The particles of a liquid are more packed more closely together than the particles of a gas and therefore don't have as much movement?

no because remember a solid has the particles VERY packed together. So it enables no movement, it cannot adapt if it was put into a round container. Liquid can to some degree shift and be evened out in a container. Gas has very loose particles and can spread out widely in a container, as it effectively has no boundaries.

Apex=True