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From what I've read about heat, temperature and conductivity, I understand that the reason water at room temperature feels colder than most other things at the same temperature (like wood, air, cotton) is because of its higher thermal conductivity. That is, it transfers heat quickly from my body to itself, as well as within itself.

(Assuming the thermal conductivity is the only reason why different materials feel colder or warmer), what I don't understand is why metals feel about as cold as water, while their thermal conductivities are 100-to-200 times higher than that of water (Water's is ~0.58 W/mK, the values for metals range from 50 to 400).

I suppose there is more to why materials at identical temperatures suck heat faster; what is it?

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  • $\begingroup$ The effective thermal conductivity of water is greatly enhanced by convection. $\endgroup$ – Rick Jan 13 '15 at 14:03
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The parts of your body that generate heat and that can sense temperature and the loss of heat are insulated from the environment by a layer of dead skin cells. The total thermal conductivity to the environment is the thermal conductivity of the materials that you touch in series with the thermal conductivity of this layer of skin. Since this layer has a rather poor thermal conductivity itself, the sensation of touching different materials with much better thermal conductivity will not differ much. If this skin layer is broken, however, temperature and heat conductivity differences are felt much stronger, usually in a rather painful manner.

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    $\begingroup$ Another effect that might be relevant is that when you dip your finger in water, the liquid conforms exactly to the shape of your finger and makes good thermal contact, while when you touch a solid metal surface you probably don't make such good contact. $\endgroup$ – Nathan Reed Dec 11 '14 at 23:52
  • $\begingroup$ @NathanReed: I would agree with that. Our skin has probably evolved to minimize thermal contact both in terms of its intrinsic heat conduction and in the way it connects mechanically to cold objects... frostbite can lead to nasty, life threatening injuries. $\endgroup$ – CuriousOne Dec 12 '14 at 0:02
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Several things are happening here that may make the sensations of touching metal and touching water similar when they are at room temperature (~ 25 C), although the thermal conductivities are a couple of orders of magnitude different. The sensation of coldness comes from the loss of heat from the part of your body contacting the material. The rate of heat transfer is proportional to both the difference in temperature between materials and the surface area of the transfer interface. Since the delta-T is about the same, the surface area is the significant variable. As Nathan Reed stated, the conforming nature of a liquid significantly (a couple of orders of magnitude?) increases the surface area of the heat transfer interface. This may offset the difference in thermal conductivities.

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  • $\begingroup$ Neat idea. Surface area almost certainly has something to do with it. $\endgroup$ – Brandon Enright Dec 12 '14 at 0:41
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    $\begingroup$ It might indeed have a role. But still, the effect I'm talking about is present even when touching a plastic bottle filled with water (which is slightly warmer than direct contact with water) and touching the metal frame of a bed with the same finger. The metal is still only slightly colder instead of 100 times. As said above, perhaps our sense of cold and hot is not linearly proportional with the conductivities of materials. $\endgroup$ – Esoppant Dec 12 '14 at 0:50
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The specific heat of air is more than the specific heat of oxygen in water. Therefore, the water is colder than air. neglect the specific heat of hydrogen in water as its density is negligible comparing to the oxygen. Specific heat of oxygen is 0.9 J/g/cCelcius, specific heat of air about 1 J/g/c

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protected by Qmechanic Sep 16 '16 at 2:25

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