Question

How much energy would it take to melt 1 aluminum soda can if the can starts out at 20°C, melts at 660°C, and has a mass of 14 g?

Answer 1

Chemistry => Thermochemistry => Enthalpy

We have a material that is heated until it goes from a solid state to a liquid state, that is, it melts.

To calculate the total energy we will take into account two stages:

1. Corresponds to the energy needed to raise the temperature from 20°C to 660°C.

2. The energy needed to melt aluminum at a constant melting temperature (660°C).

We will need the following data that we can find in the literature:

Specific heat of aluminum = 0.896J/g°C

enthalpy of fusion aluminum = 0.322J/g

For stage 1. the energy required will be calculated with the following equation:

`Q=mCp(T_2-T_1)`

Where,

Q is the energy required to raise the temperature

m is the mass of the aluminum soda can, 14g

Cp is the specific heat of aluminum, 0.896J/g°C

T2 is the final temperature, 660°C

T1 is the initial temperature, 20°C

We replace the known data:

`\begin{gathered} Q=14g*0.896(J)/(g\degree C)*(660\degree C-20\degree C) \\ \\ Q=8028.16J \end{gathered}`

For stage 2 the energy required will be calculated with the following equation:

`Q_m=m\Delta H_m`

Where

Qm is the energy required to melt the aluminum soda can

m is the mass, 14g

deltaHm is the enthalpy of fusion aluminum,0.322J/g

The energy required will be:

`\begin{gathered} Q_m=14g*0.322(J)/(g) \\ \\ Q_m=4.508J \end{gathered}`

So, the total energy will be the sum of both energies. So, we will have:

`\begin{gathered} Q_T=Q+Q_m \\ \\ Q_T=8028.16J+4.508J \\ \\ Q_T=8032.668J=8.0kJ \end{gathered}`

Answer: It would take 8.0 kJ to melt 1 aluminum soda can