# Why Metal Objects Feel Colder Than Wood Ones? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [November 7, 2002, 11:08pm UTC](https://boards.straightdope.com/t/why-metal-objects-feel-colder-than-wood-ones/135794 "2002-11-07T23:08:41Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Heat\_Transfer\_Guy](https://avatars.discourse-cdn.com/v4/letter/h/d6d6ee/32.png) [@Heat\_Transfer\_Guy](https://boards.straightdope.com/u/Heat_Transfer_Guy)\ **Post date:** [November 7, 2002, 11:08pm UTC](https://boards.straightdope.com/t/why-metal-objects-feel-colder-than-wood-ones/135794/1 "2002-11-07T23:08:41Z")
[http://www.straightdope.com/classics/a1\_117b.html](http://www.straightdope.com/classics/a1_117b.html) Thermal conductivity is only one reason why metal surfaces feel colder than wood surfaces. There is another equally important effect at play, which Cecil omits to mention. Wood has a very low heat capacity compared to metal objects. When you touch an object that is at room temperature, heat flows from your hand to the object, which warms the object’s surface. This is a transient heat transfer problem. Transient conduction heat transfer depends on BOTH heat capacity and conductivity. Heat Capacity is the product of density times specific heat. The instantaneous heat transfer from your hand depends upon capacity of the object to absorb heat, as well as the object’s thermal conductivity. If you were to touch two surfaces with the same conductivity, the object with the higher heat capacity (density x specific heat) would feel colder. Heat would flow at a greater rate from your hand into the surface. The proof is simple. Think about plunging your hand into a sink of water that is at room temperature. It feels very cold. Water has a high heat capacity, but relatively low thermal conductivity (about 250 times lower than aluminum). In fact, analysis (lots of calculus) shows that instantaneous heat flux (and hence, the intensity of the cold sensation) is roughly proportional to square root of heat capacity. In comparison, the instantaneous heat flow also depends upon the square root conductivity. So, heat capacity has just as much effect as the thermal conductivity on the sensation of cold you feel when you touch a metal surface. Heat Transfer Guy ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [November 8, 2002, 1:03am UTC](https://boards.straightdope.com/t/why-metal-objects-feel-colder-than-wood-ones/135794/2 "2002-11-08T01:03:52Z")
You know, the name **Heat Transfer Guy** sounds to me like a great name for a superhero. But I get the feeling he’d be in league with the evil Dr. Entropy. ---
**Author:** ![Heat\_Transfer\_Guy](https://avatars.discourse-cdn.com/v4/letter/h/d6d6ee/32.png) [@Heat\_Transfer\_Guy](https://boards.straightdope.com/u/Heat_Transfer_Guy)\ **Post date:** [November 8, 2002, 8:35pm UTC](https://boards.straightdope.com/t/why-metal-objects-feel-colder-than-wood-ones/135794/3 "2002-11-08T20:35:18Z")
More knowledgeable about the thermodynamic power of locomotives, Able to calculate the cooling capacity for tall buildings… Look! Up in the Sky… It’s Heat Transfer Guy ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [November 13, 2002, 6:19pm UTC](https://boards.straightdope.com/t/why-metal-objects-feel-colder-than-wood-ones/135794/4 "2002-11-13T18:19:46Z")
Well, yes and no, **Heat Transfer Guy**. Some numbers would help to compare magnitudes of these properties. From my _Mark’s Standard Handbook for Mechanical Engineers_ and _Mechanical Engineer’s Reference Manual_: **Aluminum:** density = 2732 kg/m[sup]3[/sup] specific heat = 0.481 kJ/(kg_K) heat capacity = 1314 kJ/(m[sup]3[/sup]K) thermal conductivity = 117 Btu/(hrft_F) **Iron:** density = 7900 kg/m[sup]3[/sup] specific heat = .216 kJ/(kg_K) heat capacity = 1706 kJ/(m[sup]3[/sup]K) thermal conductivity = 36 Btu/(hrft_F) **Wood:** density = 400-700 kg/m[sup]3[/sup] specific heat = 2.4 - 2.8 kJ/(kg_K) heat capacity = 1120 - 1680 kJ/(m[sup]3[/sup]K) thermal conductivity = 0.06-0.20 Btu/(hrft_F) **Water:** density = 1000 kg/m[sup]3[/sup] specific heat = 4.177 kJ/(kg_K) heat capacity = 4177 kJ/(m[sup]3[/sup]K) thermal conductivity = 0.319 Btu/(hrft_F) (sorry about mixing units) Now, as **Cecil** said, the thermal conductivity of metals (aluminum and iron, in the examples above) is much greater than that of wood: the difference is about three orders of magnitude. The heat capacity for metals and woods, however, is basically the same. That doesn’t make what you said wrong, because the heat capacity of a material _is_ extremely important in how cold it will feel. It’s just that, in comparing wood and metal, the heat capacity is not all that much different. Additionally, I think your analogy using a sink full of water is flawed. Water _does_ have a high heat capacity and relatively low thermal conductivity; however, the numbers are not hugely different from wood. What you’re overlooking is that, in water, heat can convect away from your hand, so that the actual “heat removal rate” is much larger than the thermal conductivity would imply.