The melting point of aluminum is 660°C,its latent heat of fusion is 4.00 × 10⁵ J/kg,and its specific heat is 900J/kg ∙ K.How much thermal energy must be added to 500 g of aluminum originally at 27°C to completely melt it?

Question

Quizplus · Accepted Answer

To completely melt the aluminum, we need to add thermal energy to raise its temperature from 27°C to 660°C and then to undergo the phase transition (melting) at 660°C. The thermal energy required can be calculated as follows:

Q = (m × c × ΔT) + (m × Lf)

where Q is the thermal energy required, m is the mass of aluminum, c is the specific heat of aluminum, ΔT is the temperature difference (660°C - 27°C), and Lf is the latent heat of fusion of aluminum.

Substituting the given values, we get:

Q = (0.5 kg × 900 J/kg ∙ K × (660°C - 27°C)) + (0.5 kg × 4.00 × 10^5 J/kg)

Q = 484500 J = 484.5 kJ

Therefore, the thermal energy required to completely melt 500 g of aluminum is 485 kJ. Hence, the best choice is (A).

The Melting Point of Aluminum Is 660°C,its Latent Heat of Fusion