* Intensity is a measure of the power transferred per unit area. It's often used to describe the strength of a wave, like light or sound.

* Mass per unit volume is density. It describes how much mass is contained within a given volume.

Here's a breakdown:

* Intensity: Units are typically Watts per square meter (W/m²)

* Density: Units are typically grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³)

Think of it this way:

* Intensity is like the brightness of a light bulb, while density is like the weight of the bulb itself.