Select Tools->Material Properties... to bring up the material properties dialog. Select the solid to assign the material to and select a material from the material library. Press the OK button and the density associated with the selected material will be assigned to the selected solid.
Select Tools->Customer Name Tools->Create Part Property Expressions
or press the Create Part Property Expressions
toolbar icon. The following dialog will
appear:

Select the reference set to determine what solids are to be included in the calculations.

Make sure the Select Solids button is selected. Select the solids to include in the calculations in the graphics window.
Choose the units the calculations will be in.
Go to Tools->Expressions to bring up the expression editor, we should notice that there are now four new expressions called: PPVolume, PPMass, PPSolidDensity, and PPSurfaceArea. You should not be able to delete or modify the expressions. Changing any of the calculation solids' parameters should also automatically update the expression values.
The note will use these expressions by way of interpart expressions to display the values.