Physics question involving wine

[Darg]

Okay, to set the scene:

It was a fine summers day, today in fact. The sun was shining, the beaches were packed and barbeques were planned. Wine was procurred, a bottle of white, and taken as gifts to these feasts of meat. Alas the heat was too great and the bottle was warm, into the freezer we said as the charcoal was burned.

Two hours later and several stomachs well stuffed the wine was remembered and rescued with haste. Hurray we all cheered it hasn't frozen yet, just well chilled and ready. What's this on the inside, a small dot of ice. Incredible it seemed that just that was frozen, the bottle was tilted and yes the rest was still liquid.

But wait what is this, the white spot is spreading what can we do all our wine is unmelting! In seconds it was solid just a white lump of ice. What has just happened, how did what was liquid suddenly turn solid when it had already been taken from the freezer??

 

[alex24]

Yeah, it's pretty cool when that happens. You can cool water to below it's freezing point and it won't crystallise until it's seeded. It's called supercooling (superheating is also possible - don't microwave a mug of water without a seed in it for example!) and is basically a kinetic effect whereby a metastable state can be obtained in a compound despite being below the freezing point (i.e. thermodynamically unstable). The actual science of this is a bit more complicated and due to how water must rearrange to form a crystal, but in you moving the wine bottle, it allowed the small seed in the centre to propagate and freeze the entire bottle. Would make a tasty ice lolly!

Thermodynamic instability of compounds is actually more common than most people realise, a classic example being in diamond, which is metastable (thermodynamically unstable) at room temperature and pressure. But diamond rings don't turn into graphite (which is stable) because of the kinetic boundaries to this process - it requires activation energy. Still, you could put your diamond into an oven and in around a week it would be graphite. Obviously not recommended, but it is giving it the required energy to rearrange into the most stable state.

 

[Darg]

Thanks guys that's pretty cool