Final answer:
The density of the unknown substance is 6 g/cm³.
Step-by-step explanation:
The density of a substance can be calculated by dividing its mass by its volume. In this case, the mass of the cube is 162g. To find the volume, we need to cube the edge length. Since all the sides of the cube measure 3cm, the volume is 3cm * 3cm * 3cm = 27cm³. Now, we can calculate the density by dividing the mass by the volume:
Density = mass / volume
Density = 162g / 27cm³ = 6 g/cm³