Why Do My Ice Skates Slide over the Ice so Easily?
When you ice-skate, you are not skating on the ice itself, but on a slippery film of water between the ice and the skates. When the blade of your skate touches the ice, the heat created by the pressure of your weight melts some ice beneath the blade.
The thin layer of water offers very little friction, and the skate slides easily over the ice. The water quickly freezes again behind you so you hardly notice it when it is melted. An icy sidewalk is slippery for the same reason. The ice melts for an instant under the pressure of your weight and becomes wet and slick.
Unfortunately, scientists later discovered that the pressure applied by skates or people’s shoes standing on ice was not great enough to cause these changes. So, they had to look for another explanation.
In recent years, two other theories have been developed to explain the presence of the thin liquid water layer that exists on ice. One of these theories is that friction causes the liquid layer of water to form on ice. Friction is the force that generates heat whenever two objects rub or slide against each other.
When a skate moves over the surface of ice, the friction between the skate and the ice generates heat that melts the outermost layer of ice. But ice is still slippery even when you’re standing still. If you stand on ice without moving, no friction exists to generate heat, yet the ice is still slippery. So there must be something else going on.
The other theory is that ice is just slippery, because the outermost layer never turns to a solid. According to this theory, the water molecules at the surface of the ice move more, because they’re at the edge and there aren’t any molecules above them to help keep them in place.
As a result, the outermost layer stays in a liquid state even at temperatures way below freezing. So far, scientists haven’t been able to decide which of these two theories is correct. Without a definitive answer at this point, it’s safe to say that both theories play a role in keeping ice slippery.