During one of the lab sessions that I attended, we observed a peculiar phenomenon. Before us were two small blocks— one made of aluminum and one made of plastic. When we touched each of the blocks, we noticed that the aluminum block was much cooler to the touch than the plastic block. We then put an ice cube on both the aluminum and the plastic blocks. Astonishingly, the ice melted faster on the cold aluminum block than on the plastic block. This experiment seemed to defy our logic; should not the ice have melted on the warmer, plastic block? The science behind this paradox has to do with the materials’ thermal conductivities. A material’s thermal conductivity refers to its ability to facilitate the flow of heat from a warmer surface to a …show more content…
Aluminum’s thermal conductivity, k, is 205 W/mK (“Thermal Conductivity of Materials and Gases”). Hence, it is good at facilitating the transfer of heat. Because of its abilities as a conductor, the aluminum was able to transfer heat from itself (the warmer surface) to the ice cube (the colder surface), melting the ice cube. On the other hand, plastic is considered to be a poor conductor of heat; it’s thermal conductivity is about 0.2 W/mK (“Thermal Conductivity of Materials and Gases”). In fact, plastic is generally considered to be an insulator. Instead of facilitating the transfer of heat between surfaces, an insulator traps heat and does not allow heat to flow in or flow out. Because plastic is not a good conductor, it was not able to transfer heat to the ice cube as quickly as the aluminum was able to. Thus, the ice melted slower on the plastic than it did on the aluminum. Although the aluminum block felt colder than the plastic block, both materials were actually at the same temperature. The reason we perceived the aluminum block to feel colder than the plastic was again related to its thermal conductivity. When we touch a material like aluminum, heat flows out of our fingertips and through the aluminum. This loss of heat from our fingertips makes us perceive the aluminum to be colder (Ackerson). When we touch plastic, heat does not flow out of our fingertips through the plastic as well as it does with aluminum, so we do not observe the plastic to be as cold as the