That whole “molecular level” element brings up an important point: A character cannot perform this trick effectively unless she has at least three dots in an Ability and specialty related to the chemical transformation in question. (Esoterica:

Alchemy, Pharmacopeia/ Poisons, Science: Chemistry or Biochemistry, and so forth.) Without such knowledge, the mage might know that such transformations are possible, yet lack the knowledge to properly connect the dots (or the molecules) involved.

Brief Familiarity