If you had the necessary means to do it, what would happen if you kept compressing an amount of air indefinitely? Would it eventually become a solid 'block' of air? Would the same thing happen to water? I'm guessing that eventually the molecules would all be pushed together...
With a gas - yes. When hydrogen is compressed under great pressure, it forms a sort-of metal. There is a big lump of metal in the middle of Jupiter which is only solid because it is under such big pressure.
I didn't think you could compress a liquid (thats why hydraulics are so successfull)... I thought that only gas and solid compounds could be compressed. That's my understanding anyway....