What is the SI unit of mass density of a substance ?

Explanation

To determine the SI unit of mass density of a substance, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Mass Density**:
Mass density (often denoted as ρ) is defined as the mass of an object divided by its volume. The formula for mass density can be written as:
\[
\text{Density} (\rho) = \frac{\text{Mass (m)}}{\text{Volume (V)}}
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