Thursday, December 19, 2013

Cartesian Divers

For my 4th graders {who are studying matter}, I let them make Cartesian Divers. 

OH. EM. GEE, ya'll. I never imagined that this simple little activity would be such a hit! One of my teacher-friends has a 4th grader at our school and she told me that not only did her daughter go home and basically teach my entire lesson to her dad {yay!!}, but she also brought her Cartesian Diver back to school the next day because she was so excited about it.

It is THE simplest thing to make, THE simplest lesson to teach {assuming you've already gone over density and buoyancy}, and the kids L-O-V-E it! I mean, seriously. What else can you ask for?!

This is it. Really.
About 2-3 months ago, I asked my 4th graders to start saving 2 liter pop bottles. The Steve Spangler video I was modeling this after did it with a 1-liter bottle, but I knew it would be easier to collect 2-liters, so we went with that. Anyway.

I showed my students this short Steve Spangler clip to let them know what was about to happen:

Seriously -- every time I showed the intro video, the class let out a "whoooaaaa!!" I was awe-struck. Who would've thought that such a simple activity would have them so engaged?!

After the intro video, we talked about how and why this Cartesian Diver worked. They wrote a little in their notebook, and then they got to create.

  1. Tear any labels off a 2-liter bottle. Make sure it's free of any soda. 
  2. Cut a pipette to about 1/4 of an inch. 
  3. Force a hex nut onto the end of the pipette. {It will fit over the skinny part but will need to be forced onto the "lip" part, as I call it.}
  4. Fill the pipette -- the diver -- with about 25% water. Test it in the cup of water to make sure it just barely floats. 
  5. Fill the liter bottle with water. Drop the diver {pipette} inside and make sure it just barely floats.
  6. Fill the liter bottle up until it has ZERO air inside anymore. 
  7. Screw the cap on.
  8. Squeeze the bottle in the middle as hard as you can. The pipette/diver should "dive" down to the bottom of the bottle!
  9. Use the Sharpies to decorate the bottle {and the diver, if you feel so inclined}
This is definitely an activity I will keep!

Here's a video of a project where the kiddo made the pipette into a scuba diver who was searching for gold... so creative!


I definitely recommend this lesson!


  1. Seems like an awesome activity. Glad it went over so well!

    FYI I’m having a giveaway at my blog for my 32-pg place value book--if there are enough entries everyone will be a winner! Feel free to share about it and enter.

    Lucy Kids Math Teacher


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