question: why does metal always feel cold even if the room is warm?
comment: Because even a warm room is probably cooler than your body. Because metal transfers heat exceptionally well (it's why we use it for cooking), it will pull heat from your body faster than even the air around you, causing the point of contact to feel colder.
passages: "Internal" chills are pieces of metal that are placed inside the molding cavity. When the cavity is filled, part of the chill will melt and ultimately become part of the casting, thus the chill must be the same material as the casting. Note that internal chills will absorb both heat capacity and heat of fusion energy.
   Section::::Alloy steels.
   This table shows the resistivity ("ρ"), conductivity and temperature coefficient of various materials at 20 °C (68 °F, 293 K)
  
  The effective temperature coefficient varies with temperature and purity level of the material. The 20 °C value is only an approximation when used at other temperatures. For example, the coefficient becomes lower at higher temperatures for copper, and the value 0.00427 is commonly specified at .
  
  The extremely low resistivity (high conductivity) of silver is characteristic of metals. George Gamow tidily summed up the nature of the metals' dealings with electrons in his popular science book "One, Two, Three...Infinity" (1947):
   The underlying mechanism of the effect is not fully established; in particular, different textbooks give conflicting explanations. However, as with any isolated (adiabatic) temperature change, the effect comes from the voltage raising or lowering the entropy of the system. (The magnetocaloric effect is an analogous, but better-known and understood, phenomenon.)
  
  Electrocaloric materials were the focus of significant scientific interest in the 1960s and 1970s, but were not commercially exploited as the electrocaloric effects were insufficient for practical applications, the highest response being 2.5 degrees Celsius under an applied potential of 750 volts.
   Copper has a thermal conductivity of 231 Btu/(hr-ft-F). This is higher than all other metals except silver, a precious metal. Copper has a 60% better thermal conductivity rating than aluminium and a 3,000% better rating than stainless steel.
  
  Further information about the thermal conductivity of selected metals is available.
  
  Section::::Beneficial properties of copper heat exchangers.:Corrosion resistance.
   Near room temperature, the resistivity of metals typically increases as temperature is increased, while the resistivity of semiconductors typically decreases as temperature is increased. The resistivity of insulators and electrolytes may increase or decrease depending on the system. For the detailed behavior and explanation, see Electrical resistivity and conductivity.
   According to the laws of thermodynamics, all particles of matter are in constant random motion as long as the temperature is above absolute zero. Thus the molecules and atoms which make up the human body are vibrating, colliding, and moving. This motion can be detected as temperature; higher temperatures, which represent greater kinetic energy in the particles, feel warm to humans who sense the thermal energy transferring from the object being touched to their nerves. Similarly, when lower temperature objects are touched, the senses perceive the transfer of heat away from the body as feeling cold.
   Section::::Causes of conductivity.:Superconductivity.
  
  The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source.
   As the temperature of the metal is sufficiently reduced (so as to 'freeze' all the phonons), the resistivity usually reaches a constant value, known as the residual resistivity. This value depends not only on the type of metal, but on its purity and thermal history. The value of the residual resistivity of a metal is decided by its impurity concentration. Some materials lose all electrical resistivity at sufficiently low temperatures, due to an effect known as superconductivity.
   Section::::History.:2017.
   Section::::History.
  
  Section::::History.:2015-2016.
   Platinum was proposed by Sir William Siemens as an element for a resistance temperature detector at the Bakerian lecture in 1871: it is a noble metal and has the most stable resistance–temperature relationship over the largest temperature range. Nickel elements have a limited temperature range because the amount of change in resistance per degree of change in temperature becomes very non-linear at temperatures over 300 °C (572 °F). Copper has a very linear resistance–temperature relationship; however, copper oxidizes at moderate temperatures and cannot be used over 150 °C (302 °F).
   One must be careful when measuring temperature to ensure that the measuring instrument (thermometer, thermocouple, etc.) is really the same temperature as the material that is being measured. Under some conditions heat from the measuring instrument can cause a temperature gradient, so the measured temperature is different from the actual temperature of the system. In such a case the measured temperature will vary not only with the temperature of the system, but also with the heat transfer properties of the system.
   In physics, a metal is generally regarded as any substance capable of conducting electricity at a temperature of absolute zero. Many elements and compounds that are not normally classified as metals become metallic under high pressures. For example, the nonmetal iodine gradually becomes a metal at a pressure of between 40 and 170 thousand times atmospheric pressure. Equally, some materials regarded as metals can become nonmetals. Sodium, for example, becomes a nonmetal at pressure of just under two million times atmospheric pressure.
   Metals are shiny and lustrous, at least when freshly prepared, polished, or fractured. Sheets of metal thicker than a few micrometres appear opaque, but gold leaf transmits green light.
   with "k" a constant. For pure metals such as copper, silver, etc. "k" is large, so the thermal conductivity is high. At higher temperatures the mean free path is limited by the phonons, so the thermal conductivity tends to decrease with temperature. In alloys the density of the impurities is very high, so "l" and, consequently "k", are small. Therefore, alloys, such as stainless steel, can be used for thermal insulation.
  
  Section::::Theoretical prediction.:Lattice waves.
   In order for energy balance to be maintained, the heat lost through the outer surface of the outer wall must be equal to the heat absorbed by the inner surface of the outer wall,
  
  Since the absorptivity of polished silver is the same as its emissivity, we can write
   Silver, a precious metal, is the only metal with a higher electrical conductivity than copper. The electrical conductivity of silver is 106% of that of annealed copper on the IACS scale, and the electrical resistivity of silver = 15.9 nΩ•m at 20 °C. The high cost of silver combined with its low tensile strength limits its use to special applications, such as joint plating and sliding contact surfaces, and plating for the conductors in high-quality coaxial cables used at frequencies above 30 MHz
  
  Section::::Properties of copper.:Tensile strength.
   Section::::History.:Middle Ages.
   Section::::Calibration.
  
  Section::::Calibration.:Temperature sensors.
   As a consequence, the resistance of wires, resistors, and other components often change with temperature. This effect may be undesired, causing an electronic circuit to malfunction at extreme temperatures. In some cases, however, the effect is put to good use. When temperature-dependent resistance of a component is used purposefully, the component is called a resistance thermometer or thermistor. (A resistance thermometer is made of metal, usually platinum, while a thermistor is made of ceramic or polymer.)
   Section::::Metals.
   Section::::Wheal Metal today.
   Section::::Physics.:Changing a material's Curie temperature.
  
  Section::::Physics.:Changing a material's Curie temperature.:Composite materials.
  
  Composite materials, that is, materials composed from other materials with different properties, can change the Curie temperature. For example, a composite which has silver in it can create spaces for oxygen molecules in bonding which decreases the Curie temperature as the crystal lattice will not be as compact.
   Section::::History.:Antiquity.
  