- #1
jaded18
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The system, originally at T_A = 21.0 Celsius, is placed in a freezer, where energy is removed from it in the form of heat at a constant rate. The figure shows how the temperature of the system takes t_1 = 10 min = 600 s to drop to 0 Celsius, after which the water freezes. Once the freezing is complete, the temperature of the resulting ice continues to drop, reaching temperature T_B after an hour.
http://session.masteringphysics.com/problemAsset/1013967/12/1013967B.jpg
If the cooling power remains constant, what will be the temperature of the system T_B after it has been in the freezer for exactly 1 hour? This temperature is off scale on the figure.
also: latent heat of fusion (ice to water phase change at 0 Celsius) = 333.7J/g
____________________
I know that after the water cools to 0 Celsius and freezes, the time that remains before the one hour mark is 722 sec and that the constant cooling power is 36.6J/s which I got by determining how much energy that has to be transferred out of the system as heat Q to lower its temperature to 0 =(2.20*10^4) and dividing it by 600s.
So... that means that in addition to 2.20*10^4 J that was required to bring the T from 21 to 0, we have to consider the energy for phase change (Q=mL=250(333.7)) and also the energy that I calculated to be 26425.2 J in the very beginning with the cooling power and time.
I feel like I'm going around in circles. Help?
http://session.masteringphysics.com/problemAsset/1013967/12/1013967B.jpg
If the cooling power remains constant, what will be the temperature of the system T_B after it has been in the freezer for exactly 1 hour? This temperature is off scale on the figure.
also: latent heat of fusion (ice to water phase change at 0 Celsius) = 333.7J/g
____________________
I know that after the water cools to 0 Celsius and freezes, the time that remains before the one hour mark is 722 sec and that the constant cooling power is 36.6J/s which I got by determining how much energy that has to be transferred out of the system as heat Q to lower its temperature to 0 =(2.20*10^4) and dividing it by 600s.
So... that means that in addition to 2.20*10^4 J that was required to bring the T from 21 to 0, we have to consider the energy for phase change (Q=mL=250(333.7)) and also the energy that I calculated to be 26425.2 J in the very beginning with the cooling power and time.
I feel like I'm going around in circles. Help?