Remember- We’re in GQ not GD so may I suggest keeping the insults out of the discussion?
IIRC, water begins to expand at 4 degrees above 0 Celsius. I think this is what people have taken to be the “beginning to freeze” part. You could, I think, argue that freezing requires the apropriate distance between the water molecules (under “normal” conditions) and therefore the expansion that occurs before it becomes solid (freezes) is part of the process (necessay for) freezing.
PC
P.S.- GQ is for dispelling ignorance. The Pit is for bashing it.
Imagine an ice cube sitting in a perfectly insulated glass of water at 0C. Will it melt or will the water freeze? neither. More precisely, it is doing both but they are in perfect balance. You have to remove 40 calories of heat (that is .04 of what we usually call calories, which are correctly called kilocalories) from each gram of water at 0C to freeze it and you have to add 40 cal of heat to a gram of ice to thaw it. Both freezing and thawing are actually taking place, but they cance. Now add a bit of heat to this sealed system. Now some ice will thaw. Now remove a bit of heat and some water will freeze. So 0C is the temperature at which ice and water can exist in equilbrium.
Now what happens at 4? Clearly something happens because if you either cool it or heat it, the density rises. I imagine that as you cool it starts to organize itself towards the crystalline structure of ice and if you want to call that, “beginning to freeze” go ahead. But there is no noticeable increase in viscosity or any other obvious physical change that I would use that expression to describe. “Getting slightly denser” would do it for me.
That’s only true for a flat water/ice interface. In fact, the corners of an ice cube are unstable and will melt very slowly at 0C. Also, any fissures in the ice are unstable and will fill in. Over time an ice cube at 0C is trying to turn into a sphere.
I’ve seen this explained in terms of “surface energy.” The molecules on the surface of a solid sphere are more easily dislodged when the sphere is smaller (with a highly curved surface.) The opposite is true of the molecules at the surface of a tiny spherical pocket of liquid water imbedded within ice. Small bits of ice can melt at 0C, while small water-filled pockets within a block of ice will freeze solid at 0C.
I see the above effect all the time: if two ice cubes in your drink are in gentle contact, the fissure between them quickly fills with ice, and their sharp corners become rounded.
