Final answer:
The usual units of density for liquids are grams per cubic centimeter (g/cm³) or grams per milliliter (g/mL). Gases, on the other hand, are typically reported in grams per liter (g/L).
Step-by-step explanation:
The usual units of density for liquids are grams per cubic centimeter (g/cm³) or grams per milliliter (g/mL). These units are commonly used because they provide a convenient way to express the density of solids and liquids. On the other hand, the density of gases is often reported in grams per liter (g/L) since gases have much lower densities compared to solids and liquids.