Why is Jupiter gaseous rather than solid or liquid? Why is Jupiter made up of gas? If the gravitational pull was strong enough would it compress to form a solid body?
 A: The pull of gravity is strong, but not strong enough to make a solid layer on the surface. When forming, a gas giant collapses until it reaches an equilibrium point where, at each radial "layer", the inward force due to the weight of the gas further out is compensated by the gas pressure. Until this equilibrium is achieved, the pressure, density and temperature are all changing as the system tries to "find" its equilibrium.
Once equilibrium is established it's just a matter of seeing whether the temperature and pressure are such that material will exist in a solid, liquid or gas phase. Near the surface of Jupiter (temperature $\approx 200\,{\rm K}$; $\log_{10}(T/{\rm K})\approx 2.3$), the pressure is much too low for hydrogen gas:

There is no exact surface, but depths one can see to have pressures on the order of hundreds of ${\rm kPa}$ ($\log_{10}(P/{\rm Pa})\approx 5$; the pressure would need to be about $100\,000\times$ higher for solid hydrogen to form at this temperature. The core of Jupiter is thought to be hot and dense enough that it may be a metallic liquid or perhaps solid, but as far as I know this has not been conclusively measured.
