Typically, when you use Transmute: Living Elements, you will receive 14-16 random Volatile elements (Volatile Air, Volatile Earth, Volatile Water, or Volatile Fire) in exchange for 15 Volatile Life. If you use this transmute while in one of the new Cataclysm zones associated with the Elemental Planes, however, the element into which your Volatile Life will transform will be predetermined. For example, if you use Transmute: Living Elements while in Uldum, you will always receive Volatile Air for your efforts.
Here's a list of the affected zones and their corresponding Volatile elements:
Additionally, alchemists with Transmutation specialization will have a chance to receive bonus Volatile elements when completing this transmute. The bonus will be random, though, regardless of which zone you are in.