Blogger Amy Koester

Geyser Science for the School-Age Crowd

Explosions are almost always a hit with the school-age crowd. When my library offered a Volcano Science program last year, the excitement in the room was palpable as we erupted individual volcanoes; there’s just something about witnessing a destructive force that connects with kids. If that’s what it takes to get school-age library visitors interested in STEAM concepts, well, hook me up with the (child-safe) explosives. Geyser Science is just the thing.

Photo by Amy Koester
Photo by Amy Koester

First, we talked about the science. I had planned to use some terrific geyser resources from the National Park Service, but my program took place during the government shutdown and so these resources were largely inaccessible. Luckily, one Park Service video was still on YouTube. After watching the video, I pulled out a paper model of a geyser that I had made. Using the pieces of the model, we talked about the geological processes that create a geyser and its eruptions. We spent a few minutes on questions and fun facts shared by kids who had visited Old Faithful at Yellowstone National Park.

Next, we explored the science behind geysers through a series of hands-on activities. One of the main scientific elements in geysers is pressure, so our experiments largely focused on how pressure works and its affects on objects.

  • Pressure of water in a bottle – This activity required a tub, a clear 2-liter bottle with the label removed, a thumb tack, a funnel, and a pitcher of water. I used the thumb tack to poke a small hole in the 2-liter bottle. With the children watching, I removed the thumb tack from the bottle and poured water from the pitcher directly into the bottle. When the water level in the bottle rose above the small hole, a slight trickle of water escaped the bottle into the tub. We next placed the funnel atop the bottle, then quickly poured more water through the funnel. This time, the water escaped through the hole in a shooting stream. We talked about how the funnel wouldn’t let any air escape while the water entered the bottle, causing pressure to build and push more water out through the tiny hole.
  • “Breathing” balloon – This activity used an empty plastic water bottle and a balloon. After placing the balloon completely over the opening of the bottle, kids took turn squeezing the bottle and causing the balloon to stand straight. This activity demonstrated that, when the bottle was squeezed, the pressure caused the air in the bottle to move to the only available space: an expandable balloon.
  • Blowing up a balloon in an enclosed space – This activity used two empty plastic water bottles, two balloons, and scissors. This time, the balloons were placed completely over the bottles’ openings with the balloon oriented inside the bottle. One plastic bottle had a hole cut out of it, and the other was pristine. First, I had a child try to blow up the balloon in the bottle with a hole; the child had no problem doing so. Then, I had another child attempt to blow up the balloon in the pristine bottle. Too difficult! (I prepped a few extra no-hole bottles so multiple children could try blowing up the balloons, all to no avail.) We talked about displacement and how, without something like a hole through which air could escape, more air couldn’t easily be added to an enclosed space.
  • Paper bag explosions – We moved outside for this and the next activity, which required paper lunch bags and baking soda (or flour, or cornstarch, etc.). I put a bit of baking soda in each child’s bag, and I demonstrated how to blow up the bag like a balloon. The children next popped their bags and observed what happened to the baking soda. Because the force that causes the bag to pop pushes against the air in the bag, the explosion causes the bag’s contents (air and baking soda) to fly from the explosion in all directions.
  • Mentos & Diet Coke geysers – This activity requires a 2-liter of Diet Coke, a sleeve of Mentos mints, and a safety zone around the blast radius. It is a demonstration of how a chemical reaction can cause a buildup of pressure, and it’s a magnificent demonstration at that. Carefully drop all the Mentos into the Diet Coke bottle and watch a huge geyser spray out. Cheers usually abound.
Photo by Amy Koester
Photo by Amy Koester

We ended with science in action as we created and tested our own geysers. We were back inside for this final series of activities, and each child had a filled water bottle, several tablets of Alka-Seltzer, and space over a tub to catch splash. I first demonstrated an Alka-Seltzer geyser eruption by crushing up two tablets, quickly dumping them into a water bottle, and holding my hand completely over the bottle’s opening to allow pressure to build up. After counting to five, I moved my hand and a modest geyser explosion occurred. From there, the children experimented with geysers on their own. They used as variables the size of the bottle, the number of Alka-Seltzer tablets, and the length of time of pressure buildup to try to determine what combination of factors creates the most impressive geysers. We even have a child put her crushed Alka-Seltzer tablets in a balloon, cover the mouth of the bottle with the balloon, and then allow the Alka-Seltzer to fall into the water to see if the balloon would expand (it did, slightly). The children drew their own conclusions about making their own geysers before the program room turned into a bit of a splash zone, at which point I wrapped things up.

There were a variety of geyser and pressure resources, both books and DVDs, available for the attendees to check out. What I most enjoyed about the end of the program was hearing the children’s plans for continuing their optimum-geyser experiments at home. Any time a library program inspires interest and a desire to pursue a topic further, I consider it a success.

What sorts of eruptions have you hosted in your library in the name of science?


  1. Sarah West

    Thank you for sharing! We have not done a lot of science recently as our main science guru has retired but we are getting back in to it for 2014. So a few questions – What age were the kids for your program? How many attended? How many staff did you have? Were parents present?

    1. Amy Koester

      Sarah, I advertise my school-age science programs for children in kindergarten through fifth grade. I usually have between 10 and 20 children attend, with the bulk in grades 1-3. I am the only staff person in these events, although many parents do attend with their kids and are happy to lend a hand as needed.

      Let me know if you have any more questions or if I can support you as you get back into science programming!

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