Here's why:
* Gases have very weak intermolecular forces, allowing their particles to move freely and spread out far apart. This means they have a low density and fewer particles in a given space.
* Liquids have stronger intermolecular forces than gases, causing their particles to be closer together.
* Solids have the strongest intermolecular forces, holding particles in a fixed, rigid structure. This results in the highest density and the most particles in a given volume.
