Want a new party trick?

And now done with water…

This is called supercooling. When water is pure enough, there’s nothing that the H2O can bind to in order to start the phase change, as the H2O liquid can’t form a crystalline form against other H2O liquid.  A simple gaseous bubble of air is enough though to start the freezing process.

With the beer, when you open the bottle, the concentration of dissolved CO2 changes because the bottle has been opened/depressurized. The loss of pressure causes CO2 that has been forced into the solution to escape (usually forming bubbles along the side of the glass), lowering the concentration and raising the freezing point. The temperature is still low, but the freezing point is much higher, so the liquid.

There are many more videos of supercooled liquids on youtube.

And just because you can get water to stay in liquid form after it’s passed the freezing point doesn’t mean you can’t do the same with the boiling point. You can also superheat water — heat it past the boiling point.

In this vid, the temperature of the water passes the boiling point of water, but there aren’t enough impurities to allow bubbles to form (so the water doesn’t boil). A little agitation lets the bubbles form, and the water violently turns to steam (which carries way more energy than water).

Wikihow has a decent writeup of some methods on how to to supercool water.  Remember kids, always practice safe chemistry standards and only perform experiments under adult supervision.