How come water doesnt change as it melts from solid to liquid water?

Answer 1

Water does change as it melts from a solid to liquid. That's the change. Its molecules speed up and separate from the lattice structure structure of the ice and become fluid. This is called a physical change because the water molecules themselves do not undergo a change. Solid water and liquid water are still water.

If you're talking about temperature, the temperature does not change during the phase change. That's because the heat energy is being used to remove water molecules from the lattice structure. Once all of the water molecules a separated, the temperature can increase.