This is so because ice absorbs extra heat from the medium whereas the water does not absorbs extra heat .Hope it will help you!!!!

Ice at 0°C is more effective at cooling than water at the same temperature due to the following reasons:

1. Latent Heat of Fusion:
When water is cooled down to 0°C, it undergoes a phase change from liquid to solid, forming ice. During this process, energy is released in the form of latent heat of fusion. The latent heat of fusion is the amount of heat energy required to convert a substance from a liquid to a solid state or vice versa at its melting/freezing point. In the case of water, it is 334 J/g. This release of energy helps to cool the surrounding environment more effectively than water at the same temperature.

2. Higher Specific Heat Capacity:
The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of 1 gram of that substance by 1°C. Water has a higher specific heat capacity compared to ice. This means that it takes more heat energy to raise the temperature of water than it does for ice. Therefore, when the same amount of heat is absorbed by ice and water at 0°C, the ice will experience a greater temperature decrease compared to water. This makes ice a more effective cooling agent.

3. Insulating Effect:
Ice has a solid crystalline structure with tightly packed molecules. This structure makes it a poor conductor of heat. When ice is in contact with a warmer object, it absorbs heat from the object and begins to melt. However, the melted water forms a thin layer around the ice, insulating it from further heat transfer. This insulating effect slows down the rate of heat transfer, allowing the ice to remain colder for a longer period of time and enhancing its cooling efficiency.

4. Cooling through Evaporation:
When ice is exposed to a warmer environment, it can directly undergo sublimation, where it changes from a solid state to a gaseous state without melting into liquid water. This process absorbs heat energy from the surroundings, resulting in cooling. The evaporation of water molecules from the surface of ice contributes to its cooling effect.

Conclusion:
In summary, ice at 0°C is more effective at cooling than water at the same temperature due to the release of latent heat of fusion, higher specific heat capacity, insulating effect, and the cooling effect of evaporation. These factors combined make ice a superior cooling agent compared to water at the same temperature.