The surprising science of why ice is so slippery


How ice skating works, according to physics and chemistry.

Winter Olympic ice sports are possible due to this one fact: Ice is slippery.

The low friction of ice is why speedskaters can reach 35 mph, why figure skaters can twirl in dizzying circles, and why a 40-pound curling stone can glide and accomplish whatever the heck the point of curling is.

But for much of the past two centuries, scientists have struggled to explain why, exactly, ice is slippery — and why skates can glide atop it so well.

One obstacle: Skates on ice are surprisingly hard to study. You can’t see what’s happening when a blade is cutting through the ice because the blade obscures the view. And the ice layers that skates glide on are microscopically thin.

So scientists have to rely on their knowledge of physics and chemistry for an explanation. They’ve come up with a few overlapping ones that each elucidate a fascinating property of ice.

First off, a refresher: What is ice?
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Ice is solid water. You know that. But what happens when it becomes a solid makes this substance unusual and fascinating.

For most substances in the universe, the solid phase is denser than the liquid phase. When a material is cooled enough to form solids, its molecules get bonded in tight arrays. But ice is different. When it drops below 32°F, the special hydrogen bonds that link water molecules together force additional space between the water molecules when they freeze.

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On the left, molecules of liquid water are disorganized and dense.
On the right, molecules of ice are orderly and spread out.

The ice used in rinks at the Olympics isn’t all that different from the ice that …read more

Source:: Vox – All

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