Density

Barbara Pawela                  May Academy
5730 S. Kensington              512 S. Lavergne
Countryside IL 60525            Chicago IL 60644
(708) 482-7908                  (312) 534-6140

Objectives:         
      
      The students will be able to:
        1. Discover that density is a unique physical property of matter.
        2. Find the mass of given materials using balance.
        3. Find the volume of rectangular prisms.
        4. Find the volume of given objects using the water displacement method.
        5. Calculate the density of above mentioned objects using the formula:
           Density = Mass/Volume.                
        6. Find the mass and volume of given liquids.
        7. Calculate the densities of the above mentioned liquids.

Materials needed:
                                                                      
      Four large brown paper bags
      Small acrylic, wood, and styrofoam rectangular prisms, having same 
       dimensions
      Different liquids (such as distilled water, alcohol, corn syrup)
      Materials of different densities to fill paper bags (such as styrofoam, 
       cotton, shredded tissue paper, container with rocks, cans of paint, heavy
       metal objects, etc.)                
      Glass rods (about 15 cm long)
      Small rocks                          Metal objects (such as bolts)      
      50 mL beakers or plastic cups     
      Metric rulers                        Calculators
      Laboratory balances                  Ziploc bags                 
      50 mL graduated cylinders

Strategy:

  Activity I:
       1. Fill two large brown paper bags with light-weight materials, such as
          styrofoam, cotton, shredded tissue paper, etc.
       2. Fill two large brown paper bags with heavy-weight materials, such as
          container filled with rocks, cans of paint, heavy metal objects, etc.
       3. Close the bags and label them.  Make the exterior of the bags look the
          same.
       4. Place the four bags next to each other on a table.  Ask the students 
          if they can tell anything about how heavy each bag is by mere 
          observation.  Ask them to hypothesize about the relative weights of 
          the four bags.  Next have a member of each group come up and pick-up 
          each of the bags and arrange the bags in the order from lightest to 
          heaviest.  Discuss and conclude that although the bags looked very 
          similar and seemed to occupy the same amount of space, they had 
          different weights. 

   Activity II:
       1. Pass out Ziploc bag, containing different objects, to each group.  
          Each bag should contain three rectangular prisms, made of different 
          substances.  One prism can be acrylic, one wood, and one of styrofoam.  
          The other objects can be a small rock, a metal bolt, a cotton ball, 
          etc.  Have the students examine each item, and discuss their 
          observations. 
       2. Have each team measure the rectangular prisms and use the formula, 
          V = L x W x H, to calculate the volumes of the three prisms.
       3. Have each team use the balance to weigh each of the three prisms.
       4. Discuss the fact that although the acrylic, wood, and styrofoam have 
          almost identical volumes, their weights are different.  Discuss, 
          define, and introduce the formula for density determination: D = M/V. 
       5. Students calculate the densities of the three prisms.
       6. Have the students look at the bolt and the rock.  Discuss and conclude 
          that the volume of irregularly-shaped objects found by using the water 
          displacement method. 
       7. Pass out glass rods.  Have the students measure and record the mass of 
          the glass rod.
       8. Fill the graduated cylinder with 20 mL of water.  Tie a piece of 
          thread around the glass rod.  Lower the rod into the water in the 
          cylinder until it is completely submerged.  Do not allow it to touch 
          the sides or bottom of the cylinder.  Use the water displacement 
          method to find the volume of the rods. 
       9. The students calculate the density of the glass rods.
      10. Repeat above procedure, steps 11-13, to find the density of the stone
          and the bolt.
      11. Record findings on data sheet.

   Activity III:
        1. Display three different liquids, labeled, "A", "B", "C".
        2. Have each group find the mass and volume of the given liquids.
        3. Calculate the densities of the given liquids.
        4. Record findings on data sheet.