Being lazy and having a new baby (who at the time was content), I didn't want to spend time looking up the experiment online. We decided to experiment on our own on how much baking soda vs. how much vinegar and the size of the container we were using for the experiment.
Mountainous material for the volcano:
I admit again that I am lazy. J had been given a lot of Play-Doh for a birthday last year, so I'd figure we'd use some up by covering the paper cup in different shades of Play-Doh. I don't want to be crafty at this point in my life, but here is a homemade playdough recipe if you'd like (painted paper mache volcano might be better if you have time to plan ahead and want it to look cool). The Play-Doh got soggy, but held up. We tossed it after we were done though we were thinking of saving it before we started, which is why we only put a small amount of orange and red on our volcano. We remained lazy and just used the Play-Doh container, without any decoration, to test a smaller container. J enjoyed it just as much as the decorated volcano since the "wow" factor is in the interaction between the baking soda and vinegar.
Place volcano in a pan with high sides, or you'll have quite a mess to clean up afterwards.
Amount of baking soda:
We used 1 tablespoon (tbsp) of baking soda as a starting point. We also used 2 tbsp, but 1 was enough to give multiple eruptions with our amount of vinegar, see note below on limiting reagents. We placed the baking soda in the cup first.
Note: We started with about 1/2 of a box of leftover old baking soda from the last time we switched it in the fridge, so there was plenty to experiment with.
Amount of vinegar:
We had a little under 1/2 gallon of vinegar to experiment with though we initially weren't planning to use it all. An adult poured it into a small 8 oz cup for J to handle. You definitely don't need a 1/2 gallon of vinegar, but we buy it by the gallon because it's cheaper and we can use it in impromptu experiments.
Size of container:
It turns out that if you have limited resources (ie. minimal amounts of mountainous materials, baking soda, or vinegar), go with a smaller container. If not, the bigger container works just fine.
Let your little one lead. We let J measure the baking soda and gave him the vinegar in a kid size cup. He knew what to do from other baking soda/vinegar experiments. I thought the reaction was over after the first pass of vinegar. J's curiosity lead to the discovery that 1 tbsp of baking soda can lead to multiple "eruptions" (reactions).
With 1 tbsp of baking soda, the unmeasured vinegar (under 8 oz) poured in spurts seemed to be the limiting reagent. We poured more vinegar, and the reaction kept going. This is an advance concept for preschoolers, but you can definitely point it out and see if they follow.
After experiment free play:
I'm big on letting my 5 year old continue to play once the experiment is over. This experiment resulted in a sensory bin since there was a big glup of baking soda in basically water. However, when he transferred his pile of baking soda from one part of the tray too another, he got a sizzle. There was still a reaction left!
And apologies for the shaking camera. I was helping J with the experiment, and John was juggling the camera and this cute nugget:
She liked the volcanoes too. Well, at least she didn't fuss.
Have you experimented with baking soda and vinegar volcanoes? How did you model the volcano?