About The Dancing Raisins Experiment:
Raisins may be dehydrated grapes, but when you add a little liquid to them they don’t become grapes again--they become hip-hoppin’ dancers. Of course, if you want to show your child how raisins can get their groove on, you can’t use just any liquid.
That’s because in order to truly show your child the principles of density and buoyancy, you’ll need a little carbon dioxide gas to get those raisins dancing. There are a couple of different ways you can get that effect--with the old standard of baking soda and vinegar or with a less messy (and less predictable) clear, carbonated soda.
Materials You Will Need:
- 2 to 3 clear glasses (depending on how many versions of the experiment you want to run at the same time)
- A box of raisins
- Clear, well-carbonated soda (tonic water, club soda and Sprite all work well)
- Baking soda, vinegar and water
- dance music
Ask your child the following question and have him record his answer on a piece of paper: What do you think happens when you put raisins in soda?
Note: For the baking soda and vinegar version of the experiment, you’ll need to fill the glass halfway with water. Add 1 tablespoon of baking soda, stirring to make sure it dissolves completely. Add enough vinegar to make the glass about three-quarters full, then proceed to Step 4.
- Decide whether you want to use soda or baking soda and vinegar to conduct the experiment or if you want to compare what happens in both versions of the experiment.
- Put out one clear glass for every different type of soda you’ll be testing. Make sure your soda hasn’t gone flat and then fill each glass to the halfway mark.
- Plop a couple of raisins into each glass. Don’t be alarmed if they sink to the bottom--that’s supposed to happen.
- Turn on some dance music and observe the raisins. Soon they should begin dancing their way to the top of the glass.
Observations to Make /Questions to Ask:
What’s Going On:
As you and your child observed the raisins, you should have noticed that they initially sank to the bottom of the glass. That’s due to their density, but because raisins have a rough, dented surface, they are filled with air pockets. These air pockets attract the carbon dioxide gas in the liquid, creating the little bubbles you should have observed on the surface of the raisins.
The carbon dioxide bubbles increase the volume of each raisin without raising its mass. When the volume increases and the mass does not, the density of the raisin is lowered, allowing it to be pushed upward by the surrounding fluid, which now has a higher density than the raisin.
These bubbles increase the volume of the raisin substantially, but contribute very little to its mass. With a greater volume, the raisin displaces more fluid, which then applies more buoyant force, pushing the raisins upwards. (This is Archimedes’ Principle at work).
At the surface, the carbon dioxide bubbles pop and the raisins’ density changes again. That’s why they sink again. The whole process is repeated, making it look as though the raisins are dancing.
Extend the Learning:
Try putting the raisins in a jar that has a replaceable lid or directly into a bottle of soda. What happens to the raisins when you put the lid or cap back on? What happens when you take it back off?