* Spacing of particles: Gas particles are far apart compared to solids and liquids. This means there is a lot of empty space between the particles.

* Weak intermolecular forces: The attractive forces between gas molecules are very weak. This allows the molecules to move freely and spread out.

* Compressibility: Gases are highly compressible. This means their density can change significantly with changes in pressure.

Density = Mass / Volume

Since gases have low mass compared to their volume, their density is low.

Example: Air, a mixture of gases, has a density of about 1.2 kg/m³. This is significantly lower than the density of water (1000 kg/m³) or steel (7850 kg/m³).