Here's why:

* Density is mass per unit volume.

* Water (H₂O) has a density of about 1 g/mL at 4°C.

* Carbon tetrachloride (CCl₄) has a density of about 1.59 g/mL at 20°C.

This means that 1 mL of water weighs 1 gram, while 1 mL of carbon tetrachloride weighs 1.59 grams. Therefore, carbon tetrachloride is denser than water.