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BUOYANCY -------------------------------------------------------------------------------- Objectives: Upon completion of this lesson students will be able to: 1. Predict and observe the behavior of regular and diet soft drink cans when immersed in water. 2. Calculate the density of solutions using mass-volume data. 3. Design and construct a neutrally buoyant vessel. 4. Relate density to neutral buoyancy. Materials: Balance Aquarium or other large, deep, straight-sided container filled with water One sealed can each of regular and diet soda (same brand) at room temperature (Coke and Diet Coke and Seven-Up and Diet 7-Up are recommended. Some other brands may not exhibit significant differences between regular and diet versions.) One empty can of each type of soda Paper towels Pencils and paper for student data tables Ice (optional) Plastic foam (cups, blocks, strips or poly puff "packing worms") Finishing nails or metal washers, several sizes Tape, preferably water resistant Scissors Procedure: A. Fully immerse the can of regular soda in water (it should sink and stay sunk), then the can of diet soda (it should rise to the surface and float). B. Distribute plastic foam and nails or washers: 1. Set up data table for recording mass, volume, and density. 2. Determine the mass of an empty, dry, regular drink can and a diet drink can. Determine the mass of a full, unopened can of each solution and record. Read the volume of solution from the side of each can. Record this information in your data table. 3. Determine the overall volume of your unopened cans by water displacement. How do these volumes compare with the volume of the contents indicated on the side of the cans? 4. Calculate the density of the unopened cans by dividing the mass by the volume of each can. (M/V=D) 5. Modify your cans to make them hover in the middle of the container of water. Use plastic foam materials and metal nails or washers to raise or lower the cans. 6. How do the densities of the regular and diet drink solutions compare to the density of water, which is 1 g/mL? Results: Unopened regular soda cans sink, unopened diet soda cans float. Conclusion: Regular soft drinks are sweetened with dissolved sugar and/or high-fructose corn syrup. A great quantity of this relatively heavy substance is required to sweeten regular soft drinks. The artificial sweeteners in so-called diet drinks are many times sweeter than sugar and so they are required in smaller quantities. Therefore, regular soft drinks are more dense than water, and diet drinks are less dense, leading to the regular soft drink sinking, while the diet soft drink floats.