What is the unit of density?

Density is defined as the mass of a substance per unit volume. The standard unit of measurement for density in the International System of Units (SI) is kilograms per cubic meter, represented as kg/m³. This unit composition directly reflects the relationship between mass (in kilograms) and volume (in cubic meters), making it easy to understand the concentration of matter in a given space.

The other units in the options pertain to different physical quantities. For instance, the Pascal (Pa) is a unit of pressure, kg is the unit of mass alone without reference to volume, and the Newton is a unit of force. None of these options encapsulate the concept of density, which specifically involves both mass and volume. Thus, the choice of kg/m³ is accurate and widely accepted for expressing density in physics and engineering contexts.