Hi. I’m Rene, a children’s services staff member with the Charlotte Mecklenburg Library. Today I’m going to be sharing an experiment with you that’s called “dancing raisins.” And we’re going to begin by comparing two different liquids that we’ll use in our experiment.
First, we’re going to start with just water. I’m going to pour some into the cup. And what I want you to do is just to observe the characteristics or the properties of water. What are some of the ways that you can tell that this is water in the cup? We know that it’s clear or colorless. It doesn’t seem to have an odor. And we know that if we were to taste it, it doesn’t have much of a flavor.
Now let’s compare that with a clear soda. A carbonated beverage. Notice what happens when I open this bottle. Let’s pour some into the cup. And I want you to notice the difference in the physical properties or characteristics of the soda. Just by looking at what’s in the cup, can you tell that it’s a soda? You see that it’s clear or colorless like the water, but there are lots of bubbles in the solution. Now let’s bring out our raisins. I’m going to add some raisins to the cup of water, and I want you to make a prediction. Do you think the raisins will float or will they sink to the bottom of the cup? Let’s try it out. Was your prediction correct?
Now let’s try the same with the cup of soda. Let’s add some raisins. What’s your prediction? Will they sink, or will they float? Notice what’s happening as we add them to the cup. One of the things that makes the carbonated soda different from the water is all of those fizzy bubbles that you noticed. And those are made up of carbon dioxide. That’s what makes the soda fizzy. When we add the raisins to this cup, unlike the water where they sunk, and they stayed at the bottom, this time those raisins, with their bumpy surface, get covered with carbon dioxide bubbles. And those bubbles, they act like little balloons or little life vests that make the raisins come up to the surface. But when the raisins get to the surface, all of those carbon dioxide bubbles pop, and the raisin doesn’t have anything to help keep it afloat anymore. It actually becomes less buoyant.
Buoyancy is the characteristic that helps something float. All of those little carbon dioxide bubbles help it float to the surface, but when they pop, it goes back down to the bottom. And that’s why we call this experiment dancing raisins.