You’ll learn about the key ingredient in an explosive eruption like the one we’re simulating in lab today.


[am4show have=’p8;p9;p30;p57;p79;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:


  • test tube
  • rubber stopper
  • toilet paper
  • goggles
  • distilled white vinegar
  • baking soda powder
  • measuring tape
  • scale that weighs in grams
  • ruler


 


Download worksheet and exercises


Active volcanoes create domes inside the eruption chamber which act like giant plugs, stopping up the magma and building up pressure until … BOOM! The dome explodes and out comes all the material from inside, just like the plug in the test tube.


Baking soda (sodium bicarbonate) and vinegar (acetic acid) chemically react and combine to form carbon dioxide bubbles and a solid form of sodium acetate, which looks like little white flakes at the bottom of the solution.


For baking soda and vinegar, the chemical equation for the reaction looks like this:


NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2


The chemical reaction actually occurs in two steps. The first reaction looks like this as the vinegar reacts with the baking soda to form sodium acetate and carbonic acid:


NaHCO3 + HC2H3O2 → NaC2H3O2 + H2CO3


But the carbonic acid isn’t a stable molecule, so it breaks down to make the carbon dioxide gas like this:


H2CO3 → H2O + CO2


Since the bubbles are heavier than air, the carbon dioxide builds up and overflows, and stays in the test tube until you dump it out.


  1. Put on your safety goggles. NO EXCEPTIONS!
  2. Tear off a single sheet of toilet paper.
  3. Pour a small pile of baking soda right in the middle of the toilet paper.
  4. Fold the toilet paper in half, and then wrap the sides around until you make a mini-burrito or mini-plug. You want it to fit snugly into your test tube (but don’t put it in there yet!)
  5. Carefully pour vinegar into your test tube. You want about an inch (2-3 cm) of vinegar.
  6. Gently push the toilet paper burrito plug into the test tube, but don’t let it touch the vinegar yet.
  7. Push in your rubber stopper, making sure it’s nice and snug.
  8. Point the stopper away from you or anyone else … like straight up.
  9. Place a thumb on the stopper and shake the tube several times. Remove your thumb before the stopper pops!
  10. After you’ve tried this a few times, it’s time to start taking real measurements. Here’s what you do:
  11. Place the sheet of toilet paper on the scale and zero it (hit “tare”).
  12. Add baking soda and record the mass of the baking soda (in grams) on your data table.
  13. Fill your test tube with vinegar. Rest the bottom of the test tube on the table, and using a ruler, measure many centimeters of vinegar you added and record this number on your data table.
  14. Roll up the toilet paper into the burrito plug and insert it into the test tube.
  15. Add the stopper and shake!
  16. Measure the distance that your stopper traveled in your data sheet and repeat the experiment until you’ve found the perfect ratio of baking soda and vinegar to make the stopper fly the farthest.

Exercises


  1. Does the stopper go further when you add more or less vinegar?
  2. Look at your answer for #1 above. Why is that?
  3. Which gases are produced by this reaction?

[/am4show]


Have a question ?

Tell us what you're thinking...

Comments

6 Responses to “Test Tube Cannon”

  1. Aurora Lipper says:

    So glad you and your daughter enjoyed this experiment! Yes, your daughter’s explanation sounds right to me.

  2. rhall6187 says:

    Hi Aurora!
    We just did the test tube cannon experiment. It was so cool. I had my daughter put different volumes of vinegar in each tube 1 ml, 2 ml, and 3 ml. I said to make the prediction of which one would go the farthest. She said the one with the least amount of vinegar. I thought the one with the most vinegar (we used equal amounts of baking soda) would go the farthest, but it was the one with the least. When I asked her why she thought the one with the least, she said that it had more space to produce more gas (elementary Wilson). I was secretly bemused since I was the one who was a chemistry major in college. Go figure ;-), stumped by an eighth grader. But anyway, was her thought process correct?

  3. When you read through the steps under the video, you can see how the ruler is used to make measurements of how much reactants you are adding to your experiment. For most kids, they just want to do the experiment and enjoy the process. However, if you need more details on how to make a data log and take real data, then you’ll use the rest of the equipment and read through the instructions carefully.

  4. Michelle Stevens says:

    What I was going to say was, what were the ruler, measuring tape, and scale for? They weren’t used in the video. I also noticed that in the beginning of the video, it showed a picture of the basic hovercraft. Anyway, I tried this experiment and it flew probably 15 feet or so in the air! 🙂

  5. This one is carbon dioxide, just like the soda pop idea you had. 🙂

  6. Anonymous says:

    We were thinking this is kind of like a soda pop when you shake it and it runs all over. Which type of gas does that produce to make it explode like that?