The Thermos And Thermodynamics : Physics

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The Thermos and Thermodynamics
Physics around Campus

Phoebe Seaver

Physics 102
Spring 2017 In the photo, we see two coffee cups, one that is in an insulated thermos with a lid, and one that is a regular mug open to the air, on a college student’s desk at home during their finals studying. It is well known that as coffee sits in any container, it cools down towards room temperature, making it less tasty to drink once it gets lukewarm or even room temperature. However, if it is too hot, it can burn the drinkers tongue and throat, which is incredibly painful, speaking from experience. The rate at which coffee cools may not seem like a science, but in fact, this plays into the laws of thermodynamics that are present in
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Often, energy is lost to the surroundings, and not directly transferred from one object to the other. However, a perfect thermos would prevent any heat from leaking out or in. Energy in the form of heat can flow between materials inside the thermos to the extent that they have different temperatures; for example, between ice cubes and warm coffee. The transfer of energy continues until a common temperature is reached at thermal equilibrium (Cutnell 2014). Thermal equilibrium occurs when there is no heat flow between two materials, making them essentially the same temperature. This is why the coffee continues to cool down the longer it is exposed to the air, because heat exchange is occurring, and the liquid is cooling down from its original warmth to be more like the room that is it in, as the room has less heat. This is why a thermos causes the coffee to cool down slower, because the thermos provides insulation against the exchange of heat from the outside. The extra insulating layer is actually a vacuum, or absence of air, formed during the construction of the thermos. The best insulator possible is a vacuum, because there 's no air. If there 's no air to transfer heat, then the heat is retained where it is ( The equation for Specific Heat: . In order to cool down a standard 8oz cup of coffee to room
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