We have seen many kids enjoy this project. Not only do they like the loud pop and seeing their rockets go up, they take great pride in building their own rocket.
The rocket can be just for fun or can be a great opportunity to learn / discuss some science.
Check us out at catsscience.com and on Facebook
Step 1: Materials
Effervescent tablet like Alka-Seltzer. Generic works fine.
Typing paper (any paper will do)
Markers, colored pencils, crayons
Something round to trace
Vinegar and baking soda can be substituted for the Alka-Seltzer and water. We just like to use the tablets for ease.
Step 2: Preparing Pieces
Take the paper and wrap in once around the canister. Elephant/giraffe, hotdog/hamburger, tall/short doesn't matter. Mark where the paper overlaps about 1/4 inch. Draw a straight line up the paper. Cut the paper on straight line. Hold on to both pieces of cut paper. The piece of paper that will be wrapped around the canister can be decorated.
Step 3: Making Cone
Step 4: Make the Rocket
Step 5: 3...2...1
Break of a piece of the Alka-Seltzer and put it into the canister.
Find a flat location. Outside is best.
Fill your water dropper with water.
Step 6: Blast Off
Quickly set rocket down on flat surface with lid facing the ground.
Pop! Up goes your rocket!
Step 7: Suggestions
We do not suggest having kids use a film canister rocket without the extra paper. The rockets accelerate so fast that they could hurt someone.
Having trouble taping the cone on? Try making the cone so it will fit inside the paper cylinder.
Add an astronaut for fun with a film canister that the lid closes on the outside.
We do have film canisters for sale at catsscience.com but you can easily get them from e-bay.
Good luck and be safe.
Step 8: The Science
There is a lot of science behind the rocket going up. Newton's Three Laws of Motion come to mind for us. One being that an object at rest will stay at rest unless acted on by outside force and an object in motion will stay in motion unless acted upon by an outside force (simplified version). The rocket would just sit there if there was no force from the chemical change that is taking place inside the canister. The build up of pressure is released out the bottom of the rocket which causes the rocket to move. The rocket would continue to move up but gravity is a force that stops the rocket from continually going up.
Second law of motion essentially says that the more mass an object has, the more force will be needed to get that object to move or stop moving (simplified). Force = Mass x Acceleration (f=ma). If we put more mass on the rockets the more force will be needed to launch the rockets. So the less paper and tape we put on the rocket the higher it will fly (canisters with low mass on them can be dangerous. Be careful!).
Third law is action / reaction (at least that is the way I remember it). For every action there is a reaction. If you push a wall the wall pushes back. Try it with skates on and you will see what I mean. Think of a balloon that is filled with air. Let go of the balloon and the balloon moves in the opposite direction the air is coming out of - action / reaction. The rocket has gasses shooting out the bottom of the canister downward (action) and the canister moves upward (reaction).
We thought that kids could have fun adding weights (a jumbo paper clip is about 1 gram) to a rocket that had another canister on top. Put the weight in the top canister without the water and Alka-Seltzer and close the lid. We used a film canister that has an outside lid. This can help with understanding the second law of motion. The more mass that is in the container the more force will be needed to launch the rocket (the rocket will not go as high or as fast).
Please feel free to add more science concepts, correct any mistakes we made, and most of all have fun with us.