- #1
portofino
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Homework Statement
A 900 g aluminum pan is removed from the stove and plunged into a sink filled with 12.0 L of water at 19.0 degrees. The water temperature quickly rises to 24.5 degrees.
What was the initial temperature of the pan in degrees C?
What was the initial temperature of the pan in degrees F?
Homework Equations
Q_net = 0 where Q is heat
No phase changes involved so no latent heats required
C1 = specific heat capacity, aluminum: 900 J/kg-K
C2 = Specific heat capacity, water: 4.184 kJ/kg-K = 4184 J
Q_net = (C1)(M1)(T) + (C2)(M2)(T2) = 0
where C1 = 900, C2 = 4184, M1 = 900g = 0.9 kg, M2 = 12kg because 1 L water = 1 kg, T = unknown, T2 = 24 - 19 = 5 degrees
Tc = T - 273.15 where Tc is temp in celsius, T is temp in kelvin
Tf = 9/5(Tc) + 32 where Tf is temp in fahrenheit, Tc is temp in celsius
The Attempt at a Solution
Q_net = (C1)(M1)(T) + (C2)(M2)(T2) = 0
no phase changes involved, no latent heats needed
= (900)(0.9)(T) + (4184)(12)(24-19)
= (900)(0.9)(T) + (4184)(12)(5)
T = -[(4184)(12)(5)] / [(900)(0.9)] = -309 degrees
I assumed that -309 was in kelvin, thus used the above equation to solve for temperature in celsius.
i noticed that the temp was negative, thus decided that since the water temp increased, the temperature had to be positive, thus -309 became 309, and using the kelvin-->celsius conversion i got 36 degrees Celsius which was incorrect?
as for the second part, the initial temp in fahrenheit, i need to solve the first part to get it.
what did i do wrong? it seems like a straightforward problem, i think i missed something.
thanks