Does water stick too but we don’t notice?
In: Chemistry
Short story: a thin layer of water on the surface of the ice melts in contact with your skin, and then freezes in all the little grooves of your skin, “gripping” it and sticking. Have you ever seen two very polished plates or other flat things that are hard to separate once you press them against each other? That’s because they’re both flat and a lot of the surface is in contact with the other one. When the ice freezes it makes a surface that mates with your skin perfectly.
Longer story: it may seem counterintuitive that ice can melt and re-freeze again… is it warm enough to melt or cold enough to stay frozen? The key is that ice can be colder than it needs to be in order to stay frozen, and heat doesn’t transfer through ice instantly.
So when you first touch an ice cube, your warm skin beats the outer layer of ice and it melts. However the ice can transfer heat away better than your blood can warm your finger skin, so before too long that heat that melted the outer layer is absorbed by the rest of the ice cube, allowing that layer to freeze again. The whole ice cube is a little warmer now because of all this, but it’s still frozen.
If the ice cube is warm enough, the environment is warm enough and the part of your body touching it is warm enough, it won’t be cold enough for the ice to re-freeze, and it will simply melt and get wet. This is why if you fish a ice cube out of your drink on a warm day, it won’t stick to your hand like we’re talking about.
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Water doesn’t “stick”, but it exhibits capillary action: it gets “sucked” into little grooves by itself. This is how a paper towel dipped into water can soak it up the towel against gravity.
The real parameter that rules the universe is heat, and heat transfer. Temperature isn’t even “real”. You don’t *feel* cold, you feel heat transfer, specifically heat transferring from you to your surroundings. Likewise, you feel heat transferring to you as warmth.
A key component of how heat moves around is how much heat is present in a thermal mass, and how easy it is for a material to give up heat or receive it.
Water is rather miraculous. It is capable of carrying *a lot* of energy in the form of heat. Skin is likewise miraculous. It is a decent biological heat shield, and does a good job of slowing the heat transfer through it. Humans are still most water, so we still have a decent bit of heat within us, but being as we are warm blooded, we retain heat and control how we release heat very methodically. Skin has the capability to transmit heat relatively slowly, and this is generally a good thing for us.
When you touch an ice cube, the temperature difference between your skin and the ice cube is great. The warmth of your skin immediately moves to the ice, cooling your skin and melting a little bit of the ice. But, as the seconds tick onward, heat from your body tries to heat up your skin again. This take time, because your skin naturally is a decent insulator, and resists how much heat can be passed through your skin to warm it back up.
The ice cube on the other hand, has a layer of cold but liquid water between it and your skin. Water is *really* good at transferring heat, so all the heat your body initially transferred to the ice to melt a bit of it gets transferred deeper into the ice cube. As this happens, heat is leaving the liquid water, and eventually it refreezes next to your skin. When the water was liquid, it could get all cozy with every little ridge or divot in your skin, and when it refreezes solid, it forms a perfect match with your skin and therefore is “stuck” to it. Your skin is also somewhat moist, so some moisture in your skin also cools down and freezes, further “sticking” the ice to your skin. Because your skin sucks at heat transfer, but water is really good at it, your body heat is unable to sustain the energy transfer necessary to keep the portion of the ice cube touching you liquid, and any heat you give the ice cube is unlikely to do anything substantial beyond just melting a tiny bit of water initially.
So, long story short, you end up with ice cubes that “stick” to you .
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