Quote (Thor123422 @ Aug 12 2020 01:45am)
A phase transition is a kind of chemical reaction
H2O (liquid) -> H2O (solid)
When you do a chemical reaction you need an energy to do it, that is there's a barrier of high energy that needs to be overcome. If there wasn't the reaction would have already happened.
When your water is sitting there in the freezer with no disturbances there's no "push" to get over that barrier, but when you poke it, or take the top off, or whatever, it creates a little jostle that results in the activation energy being overcome and the reaction happens.
Now, when water freezes, it releases energy. We know this because if you start taking energy out the temperature will stay constant until all the water freezes. Since water freezing releases energy, when you poke it the energy released from that section freezing then gives adjacent water the energy to overcome the barrier and freeze as well, and continue the process throughout the entire liquid. Additionally, the surface of the newly formed ice creates a "low energy barrier zone", because it takes less energy to add to an ice crystal than to start a new one, so that also allows a chain reaction and freezing to happen.
This is the basics, there's a lot more that can go into it if you want to get a Ph.D in chemical physics, but until then this is all the explanation you need for the basics.
hm okay i get that. i think
but what if i dont give it that initial energy? like, chill it to absolute zero but without shaking the bottle? would it freeze then, and why
? also if yes (and i know its yes, i just dont know why), whats the minimal temperature that i can chill it to, without it randomly turning to ice?
also if the water needs initial energy to start the reaction, why doesnt the heat of my hand holding it start the reaction
?
my head