You can't determine the density of a rock with just its mass. Density is calculated by dividing the mass of an object by its volume.

Here's the formula:

Density = Mass / Volume

To find the density of the rock, you need its volume. You can find the volume by:

* Displacement method: Submerge the rock in a graduated cylinder filled with water and measure the change in water level. That volume is equal to the volume of the rock.

* Geometric method: If the rock has a regular shape (cube, sphere, etc.), you can measure its dimensions and calculate the volume using the appropriate formula.

Once you have the volume, you can calculate the density using the formula above.