Question

Why is melting ice a better coolant than water at 0°C?

Answer 1

Melting ice absorbs extra heat, called the latent heat of fusion, without a rise in temperature. To melt 1 g of ice at 0°C, 336 J of heat is needed; to melt 1 kg of ice, 336000 J of heat is needed. Water at 0°C can take heat only by rising in temperature, so it removes much less heat. Hence, for the same mass, melting ice gives a greater cooling effect than water at 0°C.