Calculating energy needed to melt aluminum cans?

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    Aluminum Energy
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Homework Help Overview

The problem involves calculating the energy required to melt aluminum cans, specifically 1500 cans with a given mass and initial temperature. The discussion centers around the application of specific heat and latent heat formulas in the context of thermodynamics.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the equations Q=mcΔT and Q=mL to find the total energy needed. They express uncertainty about their calculations and the correct approach after receiving feedback on their initial answer.

Discussion Status

Participants are engaged in clarifying the calculations and checking the original poster's use of units and values. There is an ongoing exploration of the correct application of the formulas, with some participants prompting for verification of the number of cans and the calculations performed.

Contextual Notes

The original poster mentions a lack of clarity due to a fast-paced explanation from their teacher, indicating potential gaps in understanding the problem setup and calculations.

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Homework Statement


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.
Answer in units of J.

Homework Equations


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

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.
 
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How many cans are you trying to melt?
 
Exactly 1500 Aluminum cans.
 
And how many cans did you use in your calculation?
 
Well, 1500.
 
Check again. Also check your units.
 

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