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 A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>