"The Enduring Mystery of How Water Freezes"

Isaac Asimov was intrigued as all-get-out by water. More after the jump.

From Quanta magazine, June 17:

Making ice requires more than subzero temperatures. The unpredictable process takes microscopic scaffolding, random jiggling and often a little bit of bacteria.

We learn in grade school that water freezes at zero degrees Celsius, but that’s seldom true. In clouds, scientists have found supercooled water droplets as chilly as minus 40 C, and in a lab in 2014, they cooled water to a staggering minus 46 C before it froze. You can supercool water at home: Throw a bottle of distilled water in your freezer, and it’s unlikely to crystallize until you shake it.

Freezing usually doesn’t happen right at zero degrees for much the same reason that backyard wood piles don’t spontaneously combust. To get started, fire needs a spark. And ice needs a nucleus — a seed of ice around which more and more water molecules arrange themselves into a crystal structure.

The formation of these seeds is called ice nucleation. Nucleation is so slow for pure water at zero degrees that it might as well not happen at all. But in nature, impurities provide surfaces for nucleation, and these impurities can drastically change how quickly and at what temperature ice forms.

For a process that’s anything but exotic, ice nucleation remains surprisingly mysterious. Chemists can’t reliably predict the effect of a given impurity or surface, let alone design one to hinder or promote ice formation. But they’re chipping away at the problem. They’re building computer models that can accurately simulate water’s behavior, and they’re looking to nature for clues — proteins made by bacteria and fungi are the best ice makers scientists know of.

Understanding how ice forms is more than an academic exercise. Motes of material create ice seeds in clouds, which lead to most of the precipitation that falls to Earth as snow and rain. Several dry Western states use ice-nucleating materials to promote precipitation, and U.S. government agencies including the National Oceanic and Atmospheric Administration and the Air Force have experimented with ice nucleation for drought relief or as a war tactic. (Perhaps snowstorms could waylay the enemy.) And in some countries, hail-fighting planes dust clouds with silver iodide, a substance that helps small droplets to freeze, hindering the growth of large hailstones.

But there’s still much to learn. “Everyone agrees that ice forms,” said Valeria Molinero, a physical chemist at the University of Utah who builds computer simulations of water. “After that, there are questions.”

Freezing Water
What’s special about zero degrees is that, at or below this temperature, it makes energetic sense for water to turn from liquid into ice. Below that threshold, ice’s crystal structure has a lower energy than sloshing water molecules. The process of freezing water actually releases heat, which is why you can use an infrared camera to see ice heat up as it solidifies....

....MUCH MORE

Isaac Asimov made appearances in a few posts. Here are two from 2020-21:  

"Why Wall Street investors’ trading California water futures is nothing to fear – and unlikely to work anyway"

I don't know. Anything that normalizes the commodification of water, that, rather than exalting it as a giver of life (and one of the weirdest compounds in the universe) reduces it to just another thing to trade, brings us closer to the day when pure power politics forces the U.S. to drain the Great Lakes just to keep Phoenix and Las Vegas and Los Angeles going.

Or something....

*****

...Of course Issac Asimov had to go and pop my quasi-mystical water balloon. In one of Asimov's riffs on water, "Not as We Know it: The Chemistry of Life" he uses this little paragraph as a jumping-off point:

Water is an amazing substance with a whole set of unusual properties which are ideal for life-as-we-know-it. So well fitted for life is it, in fact, that some people have seen in the nature of water a sure sign of Divine providence. This, however, is a false argument, since life has evolved to fit the watery medium in which it developed. Life fits water, rather than the reverse.

From our December 2020 post "Hydrogen Storage: A New Form Of Ice":

The science fiction writer Isaac Asimov was also a trained chemist: PhD, Columbia, post doc, taught biochem at Boston Uni's Med school etc.

And he was fascinated by water. See after the jump.....

Related:
Water and Its Mysterie