I'll jump in here on the gas and liquid thing.

My book says "Elements of Fluid Mechanics" on the front cover. Fluid is used as a describer of things that can be either gas or liquid since the basic mechanics can be handled by similiar math stuff (I hated math stuff, when I got to college it was like a car hitting a brick wall when I discovered that my brain wouldn't handle higher math stuff, a sad day).

I can remember being taught that we could use words such as "gas" and "liquid", so named because they are DIFFERENT states of the same thing. If not why use two different words??

Same THING but different STATES. (THING is a scientific word to cover a lot of STUFF)

The fact that you can change from one state to another is good and means that with respect to things moving in them, the gas and liquids act differently.

In each case there is a size of thing moving to gas or liquid relationship that makes little things in gas behave similarly to little things in liquid (sorta, kinda, with some weasel words, depends on who is looking and at what.)

Did I miss anything here??