Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Question about fundamental chemistry of water answered

19.02.2004


Water is simple, right? It is a simple, stable molecule - two hydrogen atoms strongly bonded to an oxygen atom. It is common in the universe, existing at a wide range of temperatures. As a liquid, it has interesting properties that allow it to dissolve many substances. It is basic to life, and it makes up most of your body.



However, a vigorous argument about some fundamental physical properties of this ubiquitous substance has been raging for over half a century. Now, a new finding to be published in the February 19 issue of the journal Nature may settle the dispute.

The article, by Y-Z Yue of Aalborg University in Denmark, and C.Austen Angell of the Department of Chemistry and Biochemistry at Arizona State University, is entitled "Clarifying the glass-transition behavior of water by comparison with hyperquenched inorganic glasses."


The authors argue that the currently accepted temperature at which water in the glassy state softens into a liquid ("glass transition"), is incorrect due to mistaking an "experimental artifact" for the glass transition itself. In fact, Yue and Angell argue that the amorphous solid form of water crystallizes before this softening ever happens.

Most of us assume that water’s basic properties are well understood, but in many ways, they are not. While we are familiar with water either as a liquid or as a crystalline solid (ice), its most common state in the universe is as a glass, a peculiar form of matter which is solid like ice but has a disorderly arrangement of molecules like a liquid. Scientists believe that water mainly exists in the glass state in intergalactic space -- in water films on dust particles -- and that comets (sometimes affectionately called "dirty iceballs") are made of it as well.

The transition between a liquid and its crystalline solid phase is sudden, with an abrupt change in the material’s heat content -- and state of order -- occurring when the material changes phase. Glasses, however, show a very different sort of behavior when they are heated, changing into a liquid gradually, showing a jump in heat capacity as the softening begins, but no jump in energy or state of order, as in melting. This jump in heat capacity defines the "glass transition."

Chemists, who form glassy water in the laboratory by splattering micro-droplets on extremely cold surfaces (a process called "hyperquenching"), were long unable to detect a glass transition for glassy water, as the material appeared to change to a crystalline solid before reaching the transition temperature. Finally, in 1987 a weak heat capacity change was thought to have been detected at 136 degrees Kelvin by "annealing" (heating and re-cooling to relax its structure) the water glass before it reached the point where it crystallizes. Since then, this has been generally accepted as the glass transition for water.

Now, Yue and Angell have shown, by examining a number of other hyperquenched inorganic glasses that have known glass transitions, that annealing the glasses causes a "shadow" of the glass transition to occur at lower temperatures than the actual transition occurs at.

"What people thought was the glass transition in water is actually just an annealing effect," said Angell. "The actual glass transition temperature cannot be seen in any experiment because, as many of us thought before, water crystallizes before the glass transition can occur."

Angell’s results point to a new understanding for the phases of water. Glassy water can now be seen as remaining solid (not changing to a liquid) at a much higher temperature than before, probably because of the strong tetrahedral network of hydrogen bonds holding the water molecules in place. However, this network is disrupted when substances dissolve in the water.

This fundamental problem on water has been only one part of a flurry of recent activities in Angell’s lab, including some that have potential importance for new technology. In a paper published in the October 17 issue of Science, Angell announced the development of a class of salts that, without needing a solvent to dissolve them, are liquid at room temperature and have the conductivity of aqueous solutions. These electrolytes not only closed a historical gap between aqueous solutions and other liquids but also prove to be exceptional, possibly superior, electrolytes for use in developing efficient hydrogen fuel cells.

In other, more esoteric, work Angell and colleague Srikanth Sastry, at the Nehru Research Center in India, reported in the November 27 issue of Nature Materials that a liquid-to-liquid phase transition, much discussed but not proven in connection with the anomalies of water, had been clearly observed in the liquid state of silicon. Silicon, in analogy to water, likes to have four nearest neighbors around every atom forming a network like that in glassy water.

James Hathaway | EurekAlert!
Further information:
http://www.asu.edu/asunews/

More articles from Life Sciences:

nachricht What happens in the cell nucleus after fertilization
06.12.2016 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Simple processing technique could cut cost of organic PV and wearable electronics

06.12.2016 | Materials Sciences

3-D printed kidney phantoms aid nuclear medicine dosing calibration

06.12.2016 | Medical Engineering

Robot on demand: Mobile machining of aircraft components with high precision

06.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>