Nav: Home

How does water melt? Layer by layer!

December 12, 2016

Mainz, Dec. 12, 2016 - we all know that water melts at 0°C. However, already 150 years ago the famous physicist Michael Faraday discovered that at the surface of frozen ice, well below 0°C, a thin film of liquid-like water is present. This thin film makes ice slippery and is crucial for the motion of glaciers.

Since Faraday's discovery, the properties of this water-like layer have been the research topic of scientists all over the world, which has entailed considerable controversy: at what temperature does the surface become liquid-like? How does the thickness of the layer dependent on temperature? How does the thickness of the layer increases with temperature? Continuously? Stepwise? Experiments to date have generally shown a very thin layer, which continuously grows in thickness up to 45 nm right below the bulk melting point at 0°C. This also illustrates why it has been so challenging to study this layer of liquid-like water on ice: 45 nm is about 1/1000th part of a human hair and is not discernible by eye.

Scientists of the Max Planck Institute for Polymer Research (MPI-P), in a collaboration with researchers from the Netherlands, the USA and Japan, have succeeded to study the properties of this quasi-liquid layer on ice at the molecular level using advanced surface-specific spectroscopy and computer simulations. The results are published in the latest edition of the scientific journal Proceedings of the National Academy of Science (PNAS).

The team of scientists around Ellen Backus, group leader at MPI-P, investigated how the thin liquid layer is formed on ice, how it grows with increasing temperature, and if it is distinguishable from normal liquid water. These studies required well-defined ice crystal surfaces. Therefore much effort was put into creating ~10 cm large single crystals of ice, which could be cut in such a way that the surface structure was precisely known. To investigate whether the surface was solid or liquid, the team made use of the fact that water molecules in the liquid have a weaker interaction with each other compared to water molecules in ice. Using their interfacial spectroscopy, combined with the controlled heating of the ice crystal, the researchers were able to quantify the change in the interaction between water molecules directly at the interface between ice and air.

The experimental results, combined with the simulations, showed that the first molecular layer at the ice surface has already molten at temperatures as low as -38° C (235 K), the lowest temperature the researchers could experimentally investigate. Increasing the temperature to -16° C (257 K), the second layer becomes liquid. Contrary to popular belief, the surface melting of ice is not a continuous process, but occurs in a discontinuous, layer-by-layer fashion.

"A further important question for us was, whether one could distinguish between the properties of the quasi-liquid layer and those of normal water" says Mischa Bonn, co-author of the paper and director at the MPI-P. And indeed, the quasi-liquid layer at -4° C (269 K) shows a different spectroscopic response than supercooled water at the same temperature; in the quasi-liquid layer, the water molecules seem to interact more strongly than in liquid water.

The results are not only important for a fundamental understanding of ice, but also for climate science, where much research takes place on catalytic reactions on ice surfaces, for which the understanding of the ice surface structure is crucial.
-end-
The Max Planck Institute for Polymer Research (MPI-P) ranks among the top research centers in the field of polymer science worldwide. The focus on so-called soft materials and macro-molecular materials has resulted in the worldwide unique position of the Max Planck Institute for Polymer Research and its research focus. The institute combines all the necessary specialized expertise - from the creative design of new materials, from their synthesis in the lab to their physical characterization as well as the theoretical understanding of polymer characteristics. The institute was founded in 1983. More than 500 international people are working at the MPI-P.

More information under: http://www.mpip-mainz.mpg.de

Publication in „Proceedings of the National Academy of Science (PNAS)

„Experimental and theoretical evidence for bilayer-by- bilayer surface melting of crystalline ice" M. A. Sánchez, T. Kling, T. Ishiyama, M.-J. van Zadel, P. J. Bisson, M. Mezger, M. N. Jochum, J. D. Cyran, W. J. Smit, H. J. Bakker, M. J. Shultz, A. Morita,?D. Donadio, Y. Nagata, M. Bonn, and E. H. G. Backus doi:10.1073/pnas.1612893114

Scientific contact:

Dr. Ellen Backus
Max Planck Institute for Polymer Research
Ackermannweg 10
55128 Mainz, Germany
T49-6131-379536
backus@mpip-mainz.mpg.de

Max Planck Institute for Polymer Research

Related Water Molecules Articles:

Breaking water molecules apart to generate clean fuel: Investigating a promising material
Scientists at the Tokyo Institute of Technology (Tokyo Tech) investigated a material that uses sunlight for splitting water molecules (H2O) to obtain dihydrogen (H2).
Source water key to bacterial water safety in remote Northern Australia
In the wet-dry topics of Australia, drinking water in remote communities is often sourced from groundwater bores.
How two water molecules dance together
Researchers have gained new insights into how water molecules interact.
There are no water molecules between the ions in the selectivity filter of potassium
Do only potassium ions pass through the selectivity filter of a potassium channel, or are there water molecules between the ions?
Our water cycle diagrams give a false sense of water security
Pictures of the earth's water cycle used in education and research throughout the world are in urgent need of updating to show the effects of human interference, according to new analysis by an international team of hydrology experts.
Water management helped by mathematical model of fresh water lenses
In this paper, the homeostasis of water lenses was explained as an intricate interaction of the following physical factors: infiltration to the lens from occasional (sporadic) rains, permanent evaporation from the water table, buoyancy due to a density contrast of the fresh and saline water, and the force of resistance to water motion from the dune sand.
Using water molecules to unlock neurons' secrets
EPFL researchers have developed a method to observe the electrical activity of neurons by analyzing the behavior of surrounding water molecules.
Molecular adlayer produced by dissolving water-insoluble nanographene in water
Even though nanographene is insoluble in water and organic solvents, Kumamoto University and Tokyo Institute of Technology researchers have found a way to dissolve it in water.
Water-worlds are common: Exoplanets may contain vast amounts of water
Scientists have shown that water is likely to be a major component of those exoplanets (planets orbiting other stars) which are between two to four times the size of Earth.
How ions gather water molecules around them
Charged particles in aqueous solutions are always surrounded by a shell of water molecules.
More Water Molecules News and Water Molecules Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Accessing Better Health
Essential health care is a right, not a privilege ... or is it? This hour, TED speakers explore how we can give everyone access to a healthier way of life, despite who you are or where you live. Guests include physician Raj Panjabi, former NYC health commissioner Mary Bassett, researcher Michael Hendryx, and neuroscientist Rachel Wurzman.
Now Playing: Science for the People

#544 Prosperity Without Growth
The societies we live in are organised around growth, objects, and driving forward a constantly expanding economy as benchmarks of success and prosperity. But this growing consumption at all costs is at odds with our understanding of what our planet can support. How do we lower the environmental impact of economic activity? How do we redefine success and prosperity separate from GDP, which politicians and governments have focused on for decades? We speak with ecological economist Tim Jackson, Professor of Sustainable Development at the University of Surrey, Director of the Centre for the Understanding of Sustainable Propserity, and author of...
Now Playing: Radiolab

An Announcement from Radiolab