The question requires us to provide the mass of iron when 100g of this metal is heated above its melting point.
A phase change is a physical process in which a substance goes from one phase to another. A phase change usually occurs when heat is added or removed from a substance. The melting point is the temperature at which the substance goes from a solid to a liquid (or from a liquid to a solid).
It is important to notice that there isn't a significant change in mass when a phase change occurs. This means that if 1 g of a solid substance is heated enough to melt and transform in a liquid, the liquid form will present the same mass as the solid.
Now, considering the information above and the data provided by the question, we can say that when 100 g of solid iron is heated above its melting point, the mass of the molten iron will be 100 g.