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A-student-seals-200g-of-ice-cold-water-in-a-glass-vacuum-thermos-flask-and-finds-that-it-warms-up-by-3-5-K-in-one-hour-SHC-of-water-2400-Jkg-1-K-1-a-Calculate-the-average-rate-of-heat-flow




Question Number 75648 by Rio Michael last updated on 14/Dec/19
 A student seals 200g of ice−cold water in a glass vacuum  (thermos) flask and finds that it warms up by 3.5 K in one hour  SHC of water =2400 Jkg^(−1) K^(−1)   a) Calculate the average rate of heat flow in the flask in watts.  To check this result over a longer period,the student fills the flask with  equal amounts of ice and water all at 0°C, and leaves it for   4 hours. the specific latent heat(enthalpy) of fusion of ice is 0.33MJg^(−1)   b) How much ice would you expect to have melted at the end of the  four hours?
$$\:{A}\:{student}\:{seals}\:\mathrm{200}{g}\:{of}\:{ice}−{cold}\:{water}\:{in}\:{a}\:{glass}\:{vacuum} \\ $$$$\left({thermos}\right)\:{flask}\:{and}\:{finds}\:{that}\:{it}\:{warms}\:{up}\:{by}\:\mathrm{3}.\mathrm{5}\:{K}\:{in}\:{one}\:{hour} \\ $$$${SHC}\:{of}\:{water}\:=\mathrm{2400}\:{Jkg}^{−\mathrm{1}} {K}^{−\mathrm{1}} \\ $$$$\left.{a}\right)\:{Calculate}\:{the}\:{average}\:{rate}\:{of}\:{heat}\:{flow}\:{in}\:{the}\:{flask}\:{in}\:{watts}. \\ $$$${To}\:{check}\:{this}\:{result}\:{over}\:{a}\:{longer}\:{period},{the}\:{student}\:{fills}\:{the}\:{flask}\:{with} \\ $$$${equal}\:{amounts}\:{of}\:{ice}\:{and}\:{water}\:{all}\:{at}\:\mathrm{0}°{C},\:{and}\:{leaves}\:{it}\:{for}\: \\ $$$$\mathrm{4}\:{hours}.\:{the}\:{specific}\:{latent}\:{heat}\left({enthalpy}\right)\:{of}\:{fusion}\:{of}\:{ice}\:{is}\:\mathrm{0}.\mathrm{33}{MJg}^{−\mathrm{1}} \\ $$$$\left.{b}\right)\:{How}\:{much}\:{ice}\:{would}\:{you}\:{expect}\:{to}\:{have}\:{melted}\:{at}\:{the}\:{end}\:{of}\:{the} \\ $$$${four}\:{hours}? \\ $$

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