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(Chem) (Phys) States of Matter: Crystal to Glass Cooling

 
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adedios
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PostPosted: Wed Feb 22, 2006 9:06 pm    Post subject: (Chem) (Phys) States of Matter: Crystal to Glass Cooling Reply with quote






Crystal to glass cooling model developed

TOKYO, Feb. 22 (UPI) -- University of Tokyo scientists have
discovered why cooling sometimes causes liquid molecules to form
disordered glasses, rather than ordered crystals.

Researchers Hiroshi Shintani and Hajime Tanaka have developed a two-
dimensional model of a simple molecular system that can be tuned
continuously from one state to another, including from a crystal to a
plastic crystal to a glass containing crystalline clusters.

The authors take a liquid model whose molecules would naturally form an
ordered crystalline structure and add a potential favoring formation of
disordered clusters of five-fold crystals. The resulting frustration in the
system can then be controlled to alter the degree to which the ordered
structure is formed, against the number of disordered clusters within the
liquid.

They say they are able to show the liquid naturally forms both types of
structure in a dynamic system. The presence of the domains provides a
natural explanation for the dramatic slowing down of the dynamics in a
glassy system.

The research is explained in the March issue of Nature Physics.

*************************************************************

Questions to explore further this topic:

What are the different states of matter?

http://www.chem4kids.com/files/matter_states.html
http://www.idahoptv.org/dialog.....facts.html
http://www.abpischools.org.uk/...../index.asp
http://www.visionlearning.com/.....hp?mid=120
http://www.chem.purdue.edu/gch.....tates.html
http://www.nyu.edu/pages/mathm.....atter.html
http://www.edinformatics.com/m.....matter.htm
http://www.krysstal.com/states.html
http://www.chemheritage.org/ed.....states.htm
http://www.schoolscience.co.uk.....h1pg3.html
http://www.800mainstreet.com/1.....op-of-page
http://www.chembook.co.uk/chap5.htm

States of Matter: A Slide Presentation

http://ull.chemistry.uakron.edu/genobc/Chapter_06/

Animations for different states of matter

http://www.dac.neu.edu/physics.....im0402.htm
http://www.harcourtschool.com/.....of_matter/

What is a solid?

http://www.chem4kids.com/files/matter_solid.html

What is a liquid?

http://www.chem4kids.com/files/matter_liquid.html

What is density?

http://www.regentsearthscience.....solids.pdf

How do solids and liquid compare in terms of density?

http://www.dac.neu.edu/physics.....im0402.htm

Detailed description of solids and liquids

http://www.wpi.edu/Academics/D.....cept7.html

Is glass a liquid or a solid?

http://dwb.unl.edu/Teacher/NSF.....lorin.html
http://math.ucr.edu/home/baez/.....glass.html

What are liquid crystals?

http://www.colorado.edu/physic.....qcrys.html
http://www.lci.kent.edu/lcimages.html

What is a gas?

http://www.chem4kids.com/files/matter_gas.html
http://www.wpi.edu/Academics/D.....cept5.html

What properties do gases have?

http://www.dac.neu.edu/physics.....im0404.htm

What are phase changes?

http://www.bgfl.org/bgfl/custo...../index.htm
http://www.dac.neu.edu/physics.....im0405.htm
http://www.dac.neu.edu/physics.....im0406.htm

What is melting?

http://www.schoolscience.co.uk.....h1pg4.html

What is boiling?

http://www.schoolscience.co.uk.....h1pg5.html

What is evaporation?

http://www.schoolscience.co.uk.....h1pg6.html
What is a phase diagram?

http://wine1.sb.fsu.edu/chm104.....rces06.htm

What is a plasma?

http://www.chem4kids.com/files/matter_plasma.html
http://fusedweb.pppl.gov/CPEP/.....atter.html

What is a Bose-Einstein condensate?

http://www.chem4kids.com/files.....nsate.html

GAMES

http://www.bbc.co.uk/schools/r....._act.shtml
http://www.bbc.co.uk/schools/s.....tate.shtml
http://www.bbc.co.uk/schools/s.....ases.shtml
http://www.bbc.co.uk/schools/s.....uids.shtml
http://nobelprize.org/physics/.....index.html


Last edited by adedios on Sat Jan 27, 2007 3:55 pm; edited 2 times in total
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PostPosted: Mon Oct 09, 2006 3:10 pm    Post subject: Nanocrystals Are Hot Reply with quote

October 9, 2006
Berkeley Lab


Nanocrystals Are Hot
Germanium Nanocrystals Embedded in Glass: They're Hotter Before They Melt and Colder Before They Freeze


BERKELEY, CA — Scientists at the Department of Energy's Lawrence Berkeley National Laboratory have discovered that nanocrystals of germanium embedded in silica glass don't melt until the temperature rises almost 200 degrees Kelvin above the melting temperature of germanium in bulk. What's even more surprising, these melted nanocrystals have to be cooled more than 200 K below the bulk melting point before they resolidify. Such a large and nearly symmetrical "hysteresis" — the divergence of melting and freezing temperatures above and below the bulk melting point — has never before been observed for embedded nanoparticles.

For the full article:

http://www.lbl.gov/Science-Art.....stals.html
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PostPosted: Fri Mar 16, 2007 7:29 am    Post subject: Scientists Make Ice Hotter Than Boiling Water Reply with quote

Scientists Make Ice Hotter Than Boiling Water

By Robert Roy Britt
LiveScience Managing Editor
posted: 15 March 2007
10:18 pm ET

Scientists have turned water into ice in nanoseconds, which means really, really fast. That's not the most interesting part, though. The ice is hotter than boiling water.

The experiment was done at the Sandia National Laboratories' huge Z machine, which generates temperatures hotter than the sun (setting a record here on Earth) and where researchers test what we know about those plain vanilla "phases" in textbooks: solid, liquid and gas.

"The three phases of water as we know them—cold ice, room temperature liquid, and hot vapor—are actually only a small part of water’s repertory of states," said Sandia researcher Daniel Dolan. "Compressing water customarily heats it. But under extreme compression, it is easier for dense water to enter its solid phase [ice] than maintain the more energetic liquid phase [water]."

For the full article:

http://www.livescience.com/for.....r_ice.html
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PostPosted: Sun Apr 15, 2007 1:26 pm    Post subject: Researchers use smallest pipette to reveal freezing 'dance' Reply with quote

DOE/Brookhaven National Laboratory
15 April 2007

Researchers use smallest pipette to reveal freezing 'dance' of nanoscale drops

UPTON, NY – Using what is thought to be the world’s smallest pipette, two researchers at the U.S. Department of Energy’s Brookhaven National Laboratory have shown that tiny droplets of liquid metal freeze much differently than their larger counterparts. This study, focused on droplets just a billionth of a trillionth of a liter in size, is published in the April 15, 2007, online edition of Nature Materials.

“Our findings could advance the understanding of the freezing process, or ‘crystallization,’ in many areas of nature and technology,” said Eli Sutter, a scientist at Brookhaven’s Center for Functional Nanomaterials (CFN) and the lead author of the study.

Melting and crystallization are so-called phase transformations – fundamental processes by which most substances change between a disordered liquid state (such as liquid water) and an ordered solid state (e.g., ice). When a liquid droplet is cooled, the motion of its atoms gradually slows until they come to a stop, resulting in a solid. For large droplets, this crystallization usually starts at a small impurity (e.g., a speck of dirt), from which it rapidly spreads over the entire droplet. However, very pure substances lack such crystallization centers and have difficulty starting the phase transformation.

“The accepted theory of crystallization, developed in the first half of the previous century, predicts that without impurities, a small solid core generated at random in the interior of the droplet initiates the phase transformation,” Sutter said. “Our experiments on very small droplets challenge this theory.”

To study the freezing process at the ultra-small scale, Eli Sutter and fellow researcher Peter Sutter use what is thought to be the world’s smallest pipette, a device capable of producing liquid droplets of a gold and germanium alloy with a volume of only a few zeptoliters (a billionth of a trillionth of a liter). Operated inside an electron microscope, which creates an image of the sample by bombarding it with a beam of electrons, this zeptoliter pipette suspends the tiny droplets so their phase transformations can be studied with high magnification.

To achieve a liquid state, the metallic alloy must be kept at a temperature above 350 degrees Celsius. When the temperature is lowered to about 305 degrees Celsius, the researchers observe a striking phenomenon: The liquid droplets develop surface “facets,” which are straight, planar sections on the otherwise spherical-shaped structures. The facets continually form and decay in an “ethereal dance” of the droplet shape. This “dance” can last for hours, but quickly stops if the temperature is lowered any further. At this point, the droplet solidifies into a structure that is determined by the ending positions of the dancing surface facets.

“In our experiments, solid-like properties first develop in a thin skin at the surface, while the interior remains liquid,” Eli Sutter said.

This finding counters the traditional idea that all crystallization originates in the interior of a liquid droplet, instead showing that the process may differ based on the size of the sample. This work lays the foundation for a better understanding of freezing processes in the environment as well as in nanotechnology. For example, the balance of solid and liquid water in upper-atmosphere clouds – an important factor in climate models – greatly depends on the exact way water droplets freeze. Such parameters might be predicted more accurately with a better picture of the freezing mechanism.


###
This research was funded by the Office of Basic Energy Sciences within the U.S. Department of Energy’s Office of Science. The CFN at Brookhaven Lab is one of five Nanoscale Science Research Centers being constructed at national laboratories by the DOE’s Office of Science to provide the nation with resources unmatched anywhere else in the world for synthesis, processing, fabrication, and analysis at the nanoscale.

One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE's Office of Science by Brookhaven Science Associates, a limited-liability company founded by the Research Foundation of State University of New York on behalf of Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization. Visit Brookhaven Lab's electronic newsroom for links, news archives, graphics, and more:
http://www.bnl.gov/newsroom
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PostPosted: Sat Jun 02, 2007 8:01 am    Post subject: How to Rip and Tear a Fluid Reply with quote

How to Rip and Tear a Fluid
Penn State University

1 June 2007 —In a simple experiment on a mixture of water, surfactant (soap), and an organic salt, two researchers working in the Pritchard Fluid Mechanics Laboratory at Penn State have shown that a rigid object like a knife passes through the mixture at slow speeds as if it were a liquid, but rips it up as if it were a rubbery solid when the knife moves rapidly. The mixture they study shares properties of many everyday materials -- like toothpaste, saliva, blood, and cell cytoplasm -- which do not fall into the standard textbook cases of solid, liquid, or gas. Instead, these "viscoelastic" materials can have the viscous behavior of a fluid or the elastic behavior of a solid, depending on the situation. The results of these experiments, which are published in the current issue of the journal Physical Review Letters and are featured on its cover, provide new insights into how such materials switch over from being solid-like to being liquid-like.

For the full article:

http://www.science.psu.edu/ale.....6-2007.htm
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PostPosted: Thu Jun 21, 2007 7:41 am    Post subject: The smallest piece of ice reveals its true nature Reply with quote

University College London
21 June 2007

The smallest piece of ice reveals its true nature

Collaborative research between scientists in the UK and Germany (published in this week’s Nature Materials) has led to a breakthrough in the understanding of the formation of ice. Dr Angelos Michaelides of the London Centre for Nanotechnology (formerly of the Fritz-Haber Institut der Max-Planck Gesellschaft in Berlin) and Professor Karina Morgenstern of the Leibniz University Hannover have combined experimental observations with theoretical modelling to reveal with unprecedented resolution the structures of the smallest pieces of ice that form on hydrophobic metal surfaces.

The results provide information about the process of ice nucleation at a molecular level and take science a significant step closer to understanding the mysterious process through which ice forms around microscopic dust particles in the upper atmosphere. Because this is the basis of cloud formation, knowing how different particles promote ice formation is crucial for climate change models.

The authors began by cooling down a metallic surface to 5 degrees above absolute zero (around –268 Celsius) at which temperature it was possible to “trap” and obtain images of the smallest possible pieces (hexamers) of ice using a scanning tunnelling microscope (STM). The hexamer – the simplest and most basic “snow flake” – is composed of just six water molecules. Other ice nanoclusters containing seven, eight and nine molecules were also imaged.

On the difficulties of imaging these ice clusters, Prof Morgenstern said: “Scientists have long struggled to resolve single water molecules within ice clusters, because they are so vulnerable to damage induced by electrons – the very thing that creates the image. The high resolution could only be achieved by reducing the current to the smallest value technically possible.”

As well as performing experiments, the team used highly-accurate (‘first principles’) theoretical models to analyse how such a structure could form. Here the theory provided some surprising insights. In ice, water molecules usually bond to each other with equal strength but with the ice nanoclusters the team identified a pattern of alternating shorter and longer bonds between the water molecules. This pattern provided new information about the ability of water molecules to share their hydrogen bonds, revealing a hitherto unknown competition between the ability of water molecules to bind to a metal surface and simultaneously accept hydrogen bonds.

Dr Michaelides said, “We are all familiar with the freezing of water. It features prominently in our daily lives, from fridge freezers to winter snow. Despite all this, the question of how individual water molecules come together and give birth to ice crystals remains mysterious. Our research provides an insight into the most important and ubiquitous type of ice nucleation event, namely heterogeneous nucleation. State-of-the-art experimental and theoretical techniques allowed us to “watch” and accurately model what happens at very low temperatures.”

The research makes it possible to explain the ways in which water structures form on different substrates, such as transition metals and salt surfaces. It may also provide a new way of thinking about the structure of ice clusters that form on solid surfaces in general, opening the door for applications in a variety of fields as diverse as astronomy, electrochemistry, and energy research. It also takes us a step closer to understanding how water interacts with different aerosols and dust particles in the atmosphere, processes which drive cloud formation and have a large impact on the planet’s climate.

###
Notes to editors:

Contact details:

For more information and high-resolution images, please contact Dave Weston at the London Centre for Nanotechnology on tel: +44 (0)20 7679 7678, mobile: +44 (0) 7733 307 596, out of hours +44 (0)7917 271 364, e-mail: d.weston@ucl.ac.uk

Funding:

Work at the Fritz-Haber-Institut der Max-Planck-Gsesllschaft was funded by the Deutschen Forschungsgemeinschaft (DFG) and European Science Foundation through a European Young Investigator Award (EURYI). See www.esf.org/euryi

Work at the London Centre for Nanotechnology was funded by the Engineering and Physical Sciences Research Council (EPSRC) and European Science Foundation through a European Young Investigator Award (EURYI). See www.esf.org/euryi

Work at the Leibniz University of Hannover was funded by the Deutsche Forschungsgemeinschaft (DFG).

About the London Centre for Nanotechnology

The London Centre for Nanotechnology is a joint enterprise between University College London and Imperial College London. In bringing together world-class infrastructure and leading nanotechnology research activities, the Centre aims to attain the critical mass to compete with the best facilities abroad. Furthermore by acting as a bridge between the biomedical, physical, chemical and engineering sciences the Centre will cross the 'chip-to-cell interface' - an essential step if the UK is to remain internationally competitive in biotechnology. Website: www.london-nano.com

About UCL

Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. In the government’s most recent Research Assessment Exercise, 59 UCL departments achieved top ratings of 5* and 5, indicating research quality of international excellence.

UCL is the fourth-ranked UK university in the 2006 league table of the top 500 world universities produced by the Shanghai Jiao Tong University. UCL alumni include Mahatma Gandhi (Laws 1889, Indian political and spiritual leader); Jonathan Dimbleby (Philosophy 1969, writer and television presenter); Junichiro Koizumi (Economics 1969, Prime Minister of Japan); Lord Woolf (Laws 1954, Lord Chief Justice of England & Wales); Alexander Graham Bell (Phonetics 1860s, inventor of the telephone), and members of the band Coldplay.
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PostPosted: Mon Aug 20, 2007 3:24 pm    Post subject: New finding bubbles to surface, challenging old view Reply with quote

August 20, 2007
Purdue University

New finding bubbles to surface, challenging old view

WEST LAFAYETTE, Ind. - Chemical engineers have discovered a fundamental flaw in the conventional view of how liquids form bubbles that grow and turn into vapors, which takes place in everything from industrial processes to fizzing champagne.
The findings cast into doubt some aspects of a theory dating back to the 1920s that attempts to describe the underlying molecular mechanism behind a phenomenon called "homogeneous nucleation," said David S. Corti, an associate professor of chemical engineering at Purdue University.


The research could lead to a more precise understanding of the "phase transition" that takes place when bubbles form, grow and then become a vapor, which could, in turn, have implications for industry and research, Corti said.

In the conventional view, a liquid boiling and turning into a vapor takes place in a systematic process known as "nucleation and growth." The liquid first forms tiny "nuclei," or microscopic bubbles, that eventually grow as they pick up particles like a snowball gaining size as it rolls down a hillside. This conventional view is described by "classical nucleation theory," which was originally proposed in the 1920s.

"Our findings indicate that this is not what's going on," Corti said. "The bubble grows via a mechanism very different from classical nucleation theory."

Findings are detailed in a research paper appearing online this month in the journal Physical Review Letters. The paper was written by Corti and chemical engineering doctoral student Mark Uline.

As water is heated in a pot on a stovetop, it begins boiling when the temperature reaches 100 degrees Celsius, or 212 degrees Fahrenheit.

"You get little microscopic bubbles that form on the surfaces of the pot," Corti said.

This bubble formation on a surface is called heterogeneous nucleation. Bubbles also may form, however, by homogeneous nucleation, in which they appear not on surfaces, but within the liquid itself. The new findings specifically apply to homogeneous nucleation.

"A common example is when you heat water in a microwave oven," Corti said. "It heats liquid from the inside as opposed to on the surface, so you can actually raise the temperature of the water above 100 degrees Celsius and it doesn't boil. Sometimes when you microwave water in a mug you can superheat it and, if you put a spoon in there after removing it from the microwave, you introduce nucleation sites and it boils off and sprays hot water. The transition happens rapidly, causing a vapor explosion."

The conventional nucleation theory uses the same mechanism for how liquid droplets condense from a vapor in attempts to describe how bubbles form in a liquid. The Purdue researchers found, however, that bubbles do not form by the same mechanism as condensing droplets, Corti said.

According to the conventional theory, the pathway going from a liquid to a vapor is narrow, strictly defining the molecular mechanism by which the liquid becomes a vapor.

"You could think of this pathway as a mountain pass," Corti said. "In order to get from the liquid to the vapor, you have to go over this mountain pass. If you climb up and you're not quite at the top, sometimes you can roll back down, but if you get to the top, you can roll down to the other side and get to the vapor phase."

The new research has shown that this metaphorical mountain pass is actually more broad and flat than previously thought, meaning there are several possible pathways responsible for the phase transition.

"At the same time, what we found is that once you get over this mountain pass, which is called the free energy surface of bubble formation, the surface disappears," Corti said. "You look at one side and you see the mountain and think everything is OK, but once you climb over, it's as if the mountain disappears on the other side."

In the conventional view, the forming bubbles moving down the mountain pass could, in principle, reverse direction back toward the liquid phase.

"But in our view, as soon as you get over the top of the mountain, the mountain disappears," Corti said. "You have no choice but to plummet to something else, the vapor phase."

The findings were based on research using new theoretical methods and verified by computational simulations developed by the Purdue engineers.

Nucleation occurs when a liquid is heated above its boiling temperature or when the pressure exerted on a liquid is decreased below the so-called saturation pressure, which is the case when the lid is removed from the bottle of a carbonated beverage such as champagne, beer or a soft drink.

"This also occurs in the chemical industry and in other work environments where liquids flow through pipes, sometimes with undesirable consequences," Corti said. "Depending on the diameter of the pipes, the pressure of the liquid can drop very rapidly, causing it to become superheated, and before the pressure recovers you can get this phase transition."

The bubbles that form can then collapse when the pressure increases again, sometimes causing significant damage to equipment.

In other industrial processes involving propeller blades, bubbles can form or undergo "cavitation" and then suddenly implode, producing high temperatures and extreme pressures and damaging equipment.

"There are tons of examples, but the real fundamental mechanism underlying what's going on is not that well understood, even for very simple systems," Corti said.

New insights into phase transition could translate into practical and safety benefits for industry. Such insights also could result in a better understanding of the mechanisms responsible for initiating "sonochemistry" and "sonoluminescence" processes in which sound waves are used to form tiny bubbles in liquids. As the bubbles collapse, they emit flashes of light and generate high pressures and temperatures that could be used to enhance chemical reactions.

Another potential practical benefit is to improve the manufacture of foams made of plastic polymers that depends on the formation and distribution of bubbles.

Although the new findings indicate current theory does not adequately describe the molecular mechanism for bubble formation and phase transition from a liquid to vapor, the Purdue researchers do not yet know precisely what that mechanism is.

"We are still working out the full implications of this ourselves," Corti said.
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PostPosted: Wed Dec 05, 2007 2:11 pm    Post subject: Major physics breakthrough in understanding supersolidity Reply with quote

University of Alberta
5 December 2007

Major physics breakthrough in understanding supersolidity

University of Alberta physicists take big step forward in understanding possible new state of matter
Physicists at the University of Alberta, in Edmonton, Alberta, Canada, have made a major advance in the understanding of what appears to be a new state of matter.

Working in the highly specialized field of quantum fluids and solids, Prof. John Beamish, chair of the Department of Physics, and PhD student James Day, report their findings in a paper to be published in the science journal Nature on Wednesday, Dec. 6, 2007. Beamish and Day are the only researchers in Canada conducting experimental research in this area of fundamental physics.

At very low temperatures, helium gas turns into a liquid. Put under extreme pressure the liquid turns into a solid. Physicists have been manipulating solid helium so they can study its unusual behaviour.

In 2004, a research team at Penn State university in the United States, led by Dr. Moses Chan, electrified the physics world when it announced that it may have discovered an entirely new state of matter – supersolidity. The team made the discovery by cooling solid helium to an extremely low temperature and oscillating the material at different speeds. They found that the particles behaved in a way not seen before, which suggested it might show the “perpetual flow” seen in superfluids like liquid helium.

Day and Dr. Beamish have taken this research a different direction. In an experiment not done before, they cooled the solid helium and manipulated the material another way – by shearing it elastically. In doing so, they found that the solid behaved in an entirely new and unexpected way – it became much stiffer at the lowest temperatures.

“The experimental results from the University of Alberta are remarkable,” Dr. Chan said. “Namely, Professor Beamish and his student James Day found that the shear modulus of solid helium increases by 20% when it is cooled below 0.25K.

“Furthermore, the temperature dependence of the shear modulus seems to track the period change seen in torsional oscillator. It seems the two phenomena are related and probably have the same mechanical origin.

“This is an important breakthrough since the original discovery,” Chan said.

Other physicists around the world are also studying the implications. Through this discovery, Beamish and Day have significantly added to the body of knowledge about the fundamental states of matter allowed by nature.
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PostPosted: Thu Jan 10, 2008 7:42 pm    Post subject: Inside Look at How Ice Melts Reply with quote

Inside Look at How Ice Melts
By Dave Mosher, LiveScience Staff Writer

posted: 09 January 2008 12:01 am ET

The science of melting ice just became a little more solid.

A new computer simulation shows that frozen water molecules, when heated up, vibrate until they start to spin. The swiveling motion causes the Mickey-Mouse-shaped particles to break free of their ice crystal home, bump into neighboring molecules and start a chain reaction of melting.

For the full article:

http://www.livescience.com/tec.....melts.html
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