Misconceptions part 2: The Baking Soda / Vinegar Volcano

Ask my teacher friends.  I really hate the baking soda vinegar volcano.

The danger in using vinegar/baking soda to teach about volcanoes is that many students get the wrong ‘take away’ message, unless it is extremely carefully presented. At best (as far as it relates to volcanoes), it shows that a fluid flows downhill. Volcanoes do not erupt because of a chemical reaction, and they do not ‘flow like water’ over a landscape. In my opinion, putting baking soda and vinegar in any container to say anything about volcanoes is, at best, misleading to students. At its worst, it ultimately undermines a student’s confidence in science when they find out they learned the wrong thing from this very memorable demo.

Here’s a video showing a very well executed demo of the vinegar/baking soda volcano.

You’ll notice that in her discussion at the end, its all about the chemistry. It has absolutely nothing to do with volcanos. However, in years of asking college students what they know about volcanos or igneous rocks, I’ve gotten responses full of misinformation based on a teacher giving this demo with baking soda and vinegar. Every. Single. Time.

So, what do we do if we want to be better science teachers?  How do we avoid the pitfalls of the baking soda vinegar volcano?  Can we use this demo for good?  And how should we model volcanoes?

If you want to use the vinegar/baking soda reaction, do it in a bottle with a balloon to discuss chemical changes, to discuss the production of a gas, attach a tube to a closed system and measure the gas produced – it still gives you the same reaction, the same ‘messiness’ – but leaves students with accurate take-away messages.

I really like the wax under sand demonstration. It lives kids with good, accurate images in their minds about fluids moving through different materials. That demonstration has never led to a heated discussion with a student. The vinegar/baking soda demonstration has led to so many problems in my life, and then (maybe what’s worse) those are the students who hate science in college and adulthood – because they reached a point where they questioned everything they thought they knew about science – because that one messy lab where their teacher taught about volcanos is the one thing they remember about science. And its not true.

Here is a lesson I advised a colleague of mine (Kelly) with, and it is ‘accurate’ in its portrayals of the reasons that volcanoes erupt. It also uses a model that is built based on trying to reproduce the same effects (pressure) that cause a volcano to erupt, but in a classroom safe way (air pressure rather than pressure produced by heated magma).

For those of you following along who haven’t seen it: the wax volcano. 

3 thoughts on “Misconceptions part 2: The Baking Soda / Vinegar Volcano

  1. Great blog post! I teach HS Earth science and have never used the baking soda / vinegar example… but I’m intrigued with the wax example. Volcanoes / plate tectonics is my favourite unit to teach… and I love finding new ideas to incorporate into my class.

    I use bottles of corn syrup (shield volcanoes) and hair gel (strata) to show students between the mafic and felsic magmas… it works well.

    Thanks,
    Addie
    Addie Education – Teacher Talk

  2. Thank you so much! My whole family knows better than to call the vinegar/baking soda reaction a “volcano” lest I go into a tirade! I almost stopped watching Lost a few years ago when they used the demo in one of their scenes and a kid said “Is that how our volcano works?” and the teacher said “yes!” AAAK!

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