Density Phenomena - Using the concept of density

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. 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.
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