130 grams of boiling water (temperature 100° C, heat capacity 4.2 J/gram/K) are
ID: 1631331 • Letter: 1
Question
130 grams of boiling water (temperature 100° C, heat capacity 4.2 J/gram/K) are poured into an aluminum pan whose mass is 950 grams and initial temperature 24° C (the heat capacity of aluminum is 0.9 J/gram/K). (a) After a short time, what is the temperature of the water?
Tfinal = ??? C
Next you place the pan on a hot electric stove. While the stove is heating the pan, you use a beater to stir the water, doing 19913 J of work, and the temperature of the water and pan increases to 79.0° C. How much energy transfer due to a temperature difference was there from the stove into the system consisting of the water plus the pan?
Q = ???? J
Explanation / Answer
(A) Suppose final temp is T then
Energy released by water = Energy absorbed by aluminium
130 x 4.2 x (100 - T) = 950 x 0.9 x (T - 24)
54600 - 546 T = 855 T - 20520
T = 53.6 deg C .......Ans
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Energy needed = (130 x 4.2 x ( 79 - 53.6)) + (950 x 0.9 x (79 - 53.6))
= 35585.4 J
35585.4 = Q + 19913
Q = 15672.4 J .......Ans
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