Alka Seltzer Rockets

What you need:

  • Alka seltzer tablet
  • Water
  • Film canister
  • Stickers
  • Paper template
  • Tape

What you will do:

  1. Cut out the fins, body, and cone for your rocket. Use the template provided.
  2. Turn the film canister upside down with the opening on the floor. Tape the body around the film canister. Tape the cone on the bottom (side that does not open). Tape the fins onto the rocket on two sides.
  3. We recommend going outside to launch your rocket!
  4. Fill your film canister up with water about ¼-1/3 of the way.
  5. Drop ½ a tablet of Alka-Seltzer and snap the lid on tight.
  6. Quickly place the rocket upright (lid on the ground) and stand back. CAUTION: Be careful when launching your rocket. Stand back and don’t point it at anyone!
  7. Discussion questions and additional experiments:
    • a. Time how long it takes your rocket to return to Earth.
    • b. What happens to the rocket if you use more or less water?
    • c. What happens if you use hot water vs. cold water?

What’s happening? Why does your rocket go up?

  • When you mix the Alka-Seltzer tablets with water, a chemical reaction takes place between the citric acid and sodium bicarbonate contained in the tablet and the water.
  • This chemical reaction creates many bubbles of carbon dioxide gas. When you combine this chemical reaction with a film canister, it pops, and it goes up!
  • It goes up because gas is building and building in the closed film canister and since the lid is the weakest point of the canister, the lid pops off and all that gas comes rushing out of the end of the canister.
  • This action can be explained using Newton’s Laws of Motion, more specifically it is an example of Newton’s Third Law of Motion – “Every action has an equal and opposite reaction”. The gas rushing out of one end of the canister (the action) causes your rocket to move in the opposite direction (the reaction).
  • This is exactly how all rockets work whether you use an effervescing tablet as your fuel or a chemical rocket propellant like they do at NASA.

Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. Extension programs are available to all without discrimination.