Alka-Seltzer Rocket What happens when you have a build-up of gas? email to friend
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What happens when you have a build-up of gas? Don't answer that question! The gas in question is carbon dioxide and the explosion is nothing short of fun. Warning: It's impossible to do this activity just once. It is addicting and habit-forming. Proceed at your own risk!

Materials

Film canister with a snap-on lid. Look for a clear film canister, if possible.
Soda
Alka-Seltzer® tablet
Safety glasses
Paper towel for clean-up (you already know that this one is going to be good!)
Watch or timer
Notebook
Adult helper

IMPORTANT: This experiment requires you to wear protective safety glasses.

Experiment
Video

Pre-Flight Testing
1. Put on those safety glasses.
2. Fill the film canister 3/4 full with soda.
3. Quickly seal the canister with the lid and shake the thunder out of the can! Be careful to aim it away from your eyes. If you're lucky, the lid will pop off and fly into the air at warp speed.
4. What are you waiting for? Do it again! With every trial, change the volume of soda you use to produce the biggest POP! For this part of the experiment, try to keep the amount of shaking that you do with each trial the same for this part of the experiment (only change one variable at a time).
5. After you have determined the best volume of soda for the biggest bang, write down your findings in your notebook. Then start experimenting with how much you shake the film can. Remember to keep the volume of soda the same on each trial.

The Amazing Alka-Seltzer Rocket
1. Put on your safety glasses.
2. Divide the Alka-Seltzer tablet into four equal pieces.
3. Fill the film canister 1/2 of the way full with water.
4. Get ready to time the reaction of Alka-Seltzer and water. Place one of the pieces of Alka-Seltzer tablet in the film canister. What happens?
5. Time the reaction and write the time down. How long does the chemical reaction last? Why does it stop? Empty the liquid in the film canister into the waste bucket.
Alka-Seltzer Rocket

6. Repeat the experiment, but this time place the lid on the container. Remember to time the reaction. Write down your observations.
7. You should have two pieces of Alka-Seltzer tablet left. Repeat the experiment using one of the pieces of Alka-Seltzer, but this time you decide on the amount of water to put in the film canister. Do you think that it will make any difference?
8. Use the last piece of Alka-Seltzer to make up your own experiment. What do you want to find out? How are you going to do it? What are you going to measure?
9. Go ahead and experiment!

How does it work?

The first part of this experiment is just a variation of the classic Alka-Seltzer film canister rocket. The same principle is at work here. In both cases, carbon dioxide gas builds up so much pressure the lid is forcibly launched. With an Alka-Seltzer tablet, the CO2 is produced as a result of a chemical reaction. With the soda, the CO2 is produced as a result of vigorous shaking. This provides a good contrast between a physical and chemical change. You may need to experiment with several different film canisters before you are successful at building a rocket that launches with a blast. If the lid fits too tightly or too loosely, it won't work. To avoid a sticky mess, seltzer water can be used, which is simply carbonated, sugarless water.