Density Phenomena - Using the concept of density
Return to Chemistry Index
Bahner, Stan Whitney Young High School
Objectives: (In the words of the student)
I will use the term density to explain three applications of density
presented by the teacher.
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
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
b) cut off 2L pop bottle (or 1000 ml beaker if available)
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
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.
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.