It all depends on the number of particles in your sample.
A billion particles will have a greater volume than one particle.
If you have the same number of particles, then the gas will have the greater volume.
The particles of matter in the solid state are close together and fixed in place.
(From www.columbia.edu)
The particles of matter in the liquid state are still close together but they are far enough apart to move freely.
The particles of matter in the gaseous state are neither close together nor fixed in place. The gas expands to fill its container.
Thus, a given number of particles will have the greatest volume in the gas state.
