Allankles
Kwisatz Haderach
There are books out there that discuss Superman's powers from a real world scientific perspective. I think there's a book out called The Science of Superman , that has scientific explanations on Supes. Superman's powers have been elaborated more than any other super hero.
From what I've heard his strength is related to 2 physical aspects:-
High sub atomic density - that makes him "harder" and stronger than any human.
And secondly, his capacity for some kind of photosynthesis, and energy absorption. Charging his cells and allowing him to achieve greater feats of strength and durability.
His durability - is related to his cells ability to manipulate the stored energy within his body to generate a bio electric field. Coupled with his harder body, resulting from his high sub atomic density.
His flight - is related to his ability to manipulate gravitons (hypothetical particles related to gravity in physics). He posseses some degree of psionic power and therefore can manipulate this particles around him, allowing him the ability of flight.
His freeze breath - is basically his ability to reduce the kinetic energy of particles around him. It's similar to any person blowing out cool breathe except with Supes, he can do it to a much greater degree thanks to his enormous lung capacity etc
His heat vision is basically a form of psionic control of kinetic energy i.e it is a form of TK. Through his eyes, he can project telekinetic power, exciting air particles to form heat energy to whatever degree he wishes.
Supes has a lot TK ability to go along with his strength and durability.