Why walking on ice is difficult? Why is ice slippery?

Winter starts, and the air begins to get chilly, making it perfect to veg on the couch, eat a warm meal, and binge-watch on your favorite TV series. However, if you badly need to go out despite the cozy weather, devote extra caution as streets begin to icy. Thus, making you prone to sliding or slipping. But, what is the reason behind slippery ice surfaces? Is it because ice like water is wet, which makes it slippy?

While it may seem basic, there is no specific answer to that question yet. Scientists have quite an agreement that ice is slippery as an extreme layer of water is present on top of the solid ice beneath it. The said water on top of ice tends to be gluier in texture, opposing what we are used to water that is more fluid and free-flowing. Such a description makes it even more perplexing, and different hypotheses exist on why we slip on icy surfaces.

For many years, experts believed that the thin layer of water results from the pressure being applied to the icy surface. For instance, when you skate on ice, the pressure from the blades causes the ice’s outermost layer to melt. Thus, allowing the skate to glide across that thin film of water. The thin sheet would then refreeze and turn to its solid form after the skate passes.

However, the theory was questioned as some scientists claim that pressure must come in massive amounts for that to happen. And, it was soon found out that the pressure from people’s shoes or skates isn’t enough to cause such changes.

With that, they had to look for another culprit. And, this time, it is friction. We know that friction produces heat as two objects slide onto each other, such as heat you feel when you rub your hands together. With that, a more dominant theory states that friction causes the thin liquid sheet on icy surfaces. As boots, shoes, and tires get in contact with ice, it produces heat from friction, causing it to liquefy and produce the thin sheet of water on the surface.

Perhaps, the most prominent theory results from research conducted by French scientists. They used a device enhanced by a tuning fork, the same tool in music, which can detect the forces responsible during ice skating with incredible precision. The equipment is extremely sensitive that it can capture sounds on a nanometric level.

Through the device, researchers were able to find that friction indeed produces a thin sheet of water. It doesn’t end there, though, as they discovered that the water is ultrathin, that it only measures a hundred nanometers to a micron or only one hundredth the width of a human hair strand.

Moreover, the thin sheet of water is not plain water, but has a viscosity like that of an oil, boasting intricate viscous and elastic properties. That suggests that the ice surface never actually transforms into a solid or liquid form, but more a combined state.

Discovering and further experiments on the molecular properties of the thin sheet of water on icy surfaces may lead to solutions on how to reduce the slipperiness of streets and roads. For now, be careful enough to avoid turns and twists, ups and downs due to the slippery ground.