Calculating energy needed to melt aluminum cans?

In summary, the question asks for the amount of energy needed to melt 1500 aluminum cans with a mass of 13.9 g each, starting at a temperature of 25.5◦C. The specific heat of aluminum is 899 J/kg ·◦C, the latent heat is 3.97 ×10^5 J/kg, and the melting point is 660.4◦C. The equations used are Q=mcΔT and Q=mL. The correct calculation is Q= (13.9)(899)(634.9) = 7933773.89 J. The initial attempt at the solution was incorrect due to incorrect units and not taking into account the amount of cans used
  • #1
MarianaMoon
3
0

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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  • #2
How many cans are you trying to melt?
 
  • #3
Exactly 1500 Aluminum cans.
 
  • #4
And how many cans did you use in your calculation?
 
  • #5
Well, 1500.
 
  • #6
Check again. Also check your units.
 

1. How do you calculate the energy needed to melt aluminum cans?

The energy needed to melt aluminum cans can be calculated by multiplying the mass of the cans (in kilograms) by the specific heat capacity of aluminum (0.902 J/g°C) and the change in temperature (in °C). This equation is expressed as Q = m x c x ΔT, where Q is the energy in Joules, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.

2. What is the specific heat capacity of aluminum?

The specific heat capacity of aluminum is 0.902 J/g°C. This is the amount of energy required to raise the temperature of 1 gram of aluminum by 1 degree Celsius.

3. How much energy is needed to melt a single aluminum can?

The amount of energy needed to melt a single aluminum can depends on its mass and the initial and final temperatures. On average, it takes about 1,000 Joules of energy to melt a 12 oz. aluminum can.

4. Does the thickness of the aluminum can affect the energy needed to melt it?

Yes, the thickness of the aluminum can does affect the energy needed to melt it. Thicker cans will require more energy to melt compared to thinner cans, as they have a greater mass.

5. Can the energy needed to melt aluminum cans be used as a measure of their recycling potential?

Yes, the energy needed to melt aluminum cans can be used as a measure of their recycling potential. The lower the energy needed to melt the can, the more energy-efficient and environmentally friendly the recycling process will be. This is one of the reasons why aluminum cans are highly recyclable and preferred over other materials such as plastic or glass.

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