An activity adapted from an activity supplied by Kim Giesting of Connersville, IN.
Type of Lesson: Experiment/Discussion
Time Needed: 20 minutes - 1 class period for variations
MEGOSE PME17 Describe and compare objects in terms of mass, volume, and density.
Quick Summary of Lesson
This is a mini-experiment that can be used to start a discussion on density.
7-up (or other clear, carbonated drink)
1. Have students hypothesize what will happen if raisins are added to the liquid.
2. Add raisins.
3. Have students observe what happens.
4. Discuss why this occurs.
Notes to the Teacher
The ability to regulate buoyancy, or the ability to rise when submerged, is critical to the safety of surfers, swimmers, deep-sea divers, submarines, and countless forms of marine life. In this activity, you saw that when the raisins sink to the bottom of the glass, bubbles being to cling to their sides. The raisins then rise upward through the liquid. When they reach the surface, the bubbles pop or break away and the raisins spin over and sink to the bottom of the glass again. Then more bubbles cling to their sides and the raisins repeat their ascent! The raisins sink because their density is greater than the density of the liquid. The gas bubbles in the liquid act like tiny balloons clinging to the sides of the raisins. The gas bubbles plus the raisins are less dense than the liquid, so the raisins rise to the top of the glass. When the raisins lose the bubbles at the surface, their density becomes greater than the density of the water once again and they fall.
I have heard several variations to this demonstration. In fact any of these variations could be the subject of study for one class period. Is there a limit to the number of raisins that can be put in the container so that they all ascend and descend? What happens if the liquid is heated? Does coke or root beer change things? How could you get the raisins to ascend more quickly? What other objects would dive for you? etc, etc.
Need More Information? Try Using Windows to the Universe
Please use these links for further ideas or more information:
Density of the Earth
Density inside the Sun
Energy density inside tornadoes
Another activity for the classroom called Floating Golf Ball
Last modified prior to September, 2000 by the Windows Team
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