# eli5 how ice is slippery. Is it being a solid with a little bit of water on it?

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eli5 how ice is slippery. Is it being a solid with a little bit of water on it?

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Basically, yes. Friction causes heat, and heat causes a very small amount of the ice to melt. So you get a thin film of water on top of the ice.

There’s an interesting property of ice, which is that water expands when it freezes.

The opposite is also true, then when ice is compressed it causes it to melt.

Therefore when you step on ice, the pressure causes the thin surface layer to melt in response to the pressure of your foot. This makes it incredibly difficult to get any kind of grip on it

All these answers and none correct. The correct answer is we have no freaking clue. The pressure theory is basically debunked by the fact that the pressures needed to do this are insane. The friction melting theory is probably correct but we don’t know. Basically because ice is rough as is everything, friction heats up and creates a thin, molecular scale, line of water between the ice and object on it. Alternatively this doesn’t happen and maybe ice just always has that because of various cohesive forces. The long story short is we don’t know.

You’ll hear that the top layer of ice melts but that’s not quite true. Current theory is that the very tippy top layer of molecules are kinda loose because they don’t have as much holding them in place. So they roll around like a hyper thin layer of marbles.

For people who are older than 5, the molecules are ‘loose’ because when water freezes the molecules from into a hexagonal crystalline structure which is very stable. But the very top layer of molecules don’t have enough molecules around them to form this structure so they aren’t held in place quite as hard. Source: QI.