Is when original grain sizes are obliterated so grains become uniform and larger

Recrystallization

Explanation:

Recrystallization is a process in which an initially solidified and crystalline material is redissolved and recrystallized, resulting in crystals of the desired size, shape, purity and yield as the end product. The underlying mechanisms, dissolution and recrystallization can also minimize the internal energy of the crystal to achieve a more global energy balance, resulting in a stable polymorph. Although recrystallization is generally deliberately applied to crystal and process optimization, uncontrolled recrystallization can lead to undesired hydrate and solvate formation or polymorph transformation.

mercury

explanation:

mercury is the least dense because of its size