What amount of heat must be spent to melt an aluminum bar weighing 20 kg, taken at a temperature of 20C.

Data: m (mass of an aluminum bar) = 20 kg; t (temperature at which the bar was taken) = 20 ºС.
Constants: С (specific heat of aluminum) = 920 J / (kg * ºС); tmelt (temperature of the beginning of aluminum melting) ≈ 660 ºС; λ (specific heat of fusion of aluminum) = 3.9 * 10 ^ 5 J.
The amount of heat that was spent for melting an aluminum bar: Q = C * m * (tmelt – t) + λ * m.
Calculation: Q = 920 * 20 * (660 – 20) + 3.9 * 10 ^ 5 * 20 = 19576000 J ≈ 19.6 MJ.
Answer: You need to spend 19.6 MJ of heat.