Today Richard read in his new element books about sodium and potassium. He was very interested in chemical reactions involving them so I flipped through a book and found a couple demonstrations involving baking soda (sodium bicarbonate) and vinegar. Mixing baking soda with vinegar creates carbon dioxide bubbles. You can do lots of fun things with this.
The first involved filling a jar half full of water the adding 4T of baking soda and 3T of vinegar. Finally, drop in 10 raisins and see what happens to them. The directions have you adding the baking soda after the vinegar. This didn’t work very well. The soda didn’t dissolve fully so the raisins got stuck in it at the bottom. The second time we mixed the soda with the water first until it was dissolved then added the vinegar. That worked much better.
Surprisingly, it was Karen who first figured out what was happening and why. The reaction caused bubbles which stuck to the raisins. They then float the raisin to the top where the bubbles burst causing the raisin to sink. Then more bubbles stick, the raisin rises and falls again. This continues until the reaction no longer is creating large bubbles.
The second thing we did is the classic volcano. However, we didn’t make the mountain. First pour 1/2 cup vinegar in a 2L bottle. Then add 1/3 cup dish soap. We had 2 kinds of dish soap. One was blue, the other yellow. So we played with different combinations of the colors as I filled the measuring cup to make different shades of green. (you’re supposed to add red food coloring, but our “lava” was dark green at this point so we just left that out) Then we taped the bottle to cardboard and took it into the bathtub. Drop in a toilet paper packet containing 1T baking soda and watch the bubbles rise. Believe it or not, I’d never done this before. The kids played with corking the bottle top and the bubbles coming out a small hole in the side.
These experiments didn’t work especially well for us. Our vinegar is too old. I’d like to do them again with new vinegar. Still, they worked well enough for the kids to get the idea of what’s happening and we had a lot of fun. Not only did we learn about chemical reactions, but also color mixing, math (fractions, counting, and measuring), and geology.