Popping Test Tube

Popping Test Tube

How many times can you make the stopper pop from the test tube?

Suitable for kids aged 7+, with adult supervision


  • The plastic stopper in the test tube is a projectile and must be aimed away from people and faces.
  • The alka seltzer tablet is a medicine. DO NOT EAT. Seek medical advice if ingested by a child.
You Need:
What to do:
  1. 1/4 fill the test tube with tap water.
  2. Break an alka seltzer tablet into pieces and put about 1/4 into the test tube of water.
  3. Push the stopper into the top of the tube. You can either hold the tube or leave it standing on a flat surface. Either way, keep your face away from it.
  4. Wait for the stopper to pop off (this could take up to 30 seconds or more so be patient). Shaking the tube speeds up the reaction.
  5. Put the stopper back in place after the first pop. Will it pop again?
  6. Try different amounts of water for the best popping. Or try mixing baking soda, vinegar and detergent in the tube instead. What difference does this mix make to the pops? Citric acid, baking soda and water also works.

Why is it so?

Just like in the super-cold bag experiment, adding these combinations of chemicals makes a chemical reaction that produces a new chemical, carbon dioxide gas. A build up of gas in the tube builds pressure, enough to eventually pop the stopper from the tube. You should judge which works the best by your experimentation.

Test tubes with rubber stoppers are available from the science supply section of this website.