Maximum Heat Transfer by Liquids at Different Temperatures

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Set the initial temperature and mass of a sample of liquid to calculate the maximum quantity of heat it can transfer when its temperature changes by The process is described by the equation , where is heat transferred (J), is mass (g), is specific heat of the substance (J/g °C), and is temperature (°C). Each liquid has a characteristic specific heat.

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In the study [1] that inspired this work, a quantity of liquid was added to a massive amount of liquid nitrogen, so the final temperature winds up at 77 K ( degrees °C), whatever the mass and original temperature of the liquid. The purpose of this Demonstration is thus to clarify the conceptual difference between temperature and heat.

Temperature is a measure of the average kinetic energy of the molecules in a body. Thus, temperature is an intensive property, independent of mass, while heat is an extensive property, proportional to the mass. A system does not "contain" any definite quantity of heat, but can only transfer heat along a temperature gradient.

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Contributed by: Desi Dikova, Kaylie Sierra and Franco Szeto (March 2017)
Open content licensed under CC BY-NC-SA


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References

[1] E. Vitz and M. J. Schuman, "The Paradox: Which 'Contains More Heat,' a Cup of Coffee at 95 °C or a Liter of Icewater?," Journal of Chemical Education, 82(6), 2005 pp. 856–860. doi:10.1021/ed082p856.

[2] The Engineering Toolbox. "Liquids and Fluids: Specific Heats." (Mar 23, 2017) www.engineeringtoolbox.com/specific-heat-fluids-d_ 151.html.



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