Inspired by one of Limerick’s class experiments at our co-op, we spent an afternoon watching baking soda and citric acid react explosively in our kitchen 🙂
One thing I really liked about the way his co-op teacher presented the baking soda/lemon juice reaction was that she asked a lot of questions designed to help the kids come up with hypotheses and logically critique those hypotheses. Each lemon volcano had three components: the lemon, the food coloring (to make it look more like lava!), and the baking soda. So she asked them what they thought made the eruption happen, for example, and when a lot of the kids said the baking soda, she pointed out that the baking soda wasn’t making fizzy bubbles when it was all by itself in the bowl!
So when we replicated and expanded upon the experiment at home (Rowan was so jealous that Limerick got to do it at co-op and he didn’t!), I tried to ask similar leading questions. We also decided to test other citrus fruits with the same reaction, so I had the kids think about the differences between the fruits and guess which would make the biggest reaction beforehand, so we could compare our hypotheses with our results.
To my surprise, the two types of oranges we tested had drastically different results. The big navel orange was even less reactive than I’d expected, while the small juicing orange was almost as explosive as the lemon! The grapefruits were also quite dramatic, being overripe and thus extremely juicy and very fun to squeeze everywhere to create great “lava flows” of fizzy reactive liquid. I do think the lemons were still the most reactive, although the results were not anything like quantitative 😛
While we didn’t draw chemical diagrams and get into the atomic reason acids and bases react, we did have a lot of fun exploring the reaction itself! It’s such an easy and exciting way to see how different types of substances can interact.