Some Applied Phlebotinum come in multiple states, solid, liquid, gas, plasma, etc. Usually it's necessary to convert it from one state to another in order to use it. May involve Phlebotinum-Handling Equipment.
Sometimes the alternate state is inherently destructive, in which case it is Toxic Phlebotinum.
A practical manner of Holding Back the Phlebotinum. A writer wanting to assess new mind-blowing powers to their phlebotinum can avoid breaking the plot with the mere existence of such a thing by compartmentalizing the excessive powers to a specific state that will simply be used up or destroyed. Due to rarity or difficulty in making more, it never need be mentioned again.
Also can be used to neatly avert the Forgotten Phlebotinum problem. The basic phlebotinum already has established powers that would break the immediate plot if used that way, but instead the writer switches to a new state of the phlebotinum, essentially resetting the list of established powers to zero.
- Literature/Mistborn: It's eventually revealed that the liquid in the Well of Ascension, the metal found near it which makes people into allomancers, and the gaseous mist which can activate latent allomany in people are all different states of the same phlebotinum. Unusually, this isn't revealed until part way through the final book of the trilogy - and indeed the characters themselves don't find out until the epilogue.
- Stargate SG-1: started out with naquadah as a solid material of the Stargate, and running through the blood of Goa'uld. Later liquid naquadah was added as a small weapons ammo, then the refined, denser weapons-grade naquadah, and heavy liquid naquadah for a weapons satellite system. Also branched off this trope into naquadria, a much more powerful, yet inherently unstable and radioactive version; the Toxic Phlebotinum of the series. The Asgard flagship is mentioned as being of a "naquadah-trinium-carbon alloy" too. Essentially they played this trope almost as an ongoing "Phlebotinum States On Demand".
- Star Trek: The familiar dilithium crystal concept was later augmented with the introduction of trilithium, which is only useful for making star-destroying weapons. As such, this is the Toxic Phlebotinum version. Also mentioned is paralithium, which is only used with ion-based propulsion fuel, and relatively unimportant except for its use in creation of trilithium.
- BIONICLE: Protodermis generally comes in liquid, solid, and organic forms. Once raw liquid Protodermis is purified in Ga-Metru, it goes to Ta-Metru to be heated and then cooled to harden in ordered to be used in building and crafting as solid Protodermis.
- Antidermis comes in liquid and gaseous forms, as well as solid if frozen.
- Phazon in Metroid Prime games comes in liquid and solid forms (the solid form seems to also sometimes be crystalline and sometimes for veinlike growths). The liquid form is unstable and explosive. Additionally the Impact Crater in the first game contains "orange phazon" (it's never given an actual name in the game, but it looks like phazon except it's orange) which is much more radioactive.
- Command & Conquer: Tiberian Series has Tiberium, which appears in several different states and forms.
- The most iconic form is a greenish crystalline substance which "grows" section by section, gradually taking over whatever it touches. There are also blue crystal forms that are highly explosive, and a liquid form that is insanely volatile and be used to make superweapons. And then there are the stranger forms the Scrin can come up with, like the Corruptor's less volatile, more bio-reactive liquid state.
- Mystic Energy in Phaeton can imitate solid, liquid, gas, plasma, gel, fog and states yet unknown to us, but in truth is actually none of these things.
- Truth in Television: Almost everything comes in multiple states, solid, liquid, and vapor, along with non-Newtonian substances such as Oobleck.
- However, the solid/liquid/gas phase is generally trivial to interchange. Structural differences (carbon vs graphite vs diamond) are often not trivial to interchange. Isotopes are most often separated out of a naturally occurring mixture. When isotopes need to be made, they often are made from completely unrelated elements, but in some cases are made from another isotope of the same element.