`Density in Relation to Float and SinkCarolyn C. Roberson-Ellis       Morton Career Academy                                 401 N. Troy                                Chicago, Illinois 60624                                312-265-7392Objectives:     (Grades 6-8)1. To create a density column from household liquid solutions.2. To calculate the density of an object.3. To determine why objects will float or sink in relation to density.4. To predict the density of unknown solutions.5. To introduce Archimedes' Principle.Materials:The following materials are needed for each group of 3-5 students:        wood (small rectangular or        baby bottle or olive jar          square shape)               graduated cylinder    metal screw or nut                balance scale    plastic (small rectangular or     ruler (metric)           square shape)              large plastic container    corn oil                                or small aquarium    corn syrup                        paper or plastic cups    food coloring (for water)         small piece of rubber             glycerin                          aluminum foil                                         Strategy:                  Instructors Preparations and Student Activities:1. The individual student stations should be set up before students arrive.  Put    several drops of food coloring into the aquarium.  Use different colors for    each group with matching cups.  (optional) 2. Each station or group will have the unknown household solutions within the    cups.  Students are given the information in regards to water (density = one    gram/cm3).  Pour the unknown solutions into the baby bottle.  Students will    observe the various columns formed. 3. One should introduce the concept of density using examples and formula,    density = mass/volume.  Review methods of computing volume.  One should    include the water displacement method too.     4. Each group should have an object for which to compute the density.  For    example, a small piece of wood, plastic, metal screw or nut, and rubber    should be used to determine the density. 5. After computing the density, students are to predict whether or not the    objects will sink or float in regards to density.  Water is used as your    medium (1 gram/cm3).  Make a graph and place all predictions of the board. 6. After making predictions, students are to drop the objects into the aquarium    to observe whether or not the objects will sink or float.  Remove objects    from the aquarium and drop the objects into the baby bottles with the unknown    solutions. 7. Knowing the densities of the given objects, students are to predict the    density of the unknown solutions.  Students will make predictions based upon    where within the jar the objects floated.  For example, did the object float    above or below the water?  Would the unknown solution's density be higher or    lower than that of the density of a known object (wood, plastic, metal,    rubber).    8. After making predictions, give students the names and densities of the    unknown solutions.  Students can compare their predictions.  A graph should    be constructed in regards to Mass versus Volume. Supplemental Activities:     To introduce Archimedes' Principle, students will construct a displacement container using a two liter pop bottle.  They should cut the top and construct a spout by cutting the side of the bottle 2cm wide and 6cm to 7cm long.  Students will discover, when objects are put into the water, the water will rise or bedisplaced.  (Use heavy objects to make observations, for example a can of pop with a known mass.)  Archimedes found that the amount of water displaced is equal to the mass of the object.      In addition, Archimedes' Principle can be demonstrated by having students construct a small barge with aluminum foil with measurements about 10 square centimeters.  Have students get as many pennies as possible on their barges.Afterwards, one should explain Archimedes' Principle in relation to why ships float. `