Mixtures II: Vinegar and Baking Soda


In front of each child, I put a cup with the vinegar on top of a paper towel. Then I asked them to make observations about what was in the cup.

Q: What does it look like? What does it sound like? What does it smell like?
A: It looks and sounds like water. It smells yucky, like oil (sometimes it is mixed with oil and put on salads), like stinky socks (maybe your socks!)…

I told them that it was vinegar. Most had never heard the word. I really wanted to tell them what vingar was, but I didn’t know, so I settled for reading the ingredients. I talked about some uses of vinegar and we had a great discussion of pickles and what people did before they had refridgerators.

Then we passed out the cups of baking soda, and told them to wait until everyone had one, and on the count of three they could pour all the baking soda into the vinegar. Wow!

We got them to talk about what happened. Some cups overflowed. There were bubbles. What’s in a bubble? We talked about the difference between solid, liquid and gas. (I wish I had known better definitions of these, but we muddled through it.)

Next we did another experiment that I told them I had never tried before. I put vinegar in the bottle and baking soda in the balloon, then fastened the balloon over the mouth of the bottle and mixed the two. The balloon inflated about half way and the kids were wildly impressed. Everyone wanted to feel the balloon. We repeated the experiment with more baking soda and more vinegar and saw the ballon inflate even more.

We had just enough time (and baking soda and vinegar) to let everyone mix them again themselves. We didn’t measure so precisely this time, so there were more overflows, but that just added to the fun.

Materials (for a class of 20):
12 gallon vinegar
2 boxes of baking soda
40 plastic cups
1 empty water bottle
1 baloon

For each student,
- 2 Tbsp. baking soda in one cup
- 4 Tbsp. vinegar in another cup
I tested this in advance to see that when mixed the bubbles filled the cup, but didn’t overflow.

inspired by Magic Potion Science