Water; required for life (Introduction)

by David Turell , Thursday, December 08, 2016, 00:51 (2907 days ago) @ David Turell

Water has many strange properties still being studied and understood:

http://phys.org/news/2016-12-uncovering-secrets-ice-materials.html

"Water is vital to life on Earth and its importance simply can't be overstated—it's also deeply rooted within our conscience that there's something extremely special about it. Yet, from a scientific point of view, much remains unknown about water and its many solid phases, which display a plethora of unusual properties and so-called anomalies that, while central to water's chemical and biological importance, are often viewed as controversial.

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"Whenever liquid water freezes, only its oxygen atoms actually end up in fixed positions," explained Christoph G. Salzmann, associate professor and Royal Society Research Fellow, Department of Chemistry, University College London. "The hydrogen atoms remain disordered—so we call such phases of ice 'hydrogen disordered.' Upon cooling, the hydrogen atoms are expected to become ordered and result in hydrogen-ordered ices. Yet, this process is difficult because the reorientations of the hydrogen-bonded water molecules are highly cooperative."

"To help explain the concept, he used a tile game as an analogy.
"Moving from disorder to order is difficult work because the tiles can't move independently—similar to the situation in ice," he said.

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"Ice VI and ice XV are both high-pressure phases of ice that form at about 10,000 atmospheres. "The structure of ice XV has been the topic of lively scientific discussion for years," Salzmann said. "A variety of different and, in part, conflicting models have been suggested from both experimental data—including a previous study by our group—as well as computational studies."

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"The group's work represents a major change in the understanding of ice XV that consolidates much of their previous work. "First, we've shown using neutron diffraction at the ISIS Science and Technology Facilities Council in the U.K. that the ice shrinks in two directions, but expands in the third during the transition from ice VI to XV," he explained. "Using density functional theory calculations, we can show that only one particular structural model of ice XV is consistent with these changes."

"Incidentally, this structure is also the one the group proposed from their in-depth analysis of neutron data.

"'This agreement between experiment and calculations is great, in particular, because there have been conflicting views regarding ice XV," he added. "The overall volume of the ice increases during the phase transition, which finally explains why the transition is observed more readily at ambient pressure than at higher pressures—behavior that has puzzled us for a long time."

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"'There's still an open question about why we can't achieve full order in ice XV," Salzmann said. "We've already started new experimental work to explore how the properties of ice change within nanoconfinements and the presence of chemical species—because we're interested in understanding the complex behavior of ice on comets and within our atmosphere.'"

Comment: Water in general has weird properties. When water freezes the ice expands to a larger volume and floats. This helps aquatic animals and plants to stay under it in liquid water and remain protected from the colder environment above the ice. Is this a part of the fine tuning for life. As we understand more about the properties of water on comets we may find more evidence of fine tuning.