Thursday, November 11, 2010

Film Canister Rocket

Looking for a fun science project to do with the kiddos?  Why not make a film canister rocket?

  • One empty 35mm plastic film canister and lid (You can ask a photo developing place to give you some, or you can order them HERE.
  • One fizzing antacid tablet (such as Alka-Seltzer)
  • Water
  • Safety goggles
1. Have your child put on the safety goggles and head outside.  If you want to try the indoor version, do not turn the canister upside down in step 5.
2. Break the antacid tablet in half.
3. Remove the lid from the film canister and put a teaspoon (5 ml) of water into the canister.
   Do the next 2 steps quickly

4. Drop the tablet half into the canister and snap the cap onto the canister (make sure that it snaps on tightly.)
5. Quickly put the canister on the ground CAP SIDE DOWN and STEP BACK at least 2 meters.
6. About 10 seconds later, you will hear a POP! and the film canister will launch into the air!
Caution: If it does not launch, wait at least 30 second before examining the canister. Usually the cap is not on tight enough.

When a seltzer tablet dissolves in water, a chemical change takes place and carbon dioxide gas (CO2) is formed. Most seltzer tablets contain a base called sodium bicarbonate (baking soda) and dehydrated citric acid. When the tablet is place in contact with the water, the citric acid combines with the baking soda. Acids and bases undergo a chemical reaction when they mix, producing a gas and salt. In the closed container, the newly created gas has no place to go since the closed container is already full of air. This is like trying to add more air to a balloon that is already full. The pressure inside the container eventually escapes by blowing up the balloon, blowing out the cork, or blowing off the lid. This is the same thing that happens when you open a can of soda. You notice the fizz that it makes. The carbon dioxide rushes out, making a woosh sound.

The project above is a DEMONSTRATION. To make it a true experiment, you can try to answer these questions:
1. Does water temperature affect how fast the rocket launches?
2. Does the size of the tablet piece affect how long it takes for the rocket to launch?
3. Can the flight path be controlled by adding fins or a nosecone to the canister?
4. How much water in the canister will give the highest flight?
5. How much water will give the quickest launch? 

If your not ready to try the experiment yourself, you can watch it on the video below:

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