When you put popcorn kernels in water, they sink to the bottom. But with a little kitchen chemistry, we can make them hop to life! Adding vinegar and baking soda to the water creates a chemical reaction that releases bubbles of carbon dioxide (just like bubbles in soda!). When the gas rises up through the water, it carries the kernels with it. Then, when the bubbles pop at the surface, the kernels sink back down to the bottom until they can hitch another ride from some other bubbles.
We chose popcorn kernels because they are dense enough to sink in water, but not so heavy that they can’t be lifted by the bubbles. If you try this with rice, you’ll find it may not work as well — rice grains are too dense and too small to catch onto bubbles. What do you think will happen if you try this with raisins? Here’s a hint: raisins are not particularly dense and they have lots of nooks and crannies for catching bubbles!
Connections with Next Generation Science Standards (NGSS)
Matter and Its Interactions 5-PS1-4
Conduct an investigation to determine whether the mixing of two or more substances results in new substances.
Experiment with acids (vinegar) and bases (baking soda) to create a new substance (carbon dioxide). The popcorn kernels help demonstrate that carbon dioxide is less dense than vinegar and baking soda. The difference in density causes the bubbles to rise up in the mixture.
- One handful of popcorn kernels
- Food coloring
- 2 teaspoons baking soda
- ½ cup of vinegar
- 2 cups of water
- 1 Gather your materials.
- 2 Add 2 cups of water to a Ziploc® brand sandwich bag (avoid filling the bag beyond half its size). You can ask someone else hold the bag upright as you pour in the water.
- 3 Pour in 2 teaspoons of baking soda.
- 4 Drop in some popcorn kernels; they should sink to the bottom of the bag.
- 5 Slowly pour in a ½ cup of vinegar. The mixture will fizz and your grains will begin to float to the top of the bag!
- 6 Add a couple drops of food coloring to the mixture
- 7 Keep watching the kernels and how the bubbles lift them to the surface. Eventually as the chemical reaction slows down, the kernels will stop dancing and hopping. When this happens, you can add more baking soda and vinegar to the same bag and watch the reaction happen all over again! Try experimenting with other items in your pantry. What other materials do you think might hop and dance with a little help from carbon dioxide?