Mass is the amount of matter in an object. The mass of an object can be measured with a balance scale. The unit for mass is cubes. When the pans contain exactly the same mass, the beam is in balance. 1. Make sure the balance scale is balanced. 2. Place your rock in one side of the balance scale. Notice how the balance is no longer balanced. 3 Add cubes until the scale is balanced. Take a of your rock and the cubes in the balance scale. 4. Count up the cubes. 5. Use the label tool to write the mass of the rock on the picture. Don't forget to write your unit (cubes). 6. Record a summary of this activity. Be sure to use the words mass, cubes, and balance scale.