What is it when a cup of ice turns to water

I don't really know what your question is asking so I am just going to list a few facts that I think might be what you are asking.

Ice turning into water is a physical change.  The ice is undergoing the process of melting which does not change it chemically (ice and water are chemically identical in the sense that they are both composed of H₂O molecules) and the only difference between water and ice is that water molecules have a higher average amount of energy than the ice molecules do.  When a substance melts, the molecules within the substance gain energy (in the form of heat) which allows them to break the intermolecular forces keeping them together.  Since the melting of ice requires energy, the process is endothermic which means that the ice had to get energy from its surroundings and that water has more energy than ice does as a result of the process (ΔH is positive).

I hope that helps.  Let me know in the comments if anything is unclear or if I did not answer your question.