Or, why you can glide on skates. Water has a very novel phase diagram in that increased pressure on the solid form of water (ice) can force the substance to melt. (In many substances, the application of pressure would lead to solidification or freezing.) Ice skates concentrate the weight of a skater onto a very small area of metal in contact with the ice surface. Since pressure is the force (here, the weight of the skater) per unit area, the result is relatively high pressure immediately underneath the skate's blade. A thin layer of melted ice (water) forms, and this is what allows a skate to glide on ice. Note that the temperature of the ice/water has not changed. The effect is not due to friction. (If there were friction, you wouldn't glide.)

I now realise that this refers to why does ice float?. But i like this write-up, too.

It is a common misconception that the "slipperiness" of ice is caused by a localized high pressure exerted by an object on the ice. While it is true that ice melts under pressure, this factor by itself cannot explain why skates move so well over ice.

Experiments have shown that in order to lower the melting point of ice by one degree Celsius (1.8 F), approximately 12.2 MPa is required. That is more than 120 times atmospheric pressure; a truly large quantity. An ice skater would only be able to exert about 10% of this pressure. Besides, much lighter objects (think about hockey pucks) glide on ice just as good.

The slipperiness of ice is caused by an effect called Surface Melting. This concept was first postulated by Michael Faraday (1791-1867). Molecules in a solid lattice have a limited degree of freedom to move, since they are surrounded by other molecules. However, molecules at a free (solid/gas) boundary have more freedom, and thus show more disorder. Because of their less restricted freedom, these molecules show liquid like behavior in a quasi-liquid surface layer. Surface Melting can occur at temperatures below the bulk melting point of the solid. Thus, the slipperiness of ice is actually caused by lowering the friction at the solid interface.

Surface Melting of a solid is dependent of temperature. As the temperature is decreased, the quasi-liquid surface layer becomes smaller. Hockey players, Speed skaters and Figure skaters should already know this; from experience, the temperature of the ice floor is very important for optimum performance.

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