Here's why:

* Density is mass per unit volume.

* The arrangement of molecules plays a crucial role in density. In solids, molecules are tightly packed and arranged in a regular, repeating pattern. In liquids, they are less tightly packed and can move around more freely.

* However, the type of molecule also matters. Some molecules have stronger intermolecular forces than others, leading to tighter packing even in liquid form.

Examples of liquids denser than solids:

* Water: Ice (solid water) is less dense than liquid water. This is why ice floats.

* Mercury: Mercury is a liquid at room temperature and is denser than its solid form.

In summary: While it's a common misconception, the density of liquids compared to solids depends on the specific substance.