, and then slowly as it melts it gets weaker and weaker, until what's left is basically pure water.