Dancing Raisins Experiment
Carbon dioxide gas dissolved in soft drinks, for example 7-up or Sprite which is responsible for giving them their fizz. You can use the Carbon Dioxide fizz from a soft drink to make raisins dance.
For this experiment you will need:
- A can of colorless soda (e.g., 7-Up or Sprite)
- A tall, clear glass or plastic cup
- Several raisins (fresh raisins work the best)
Pour the can of soda into the tall glass. Notice the bubbles coming up from the bottom of the glass. The bubbles are carbon dioxide gas released from the liquid.
Drop 6 or 7 raisins into the glass. Watch the raisins for a few seconds. Describe what is happening to the raisins. Do they sink or float? Keep watching; what happens in the next several minutes?
Raisins are denser than the liquid in the soda, so initially they sink to the bottom of the glass. The carbonated soft drink releases carbon dioxide bubbles. When these bubbles stick to the rough surface of a raisin, the raisin is lifted because of the increase in buoyancy. When the raisin reaches the surface, the bubbles pop, and the carbon dioxide gas escapes into the air. This causes the raisin to lose buoyancy and sink. This rising and sinking of the raisins continues until most of the carbon dioxide has escaped, and the soda goes flat. Furthermore, with time the raisin gets soggy and becomes too heavy to rise to the surface.
You might want to try other objects to see if they exhibit this behavior. Any object whose density is just slightly greater than water’s and has a rough surface to which the gas bubbles can attach should be able to dance in the carbonated water.
Another way to do this experiment is to generate the carbon dioxide gas using the reaction of baking soda and vinegar. Fill your glass about 1/2 full with water. Add one teaspoon of baking soda and stir until it is dissolved in the water. Add 6 or 7 raisins to the glass. SLOWLY pour in vinegar until the glass is about 3/4 full. The vinegar and baking soda react to form carbon dioxide bubbles, and the raisins will dance just as in the soft drink!
--Ssmith 07:38, 16 March 2010 (UTC)