i was just wondering, is there a slight chance that sound can be the sixth phase. we all know that the phases are solid, liquid, gas, then plasma, but yeah i'm just wondering if there is a chance....

No.

 

http://news.bbc.co.uk/2/hi/science/nature/3441643.stm

Sound is simply matter in one of the other phases vibrating. You can have sound travel through water (jump in a swimming pool), air (of course), solids (put your ear on a table and tap it), and presumably the other phases such as plasma, although I'd hesitate putting your ear to plasma.

 

No extra phase necessary.

We all know that the phases are solid, liquid, gas, then plasma.

I don't know that and I think that is wrong or at least incomplete. In theoretical physics (and those branches of experimental physics that I am familiar with) phases mean that a substance can be in different states for which some (macroscopic) property significantly differs. For the transition between fluid and gas, for example, a suitable property would be the density. There's other phases and phase transitions that are just less commonly mentioned but just as valid as phases as the classics. Examples:

- Transition between ferromagnetic and paramagnetic state in iron (-> magnetisation)

- Transition between isotropic and nematic phase in liquid crystal systems (-> nematic ordering parameter).

- Different lattice systems (relative positions of the atoms) in crystals (-> dunno).

- Transition from superconducting to non-superconducting state by change in temperature (-> electric resistivity).