Water; has unusual not explained features (Introduction)

by David Turell , Sunday, June 07, 2020, 20:06 (1421 days ago) @ David Turell

Here are five listed:

http://oceans.nautil.us/feature/568/five-things-we-still-dont-know-about-water?mc_cid=7...

"1. How Many Kinds of Ice Are There?
At latest count, there are 17 different crystalline forms of solid water. However, only one form—Ice Ih—exists commonly on Earth outside of the laboratory. A second crystalline form called Ice Ic is present in very minor amounts in the upper atmosphere, and another 15 forms occur only at very high pressures.

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"The application of pressure to tetrahedral substances, including crystalline ice, elemental carbon, silicon, and phosphorus, can collapse low-density solid forms into a variety of structures of sequentially higher density, presumably until the close-packed limit is reached. This produces the 17 forms of crystalline ice we have observed so far. Are there more to discover?

"2. Are There Two Kinds of Liquid Water?
Several decades ago, Japanese scientists claimed to have observed transitions between two phases of amorphous ice under high pressure. Since we believe that amorphous ice is essentially a frozen snapshot of the corresponding liquid, this observation implied that two types of liquid water must exist: normal, low-density water, and a compact high-density form analogous to high-pressure amorphous ice.

"Subsequent simulations have supported this claim. They investigated water whose temperature was below freezing, but above its “homogeneous nucleation temperature” (the temperature below which liquid water cannot exist). In this so-called “deeply supercooled” region, scientists saw evidence for a phase transition between two liquid forms of water.

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"3. How Does Water Evaporate?
The rate of evaporation of liquid water is one of the principal uncertainties in modern climate modeling. It determines the size distribution of water droplets in clouds, which, in turn, determines how clouds reflect, absorb, and scatter light.

"But the exact mechanism for how water evaporates isn’t completely understood. The evaporation rate is traditionally represented in terms of a rate of collision between molecules, multiplied by a fudge factor called the evaporation coefficient, which varies between zero and one. Experimental determination of this coefficient, spanning several decades, has varied over three orders of magnitude. Theoretical calculations have been hampered by the fact that evaporation is an extremely rare event, requiring prohibitively long and large computer simulations.

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"4. Is the Surface of Liquid Water Acidic or Basic?
There is something remarkable about the mist surrounding Niagara Falls: The individual droplets move as if they are negatively charged. The same is true for most waterfalls. This has long been interpreted as evidence for the accumulation of negative hydroxide (OH-) ions at the droplet surfaces, which would mean that the surfaces are basic—with a pH value greater than the 7 of neutral water. In fact, this thinking has become dogma within the community of colloid scientists.

"The surface of liquid water contains a larger number of broken hydrogen bonds, which produce a rather different chemical environment than that found in the bulk. But recent experiments and calculations suggest that hydrated protons (H+) actually dominate the liquid water surface, producing an acidic (less than 7) pH and a positively charged surface, rather than a basic, negatively charged surface.

"Many important processes in chemistry and biology, like atmospheric aerosol–gas exchanges, enzyme catalysis, and transmembrane proton transport, involve proton exchanges at the water surface, and explicitly depend on the pH at the water’s surface—a quantity which is currently unknown.

"5. Is Nanoconfined Water Different?
Water isn’t always sloshing around in giant oceans. Both in nature and in man-made devices, water is often confined to unimaginably tiny spaces, like reverse micelles, carbon nanotubes, proton exchange membranes, and xerogels (which are highly porous glassy solids).

"Both experiment and calculation seem to indicate that water confined by solid walls to tiny regions of space, whose size is comparable to that of a few hundred molecules, begins to exhibit quantum mechanical effects, including delocalization and quantum coherence. These properties are strikingly different from those of bulk water, and could influence everything from biological cells to geological structures. It could be also be of considerable practical significance, for example in designing more efficient desalinization systems.

"Current results remain somewhat ambiguous, however, and more work in this area remains to be done in order to determine the nature of water under confinement.

Comment: Vital for life with many supportive characteristics. Designed that way?