Discussion
The amount of heat to be withdrawn from 3 kg of water at 0°C to obtain 3 kg of ice at 0°C in an icemaker is (latent heat of fusion of ice is 80 kcal/kg)
Answer: E
The heat withdrawn is 240 kcal.
Water and ice are both at \(0^{\circ}\)C, so only the latent heat of fusion is removed:
\[ Q = mL = 3 \times 80 = 240\ \text{kcal} \]
80 kcal is the amount for 1 kg, and 160, 320 and 400 kcal correspond to 2, 4 and 5 kg.
Removing the same heat from water already at 0°C changes its state without lowering its temperature; cooling to below 0°C would need the specific heat of ice as well, which this question does not involve.
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