How much energy is required to melt 7.00 kg of aluminum already at its melting point? Use Lf(aluminum) = 380 kJ/kg.

1. Apply Q = mLf with m = 7.00 kg and Lf = 380 kJ/kg. 2. Multiply: Q = 7.00 x 380 = 2660 kJ. 3. 380 kJ would only melt 1.00 kg, not the full 7.00 kg. 4. 54.3 kJ is far too small for this mass, and 1900 kJ corresponds to 5.00 kg rather than 7.00 kg. 5. So 2660 kJ is correct. _Source: OpenStax Physics (CC BY 4.0), Ch 11 "Thermal Energy, Heat, and Work", section 11.3 Phase Change and Latent Heat_