Question

what type of phase change occurs when water changes from a solid to a liquid

Answer 1

I assume this question is related to crystallography (chemistry). If you assume a bcc structure of a cube in a water molecule, you will conclude that when water is solid ice , the density is less. I.e, the space between atoms is more compared to that in its liquid state. When ice melts , it no more floats , it is because of its increase in density due to the destruction of its crystalline stucture.