The answer is; liquid phase
The characteristics described in the question are those of a liquid. The forces between liquid particles are weaker than the forces between solid particles because the particles are further apart. The particles are not held in a fixed position in the structure hence it can flow and take the shape of the container in which it is in.
Correct me if I'm wrong, anyone who is more informed on this than I am, but wouldn't it be because of the magnetic fields and whatnot? The longer I think on it, the more I feel like I'm wrong, so don't take my word for it 100%
<span>Heavier atoms make denser materials</span>
Dimitri mastered in Elements
As the gas is heated, the particles will begin to move faster. Likewise if you start to cool a gas, the particles will move slower. Because the gas remains at a constant pressure and volume, the particles cannot spread out so they simply move around the container even faster.
Hope this helps :)