Ice at 273K (0°C) is more effective in cooling than water at the same temperature due to the latent heat of fusion. Here's why:
Latent Heat of Fusion: When ice melts to water, it absorbs heat from the surroundings without changing its temperature. This is called the latent heat of fusion. The energy required to melt 1 kg of ice at 0°C is about 334 J. This process requires energy to break the bonds between the water molecules in the solid phase, and that energy comes from the surroundings, thereby cooling them down.
Heat Transfer: When ice is in contact with a substance, such as a warm drink, it absorbs heat to melt. Since the temperature of the ice stays at 0°C while melting, it can absorb a larger amount of heat (due to the latent heat) before its temperature rises. Water at 273K, on the other hand, would not absorb as much heat to change its state, and any heat added would increase its temperature instead.
In summary, ice at 273K is more effective at cooling because it absorbs more heat as it melts, without an increase in temperature, compared to water, which would simply warm up if heat is added.