Baking Soda Bubbles

Materials

1. 1/4 cup of baking soda  
2. 1 cup of vinegar
3. Bubbles and a bubble wand (you can get this at most toy stores)
4. 2 large, clear containers, like a clear plastic or glass bowl
5. Small clear cup
6. Bowl
7. Spoon

Instructions

1. Put 1/4 cup baking soda in a clear container.
2. Then add 1 cup of vinegar.
3. The mixture of vinegar and baking soda will bubble. It's making carbon dioxide.
4. Blow some bubbles into the container and watch how they float on the carbon dioxide. The bubbles are floating where the carbon dioxide and air meet.

Explanation

1. The carbon dioxide stays at the bottom of the bowl because it is more dense than the air in the bowl. The bubbles float on top of the carbon dioxide because they are filled with air and the air is less dense than the carbon dioxide.
2. This will help explain what density means. Pretend that you had two balloons and you filled one with air, and the other one with the same volume of carbon dioxide. The balloons would be the same size, because the gas in them takes up the same amount of space.
3. But, if you weighed both balloons, the one with the carbon dioxide would be heavier. This means that it's denser than the balloon with air in it.
4. If you still don't understand density, don't worry. There are lots of people out there who can answer your questions. Talk to your teacher, go to a science museum, visit your local library, or ask your parents.