Density Phenomena - Using the concept of density

Bahner, Stan                         Whitney Young High School
6137 N. Maplewood Ave.               997-3739
Chicago, Il. 60659
973-6880

Objectives: (In the words of the student)

I will use the term density to explain three applications of density 
presented by the teacher.

Apparatus Needed

 1. To make cartesian diver:  plastic pop bottle, dropper pipette
     Fill the bottle almost full of water. Fill the dropper pipette 
     about 1/3 full of water and drop it into the bottle. (If the 
     dropper sinks you have too much water in it. You'll have to try 
     again.) Screw the cap tight on the bottle.  Squeeze the bottle 
     firmly and the dropper should dive to the bottom. Release the 
     pressure and it should rise to the top. (If it won't dive, it 
     doesn't have enough water in it.  You'll have to try it again.)
 2. To make density column: Aunt Jemima Pancake Syrup, Revlon Balsam 
     shampoo, Prestone antifreeze, Dawn dishwashing liquid, water 
     colored with food coloring, paint thinner for oil base paint, a 
     jar or graduated cylinder. Carefully pour the liquids down the 
     side of the jar in the order listed.  It makes a pretty density 
     column. DO NOT SHAKE. It will stay nice for a few days if it is 
     not handled. 
 3. To make candle trough: two 6x30 inch pieces of styrofoam art board, 
     paneling scraps, thin plywood, or such material.  Four short 
     candles (one inch or less). Attach the two pieces together to make 
     a V-shaped trough. Raise one end about 12 inches using a ring 
     stand, etc. Place candles evenly along the bottom of the trough.  
     When carbon dioxide is poured down the trough from the upper end 
     the candles will go out in succession. 
 4. To make carbon dioxide to use with candle trough:
       a) dry ice 
     OR ELSE 
       b) cut off 2L pop bottle (or 1000 ml beaker if available)
           vinegar
           sodium bicarbonate
     OR ELSE
       c) Alka-seltzer tablets (at least 6)
 5. To make wave bottle: plastic pop bottle, paint thinner for oil 
     paint (get the low odor kind available from Ace hardware store)
     alcohol solvent (also available from Ace.  It's used as fuel for 
     stoves or as shellac thinner), blue food coloring. Fill the 
     bottle half way with the alcohol solvent.  Fill it the rest of 
     the way with the oil paint thinner.  Drop in about 10 drops of 
     blue food coloring which will sink to the bottom layer and make 
     it blue.  Cap the bottle tightly and turn it horizontal.  It 
     makes entertaining waves.
 6. To make an inverse wave bottle get Carbo-chlor solvent (also at Ace) 
     to form the bottom layer and use water and blue food coloring 
     for the top layer.  Put this one out a week or so after your 
     students have gotten used to the first wave bottle.  Don't say 
     anything. Let them ask the questions.
 7. To make U-tube density trick: glass U-shaped tube or else clear 
     plastic tubing, mineral oil or paint thinner for oil paint 
     (You may also want a 4 foot long piece of clear plastic tubing 
     from the hardware store to help get the point of this across.)
     Pour water down one side of the U-tube and clear oil down the 
     other.  The levels will not be the same.  If the students know 
     that water seeks its own level, this will puzzle them. If not, 
     you can use a clear flexible tube (half inch Tygon tubing works 
     well) filled with colored water to show students that when you 
     raise one end of the tube the water level stays the same on both 
     sides. 
 8. To show convection currents in water: aquarium or such container 
     with clear flat sides, small bottle such as eye dropper bottle, 
     food coloring, hot water (from coffee pot works well and is often 
     convenient).  Fill the aquarium with cool water. Fill a small 
     bottle with hot water and a few drops of food coloring. Hold the 
     bottle shut with your thumb.  Put a small piece of thick paper 
     between your thumb and the hot water for comfort. Place the bottle 
     on the bottom of the aquarium and move your thumb away.  The hot 
     colored water will rise like smoke out of a chimney and form a 
     diffuse layer along the top.  Relate to hot air balloons. 
 9. To make floating balloons: helium tank, balloons 
     Fill ten balloons with different amounts of helium ranging evenly 
     from "almost none" to "ready to burst". Some of the balloons will 
     sink in air, some float.

ALSO USEFUL WITH THIS LESSON IF AVAILABLE
10. A 1960's type Lava Lamp which is available from Simplex 
    International, Chicago for about $40.
11. A trickle-down timer which is available from American Science 
    Center, Northwest Highway, Chicago for about $4.

Recommended Strategies
Present the above as teacher demonstrations.  Have students take notes. 
Have students choose three to write-up using the term "density" 
correctly to explain the observations.