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Mini Pop Rocket

In this activity, students construct a rocket using a canister with a snap on lid and set it off with an effervescing antacid tablet.

Alka-Seltzer contains citric acid and sodium bicarbonate (baking soda). When you drop the tablet in water, the acid and the baking soda react to produce carbon dioxide gas.

The CO2 gas pushes against the lid of the canister until there is so much pressure that the lid pops off. When the gas explodes downwards, it pushes the rocket in the opposite direction, causing it to go up (Newton’s Law of Motion).

This system of thrust is how a real rocket works, whether it is in outer space or here in the earth's atmosphere. The difference is that real rockets use rocket fuel.

This activity is best done outside or in a large space (like a gym) that is easy to clean. 

Objectives

  • Explore and demonstrate the effects of action and reaction forces.

Materials

  • Per Student:
    1 empty film canister, 1oz playdough, or container with a lid that snaps on tightly
    paper
    scissors
    tape
    1/2 Effervescent antacid tablet (Alka-Seltzer works the best)
    water
    eye protection

Key Questions

  • What makes the pop rocket move?
  • What forces are acting on the canister rocket and in what direction are they acting?
  • Which rockets went the highest, and why?
  • How can you make the rocket go higher?
  • Why does the rocket come back to the ground?

What To Do

Part 1: Building the Rocket

  1. Make the rocket body:
    Tape one side of a piece of paper onto the canister, with the open end of the canister exposed.
    Roll the paper around the canister to create a tube and fasten it with another piece of tape.
    Leave some space between the open end of the canister and your rocket body, so that you can easily open/close the canister.
  2. Add a nose cone and fins as desired:
    Hint: There is no one right way to make a paper rocket. Try a long, skinny rocket or a short, fat rocket. Try a sharp nose cone or a blunt nose cone. Try it with fins or without fins.

Part 2: Launching the Rocket

  1. For safety, go outside. This rocket will fly up very high and very quickly. Don’t forget to put on your eye protection!
  2. Remove the lid and fill the canister 1/4–1/3 full of water.
  3. Get the film canister lid and effervescent antacid tablet ready.

WARNING: the next steps must be done within 5 seconds!

  1. Drop the half tablet into the canister.
  2. Snap on the lid tightly.
  3. Place the rocket on a firm surface with the lid down.
  4. STAND BACK! Watch it fly

Extensions

  • Experiment with different fuel mixtures (add more or less Alka-Seltzer and/or water) and record the results. How much water causes the rocket to fly the highest? What is the ideal size tablet for a certain amount of water?
  • Does water temperature affect how fast the rocket launches?
  • Experiment with different body sizes, construction materials, and cone and fin sizes and shapes to create a different rocket.
  • Add a payload (e.g. toy astronauts) and record what happens.
  • Try replacing the film canister with an alternative such as mini (1 oz) playdough containers, snap-together Easter eggs or non-childproof prescription bottles with snap-on lids (available at pharmacies). Do they perform differently?

Other Resources

Science World Resources | Fusée gazeuse | French version of this resource