Why is Ice So Slippery?

[Peter from Sch'dy]

Seems like a simple question, right?

Another perhaps related question..why does ice adhere to all solid non-heated objects?
Best Regards,
Peter

[kirby1923]

'cause ice molecules like to stick to everything especially wings and windshields!

:-)

[Arizona Wayne]

From the google box:
According to the frequently cited — if incorrect — explanation of why ice is slippery under an ice skate, the pressure exerted along the blade lowers the melting temperature of the top layer of ice, the ice melts and the blade glides on a thin layer of water that refreezes to ice as soon as the blade passes.

"People will still say that when you ask them," Dr. Rosenberg said. "Textbooks are full of it."

But the explanation fails, he said, because the pressure-melting effect is small. A 150-pound person standing on ice wearing a pair of ice skates exerts a pressure of only 50 pounds per square inch on the ice. (A typical blade edge, which is not razor sharp, is about one-eighth of an inch wide and about 12 inches long, yielding a surface area of 1.5 square inches each or 3 square inches for two blades.) That amount of pressure lowers the melting temperature only a small amount, from 32 degrees to 31.97 degrees. Yet ice skaters can easily slip and fall at temperatures much colder.

The pressure-melting explanation also fails to explain why someone wearing flat-bottom shoes, with a much greater surface area that exerts even less pressure on the ice, can also slip on ice.

[Arizona Wayne]

That's written by someone who doesn't skate.  Ice skate blades are not straight.  They have quite a bit of rocker, so the length of contact along  the blade is quite short.  They're also ground with a concave cross section so they contact the ice at the edges first.  Racing skates are often not ground concave, but are very thin compared to figure and hockey skates.

1 time the wife & I went onto a steel grated bridge over a river on our CX100 bent over because the road was not straight approaching the bridge, it was kinked, and we had never been on this road before.  We leaned right, the bike immediately laid over on it's right side, and the bike & us slid across the bridge as if it was ice!  The wet grated steel was so slippery we could hardly walk on it and we didn't get hurt   because we just slid `till we stopped!  The bike didn't fair as well as we did since the right jug/head hit the steel and the fin fender broke off, the spark plug broke in half, the head fins broke off too, all of which immediately fell into the river below!     And yet the bike was still running on the left cylinder while laying on it's right side.   2 kids saw our whole ordeal and 1 of them said, "hey mister, you bike is still running."  So I carefully walked over to it and turned the key off. The front brake lever was toast too.  So if you approach a wet steel grated bridge, make sure you approach it in a straight line and be carefull. 

Come to find out many bicycle riders get hurt on that old bridge too.

[oldbike54]

 Wait , why does your tongue stick to an ice cube ? Something ain't right with all this theorising 

 Dusty

[Arizona Wayne]

Wait , why does your tongue stick to an ice cube ? Something ain't right with all this theorising 

 Dusty

That's not true.  If you want your tongue to stick to something cold, it can't be an ice cube because the IC will start to melt from the heat of your tongue.  Your tongue sticks to metal that's cold enough, which doesn't melt. 

[Jim Rich]

It's the whisky you pour over it that makes it slippery.  Duh

[Penderic]

If you let ice sneak up on you, it can kill you!


Dangerous!


White knuckles!


Where'd she go?

[charlie b]

We used to go through this as an exercise in engineering classes.  Along with the idea that hot water freezes faster than warm water when put in a freezer.

The logic goes back to molecular physics.  The surface molecules are not bound as tightly to the 'ice' as the inner molecules.  There is always some vaporization going on depending on external conditions.  So, there is a layer of 'loosely bound' molecules on the surface (water is not a good description).  That would not be enough by itself to make ice slippery.  You also need it to have a 'smooth' surface.  That comes from the underlying material, or, a built up layer of ice.  So, a smooth surface and the resulting low friction makes it slippery.

Another 'experiment' is to put something on the ice and let it sit.  After a while it will be frozen to the ice (including ice skates).  That layer of 'loose' molecules now are 'internal' and will 'freeze'.