Calculating energy needed to melt aluminum cans?

1. Jan 31, 2013

MarianaMoon

1. The problem statement, all variables and given/known data
You have collected exactly 1500 aluminum cans for recycling, each with a mass of 13.9 g. How much energy is needed to melt them if their initial temperature is 25.5◦C? Assume
the speciﬁc heat, the latent heat and the melting point of aluminum are 899 J/kg ·◦C, 3.97 ×10^5 J/kg and 660.4◦C, respectively.

2. Relevant equations
I'm pretty sure that the equations used are Q=mcΔT, and after getting that, using the Q=mL formula..

3. The attempt at a solution
So, for the Q=mcΔT part, I put; Q= (13.9)(899 J/kg◦C)(634.9)+(13.9)(397000 J/kg) which is 1.34*10^7. I put it in my homework online and it said it was incorrect. I later did Q=(13.9)(899)(634.9) which was 7933773.89 and then put it into Q=ml.. 7933773.89=13.9(397000) and it calculated to be 7933773.89=5518300. Do I subtract, divide? I have a feeling I'm doing it wrong. I don't know what to do after this step, my teacher was explaining it at the end of class really fast and I didn't get to finish writing down the notes.

2. Jan 31, 2013

tms

How many cans are you trying to melt?

3. Jan 31, 2013

MarianaMoon

Exactly 1500 Aluminum cans.

4. Jan 31, 2013

tms

And how many cans did you use in your calculation?

5. Jan 31, 2013

MarianaMoon

Well, 1500.

6. Jan 31, 2013

tms

Check again. Also check your units.