During the melting of ice in an ice-water mixture, what happens to the internal energy?

During the melting of ice in an ice-water mixture, the internal energy of the system increases. This increase occurs because energy in the form of heat is absorbed by the ice as it transitions from a solid to a liquid state. The process of melting requires energy to overcome the intermolecular forces holding the ice molecules together.

As the ice gains this energy, it is used to break the hydrogen bonds between water molecules rather than raising the temperature of the mixture. This adds to the internal energy of the system. The temperature of the mixture may remain constant during this phase change until all the ice has melted, but the internal energy is indeed increasing due to the heat absorption. Thus, the correct understanding of the thermodynamic process during melting is that the internal energy increases as heat is added, leading to the phase change from solid to liquid.