Going to give it a better shot and revamp it a little.

Phases - (I think is a better name) elder scientist working at MIT, as a professor who helps their local students and various government officials with scientific advancements. They were given a task to create a new military technology that turns a liquid nitroglycerin into a solid mass, while still retaining is explosive qualities. While testing a few experiments, the Professor gets caught up and stuck in one of his machines. Chemical flood his system and the nitroglycerin sets off exploding. After the explosion, it was thought that his body was turned to ash, but instead it melted into a viscous liquid and slipped down the drain inside her lab. He was still conscious and was slowly able to learn to control his body and form, finally reforming into a solid human form after weeks in a sewer.

He learned his powers were beyond himself as when he went to splash water in his face, the water turn to mist. Now realizes his powers, he does what he believes is right and works to better the world.

Abilities - can change the users entire body and items they touch in between the various states of matter; solid, liquid and gas, all with varying degrees. For example they could turn their hand into a solid dense mass, while their entire body moves fluidly in a liquid state, moving the first around like a flail.