Change in Physical State. Heat also affects how molecules interact with each other. Heating a solid above a certain temperature will cause it to melt to form a liquid; further heating causes this liquid to boil to form a vapor.
When water is in its solid state (ice) , the water molecules are packed close together preventing it from changing shape. Ice has a very regular pattern with the molecules rigidly apart from one another connected by the hydrogen bonds that form a crystalline lattice.
3.3 Phase Changes How does the arrangement of water molecules change during melting and freezing? The arrangement of molecules in water becomes less orderly as water melts and more orderly as water freezes. Melting and Freezing