(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

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?

2. Relevant 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

3. 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

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# Homework Help: Thermodynamics - hot item placed in water

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