There is an amazingly clever vaccine cooler (“Sure Chill”), in use in 3rd world countries, that depends on the fact that ice water cools to 4 degrees C, then sinks away from the ice. So, in practice, the ice water is 4C, not 0C.
[tangent]What I find particularly amazing is that this well-known physical phenomena was only recognized as a method for temperature regulation a few years ago (2005). I’m used to semi-conductor physics and medical science, where new developments come from new insights and expensive modern technology, not from noticing something simple that everybody has known forever.
(Apart from the Pfizer vaccine), most vaccines have to be not frozen, so, when used with an ice box, you have to wrap the ice to keep it out of contact. And ice boxes don’t have any way of regulating temperature. Refrigerators depend on electricity (or fuel gas), are heavy and expensive and need complex maintenance. When the power goes off, a typical refrigerator goes off.
By using water density to drive a thermo-syphon, the “Sure Chill” vaccine cooler self-regulates the vaccine chamber to 2-8C, without any mechanical or electric parts, and you can use ice that you make when the power comes on, even if that is only for a couple of hours a day, or back at base.
[/tangent]
That link actually contradicts the OP’s claim that “if you put the vessel with ice water on a stove and heat it, the temperature of the water will[…]remain at that level as long as there is still ice left in it.” The link says, “If you heat a a large pan full of water that contains a single ice cube, the water far from the ice will begin to heat up…”
Only if you consider the whole bucket to be a monolithic “black box” system, which it is not. If you have a 1kg block of ice 2 degrees below the freezing point in a bucket of 1 kg of water at 22 degrees above the freezing point, it makes no sense to say that you have a bucket of ice water that is at 10 degrees above the freezing point. Suppose it’s a block of dry ice instead of water ice. You do not have a bucket of water that is at -80°F. Let’s say you have a bucket with a block of dry ice and a block of wood at 72°F. Do you now have a bucket whose contents is at -18.5°? No. You have a bucket with two materials at different temperatures.
Yes of course. I probably didn’t make my point very well.
The issue raised by the OP was explicitly talking about “the temperature” of a non-equilibrium non-homogenous system. But the OP and at least some of the answers weren’t explicitly aknowledging this.
My point was just that asking about “the temperature” of a non-equilibrium non-homogenous system is nonsense before we begin.
Or to put it another way, any time it’s meaningful to talk about “the temperature” of icewater, it’s always going to be 0 ºC. But it won’t always be meaningful to talk about “the temperature”.
I think it’s fun that a poster named @CookingWithGas is discussing the situation of a pot of icewater being cooked on a stove. Talk about working a problem right in your wheelhouse!
It’s meaningful to talk about “the temperature” of runoff as 0 ºC, but there are other situations where “the temperature of the icewater” is a meaningful number, as in my post above.
Indeed. In fact it is fairly easy to achieve a supercooled state of liquid water that is well below 0 ºC. Anyone who has opened a bottled water from a particularly cold refrigerator and had it turn into icy slush in an instant has demonstrated supercooling.
And to be a bit pedantic, at sea level the triple point temperature of water is not precisely 0 ºC.
@Melbourne, in the situation you describe, the water next to the ice is at 0ºC, but the water at the bottom of the container is at 4ºC, and so there is no one “temperature of the icewater”.
