To make it clear pet talk about melting of ice
when we apply heat to ice,its temperature increses and reach 0°c,then after that when we apply heat,the temperature wont increase rather heat is used to phase change,this heat uses is called latent heat of fusion.After complete phase change,then again temperature increase with heat supplied
Thus water at 0°c contain extra energy of latent of fusion,that is why water at 0°c has more energy that ice at 0°c