• Gases and pressure
• Chemical reactions

• An empty, plastic 35mm film canister (which are getting more and more rare these days!) If you cannot locate one of these, you could try using any other small, lightweight, plastic container with a lid that easily pops on or off.
• An Alka-Seltzer^® or other antacid tablet
• Water

This experiment should be performed outdoors in an open area.

1. Add about one teaspoon of water to the film canister, and leave the lid open.
2. Break the antacid tablet in half and get ready to add it to the container.
3. This step requires you to be quick. Drop the broken antacid tablet into the container, then quickly close the lid and place the canister on the ground with the cap side down. Stand back a good distance, and wait for the rocket to launch. The Alka-Seltzer^® will react with the water in a reaction that produces carbon dioxide gas. The pressure of this gas will build and build until it exerts a force so great that it will blast the canister off of the cap, shooting the canister into the air.
4. After about 10 to 15 seconds, the canister will launch into the air!
5. Try repeating this experiment using different ratios of Alka-Seltzer^® to water, or using canisters of different types or sizes. You might also compare different brands of antacid tablets, or different methods for crushing the tablet before you add it to the canister. Compete with your friends to see who can make the rocket that shoots the highest!