The table shows the specific latent heat of fusion for four metals. Substance Specific latent heat of fusion / kJ/kg aluminium 397 copper 205 iron 247 lead ...
Question 1 Report
The table shows the specific latent heat of fusion for four metals.
| Substance | Specific latent heat of fusion / kJ/kg |
|---|---|
| aluminium | 397 |
| copper | 205 |
| iron | 247 |
| lead | 23 |
Which metal requires the most energy to melt 2.0 kg at its melting point?
Answer Details
To melt a given mass of a metal, the energy needed is found from \(E = mL\), so with the same mass (2.0 kg) used for every metal, the energy required is directly proportional to each metal's specific latent heat of fusion.
\[ E_{\text{Al}} = 2.0 \times 397 = 794 \text{ kJ} \qquad E_{\text{Cu}} = 2.0 \times 205 = 410 \text{ kJ} \] \[ E_{\text{Fe}} = 2.0 \times 247 = 494 \text{ kJ} \qquad E_{\text{Pb}} = 2.0 \times 23 = 46 \text{ kJ} \]Since aluminium has the largest specific latent heat of fusion (397 kJ/kg) among the four metals, it requires the most energy (794 kJ) to melt 2.0 kg at its melting point.
So aluminium requires the most energy. A common mistake is to assume the metal with the highest melting point requires the most energy to melt; the energy needed to melt a substance depends on its specific latent heat of fusion, not directly on how hot its melting point is.
Download The App On Google Playstore
Everything you need to excel in your exams
