Density is defined as mass per unit volume.

* Liquids have molecules that are closely packed together, resulting in a higher mass per unit volume.

* Gases have molecules that are widely spaced and move freely, leading to a lower mass per unit volume.

Here are some reasons why liquids have higher density:

* Stronger intermolecular forces: Liquids have stronger intermolecular forces than gases, which hold the molecules closer together.

* Reduced compressibility: Liquids are less compressible than gases, meaning their volume changes less under pressure. This results in a higher density.

* Lower kinetic energy: Molecules in liquids have lower kinetic energy than those in gases, leading to less movement and closer packing.

Examples:

* Water (liquid) has a density of 1 g/mL, while air (gas) has a density of approximately 1.2 kg/m³.

* Mercury (liquid) has a very high density compared to other liquids, due to its strong intermolecular forces.

Therefore, liquids generally have a higher density than gases.