posted by Lauren .
Explain how the density of the solid and liquid phase would compare.
Your question isn't completely clear, because of the wording; however, I think I know what you mean. If the solid-liquid boundary has a positive slope the solid is more dense than the liquid. This is the usual case. If the solid-liquid boundary has a negative slope the solid is less dense than the liquid. This case is not usual. Water is an example of the latter type.