* Spacing of particles: Gas particles are widely spaced compared to liquids and solids.

* Free movement: Gas particles move freely and randomly, constantly colliding with each other and the container walls.

* Compressibility: Gases are highly compressible because the large spaces between particles allow them to be squeezed closer together.

Density is a measure of mass per unit volume. Since gases have a lot of empty space, their mass is spread out over a larger volume, resulting in low density.