Final answer:
During metamorphism, the density and crystal size of a metamorphic rock can change compared to the rock it was changed from. Recrystallization of minerals in the rock can result in changes in crystal size and arrangement, which can affect the density of the rock.
Step-by-step explanation:
The density and crystal size of a metamorphic rock can vary compared to the rock it was changed from. During metamorphism, the minerals in the original rock undergo recrystallization, which can result in changes in crystal size and arrangement. The density of the metamorphic rock depends on factors such as the mineral composition and the presence of open spaces or voids within the rock. For example, if a sedimentary rock like limestone is metamorphosed into marble, the crystal size of the calcite minerals in the rock may increase, making the rock more coarse-grained. The density of marble is also usually higher compared to limestone due to the recrystallization process.