Density as a Unique Physical Property

Teresa Granito                 Von Steuben M.S.C.
                               5039 N. Kimball Ave.
                               Chicago, IL  60625
                               (312) 534-5100

Objectives:

     The student will:
       1.  Learn how to determine the mass of an object.
       2.  Learn how to determine the volume of an object by two techniques:  
           using volume formulas and displacement of water. 
       3.  Learn how to determine the density of an object.
       4.  Discover that density is a unique physical property of matter.
       5.  Identify an unknown substance.

Materials needed:

       1.  Two shapes of a variety of different, labeled, substances (aluminum, 
           brass, etc.).  One should be easily measurable with a ruler, the 
           other should have an irregular shape. 
       2.  Rulers
       3.  Graduated cylinders
       4.  Calculators
       5.  A list of actual densities
       6.  A variety of "unknowns"

Strategy:

       1.  At each lab station place two different shapes of the same substance 
           and have the students determine which technique of measuring volume 
           is more appropriate (they must use each technique). 
       2.  Have them mass the objects and determine the densities.
       3.  The density of both objects should be placed on the board.
       4.  When all of the students have finished, write the actual densities of 
           the substances on the board. 
       5.  Have the students obtain an unknown and identify it.
       6.  Ask the students what some possible reasons for any differences 
           between the two densities may be. 
       7.  Ask the students what they conclude about the densities of the same 
           objects. 

Summary:

     Because the students are given two different shapes of the same material 
     they not only are practicing two different techniques of determining 
     volume, but also they are discovering that density is a unique physical 
     property of a substance which can be used to identify it.