Why is Ice So Slippery?

[SmithSwede]

Seems like a simple question, right?

[oldbike54]

 Aren't you the MIT grad ? 

 Dusty

[Nic in Western NYS]

I'll bite - it isn't slippery in a solid state, it's the thin water layer that somehow forms on top under pressure that makes it slippery.  Why that liquid layer of H2O forms is not totally 'clear' - get it?  : )

[Wayne Orwig]

What Nic said. It is that perfect, thin layer or water that forms from the friction.

[ridingron]

What Nic said. It is that perfect, thin layer of water that forms from the friction. 

I think it's from the friction and weight. The closer the ice is to the freezing point the more water is melting. Same for snow. That's why you need different wax for different temps. when skiing. Also, different length blades when speed skating. That is of course for the serious skaters.

[oldbike54]

I think it's from the friction and weight. The closer the ice is to the freezing point the more water is melting. Same for snow. That's why you need different wax for different temps. when skiing. Also, different length blades when speed skating. That is of course for the serious skaters.

 OO OO , what would you call a skating club made up of Guzzi riders ?

 Dusty

[twowings]

THIS is why:

https://www.youtube.com/watch?v=ZBrALhb8uiQ

[fotoguzzi]

 I use Crampons when walking the dog these days, wiped out too many times on ice under snow cover.

my son the Hockey player plagiarized this,

A century and a half of scientific inquiry has yet to solve this one. It's clear that a thin layer of liquid water on top of solid ice causes the slipperiness. A fluid's mobility makes it difficult to walk on, even if the layer is thin. But there's no consensus as to why ice�unlike most other solids�has such a layer.

Scientists long reasoned that, since water has the unusual property of being less dense as a solid than as a liquid, its melting point can be lowered with an increase in pressure. While this is true, even the sharpest of skates raises the melting point by only a few degrees. The pressure theory doesn't hold water unless the ice is pretty warm already. Something else must be going on.

Some studies suggest that friction from a moving shoe, skate or tire causes the heat necessary to melt the ice beneath it. But what if the shoe isn't moving at all? A second theory proposes that ice inherently has a fluid layer, caused by the motion of surface molecules that have nothing above to bind to and so move around in search of stability. The slippery culprit may be a combination of these two theories.

[twowings]

The Word of the Day is... ZAMBONI!!!

[sib]

As a corollary to ice being less dense than liquid water (it floats), it has a lower melting point when under pressure.  When compressed (by an ice skate blade, for example), a thin layer of ice instantly melts.  It's actually a thin layer of water you're skating on, even at temperatures well below freezing.

[wirespokes]

Water is weird stuff! A riding buddy used to be a science teacher. He described the anomalies once, but it was confusing enough I don't recall the whole story. I'll have to get him to go through it again. But what I remember was that ice doesn't necessarily float right off - it will stay submerged until the water around it gets to a certain temp. I've since noticed that ice cubes don't always come to the surface when I pour cold juice into the glass. They'll stay on the bottom for several minutes sometimes.

That's interesting data that pressure can instantly melt ice. I never knew that. Have to see what my friend has to say about that!

[ITSec]

Life on earth exists in part because water is more dense than ice. It is one of the four unique things about our planet. The others? We have an extremely large and relatively close moon, leading to substantial tides; we have an atmosphere that is neither too thin nor too dense; and we have a world that constantly rotates at just the right speed.

The combination of cold water sinking (but frozen water rising) and substantial tides means our oceans and larger bodies of fresh water are constantly turning over. This brings nutrients to the surface instead of allowing them to lay on the bottom with no oxygen or sunlight to break them down into useful components. Even further, the movement of the water gets accelerated by the rotation of the earth, creating huge currents. Finally, add in the floating ice at the poles (which conveniently reflects a substantial amount of light) and we have an extension of the warm and cold currents in the ocean into the thinner 'ocean' of air, carrying currents of heat, cold and moisture across the continents.

Eventually, this all leads to the ideal conditions for the rise of life, and the eventual and inevitable creation of Moto Guzzis and roads on which to ride them (Moto Guzzi content!).

[rodekyll]

OO OO , what would you call a skating club made up of Guzzi riders ?

 Dusty

Impossible?   

[oldbike54]

Impossible?

 Not what we were looking for , but a good answer none the less 

 Dusty

[fotoguzzi]

OO OO , what would you call a skating club made up of Guzzi riders ?

 Dusty

the Moto Guzzi Hockey team? A Curling club might be more appropriate ?

[Triple Jim]

When compressed (by an ice skate blade, for example), a thin layer of ice instantly melts.  It's actually a thin layer of water you're skating on, even at temperatures well below freezing.

Right.  It takes a lot of pressure to get the melting point to go substantially lower than 32F to allow skating to work, but there's a lot of pressure under a skate blade, like thousands of PSI.  A good demonstration is to take a cinder block sized block of ice and suspend a heavy weight from it, using a thin piece of music wire looped around it.  If you do it right, the wire will cut all the way through the ice, but the block will remain solid and unbroken, because the ice melts, and the water flows around the wire and refreezes.

If it's cold enough, ice skating stops being possible.  I've never seen it in person, but I've read that it happens around -20F.

[wirespokes]

I'm thinking that with a block of ice suspended by a loop of wire, the wire will gradually work its way through the block with the cut sealing itself back up, so that when the wire finally emerges from the top side, the block will fall (not in two pieces) and smash whatever is below it. This could provide the basis of a murder mystery!

[johnr]

What Nic said. It is that perfect, thin layer or water that forms from the friction.

and/or pressure. (or other sources of heat.)

[RANDM]

Impossible?

 Not what we were looking for , but a good answer none the less 

 Dusty

"The Wholly Rolly Pollies"?  "The Skidmark Skaters"? 

[sturgeon]

OO OO , what would you call a skating club made up of Guzzi riders ?

 Dusty

Toronto Maple Leafs

[rodekyll]

Toronto Maple Leafs

  Brutal!

To answer the OP:  It's not that ice is or isn't slippery, it's that gravity sucks.

[acogoff]

     Our team would be called the "Wild". To avoid a law suit we would have to change it to "just plain goofy".

[oldbike54]

 The correct answer of course is Cheapskates 

 Dusty

[vstevens]

An important part of being slippery includes inertia.  The only reason anything 'slips' on a low friction surface is inertia, Newton's first law or Galileo's law of inertia, which is that any object with mass that is in motion remains in motion until acted upon by an imbalanced force.  And an object at rest remains at rest until acted upon by an imbalanced force. 

Without friction or some other force, you would slide eternally... just like in space.  You would not slow down, speed up, or change direction unless some force acted on you. 


That's why we slide on ice or other low friction surfaces.

Interestingly, Newton's third law states that all forces come in pairs... no such thing as a single, lone force in the universe.  They all come in pairs.
 

[Sasquatch Jim]

 The simplest correct answer it that it is slippery because it is lubricated.

[Two Checks]

Ladies and gentlemen, take my advice. Pull down your pants and slide on the ice.

[acogoff]

The correct answer of course is Cheapskates 

 Dusty

That pretty much hits the nail right on the head, Dusty. A more "tightwadly" (not really a word but fits) bunch I have yet to meet. Myself included.
   As far as ice slipperiness goes a career of government studies could be had just examining the degrees of slipperiness because of snow content, ambient temperature etc. Best not to give those fools ideas to start, Oh wait the DOT has rooms full of these "experts" already doing just that.

[Darren Williams]

The correct answer of course is Cheapskates 

 Dusty

I was thinking "Geezers on Ice".

[Rough Edge racing]

 Yup, it's like why does a skidding tire out run a rolling tire...Spin the tires while moving on ice with a limited slip differential and the ass end comes around...

[Chuck in Indiana]

The correct answer of course is Cheapskates 

 Dusty

<rimshot>