1. If you take beer out of the fridge, dip it for 30 seconds in liquid nitrogen, then open it, it will foam up. Skipping the LNO2 cooling stage, it doesn't foam up, why? 2. Pouring a bottle of beer into Dewar of liquid nitrogen, then letting LNO2 evaporate leaves pieces that are shaped like popcorn. Other substances like grain alcohol leave chunks that look like chunks of water ice...why?