One of Over 700 Sites
	with Guide Alan Bruzel, Ph.D. Bio | Contact

Subjects

Acids Bases pH Analytical Chem Ask an Expert Astrochemistry Atomic Structure Biochemistry Chemical Databases Chemical Warfare Chemistry Clip Art Chemistry History Chromatography Computational Chem Convert/Calculate Crystallography Electrochemistry Environmental Chem Fun Sites General Chemistry Graphics Software How Things Work Inorganic Chem K-12 Grade Lessons Organic Chemistry Periodic Tables Physical Chemistry Polymer Chemistry Spectroscopy Stoichiometry Terminology Toxic Chemicals Subject Library  All articles on this topic

More Sites On This Topic

Apply to become a partner for this site.

Surface Melting of Ice

Dateline: 01/31/00

By Alan Bruzel

What Is Surface Melting?

With only air above them, molecules at the surface of solids find themselves in an uncomfortable position. Unlike those molecules buried deeper, surface molecules cannot enter into the regular, structured bonding formations characteristic of solids. They therefore show more disorder and are more liquid-like than their neighbors below. Surface melting is the term used to describe this quasi-liquid layer of surface molecules, which exists even at temperatures lower than the bulk melting point of the solid.

What Is Surface Melting of Ice?

It is the presence of a thin film of liquid water on the surface of ice, a concept first postulated by Michael Faraday (1791-1867). Surface melting of ice explains, for example, the slipperiness of ice (because of the lubricating action of the thin liquid film) and why snow can be packed into a snowball (films of water freeze and hold the snowball together).

Why Ice Is Slippery

Ice melts under pressure, but this does not explain its slipperiness. Pressure-temperature experiments have shown that approximately 12.2 megapascals (120 atmospheres) of pressure lowers the melting point of ice by one degree Celsius (1.8 ^oF). A person wearing ice skates exerts about a tenth of this pressure, and thus only lowers the melting point of ice by about a tenth of a degree Celsius. And how do lightweight objects such as hockey pucks slide on ice if pressure, and pressure alone, causes melting? Clearly, another mechanism – the phenomenon of surface melting and its quasi-liquid layer – must be called upon to explain the slipperiness of ice.

How Does Surface Melting Affect Athletes?

Ice at lower temperature has fewer layers of liquid water molecules on its surface than does ice at higher temperatures. Hockey players and speed skaters prefer a colder ice (-9 ^oC) having fewer layers of liquid water. They perform best at a temperature where the lubricating efficiency of the liquid film is greatest, the frictional drag due to increasing layers of water is lowest, and the ice is hard enough to prevent their skates from digging in too deeply. Figure skaters require a softer ice (-5.5 ^oC) where more layers of water control their landings.

Are There Environmental Implications of Surface Melting?

Ice crystals in polar stratospheric clouds, although at temperatures of about -73 ^oC, may, through surface melting, provide the liquid surfaces on which gaseous molecules of ozone, chlorofluorocarbons, and their reaction products dissolve and interact resulting in the reduction of stratospheric ozone levels.

What the Web Has to Say about:
Surface Melting of Ice

Chlorofluorocarbons and Ozone
An article from this Web site describing the environmental impact of chlorofluorocarbons.

Common Theory of Ice Skating Is All Wet!
Correcting a common misconception. From Kevin Lehmann, Princeton University.

How Do Ice Skates Skate?
Ideas for science fair projects from the International Cryobiology Young Researchers Group.

How Is Ice Skating Possible?
Science news article from Jessen Yu, The Stanford Daily.

Ice Skating
Excerpt from Teaching Introductory Physics by Cliff Swartz. Presented by Bill Beaty's Science Hobbyist.

Somorjai Group
Surface chemistry research from Gabor A. Somorjai, University of California at Berkeley.

Surface of Ice
Studies of ice using atomic force microscopy. From the research group of H.-J. Butt, Universität Mainz.

Theory on Antarctic Ozone Hole Boosted by New Observations Confirming Wet Surface of Ice
Article by Lynn Yarris, Lawrence Berkeley National Laboratory.

Why Is Ice Slippery?
The interface between ice and sports. From the Exploratorium's Science of Hockey.

Previous Articles

Subscribe to The Chemistry Newsletter
Name	Email