Film Cansiter Explosions Experiment
- Fill the film canister approximately 1/4 full with water.
- Add a Flat Fizzer to the canister, then place the cap on and flip the canister over. Do this as quickly and as snugly as you can. No need to rush but don’t take your time, either. Shake the canister once, put it down on a hard, flat surface, and lean back a little. (This is an important series of steps and you may need to burn a few tablet pieces getting the hang of it. Not to worry! We know you can do it.) Sometimes you can get two or more explosions out of one piece of tablet but you have to move quickly and smoothly to do it.
- Try setting off multiple reactions at the same time! See how many you are able to prepare before they start launching all over the place.
- Flat Fizzers
- Film Canister
- Adult supervision
How Does It Work?
When the tablet hits water, a chemical reaction takes place very quickly. Drop a piece into a glass of water and see for yourself. The bubbles are carbon dioxide gas (CO2) and there’s a lot of it! In the closed canister, the CO2 builds up so much pressure that the lid is forcibly removed from the inside. With an Alka-Seltzer tablet, the CO2 (the same gas that’s in a can of soda pop) is produced as a result of a chemical reaction with the water. With a can of soda, the CO2 is released as a result of opening the can or giving it a vigorous shaking. That’s a physical change and offers a good contrast between a physical and a chemical change.
Look at the ingredients of Alka-Seltzer. You will find that it contains citric acid and sodium bicarbonate (baking soda). When you drop the tablet in water, the acid and the baking soda react to rapidly produce CO2 gas. Gas pressure keeps building until finally the lid pops off. The lid of the canister is the outlet of least resistance for the gas pressure inside. Instead of the stronger sides or bottom bursting open, the lid pops off.
Take it Further!
- Fill the film canisters 1/4 full with water.
- Drop one of the spacers into each film canister. This spacer was designed specifically for these canisters in order to prevent the Flat Fizzers from touching the water. Make sure the water level is below the top of the spacer.
- Carefully place a Flat Fizzer on top of each of the spacers.
- Securely attach the caps to the film canisters. Be careful not to shake up the canister while you do this! At this point you have a film canister explosion that will only work once you turn them over. You can prepare as many as you want in this fashion without the worry of them launching too soon.
- Place the film canisters cap side up into the bottom piece of the 4” petri dish. Set the top piece of the dish on top of the canisters.
- When you are ready, grab both pieces of the petri dish and turn the whole setup over. Remove the bottom part of the dish (it should be on top now since you turned it over) and prepare yourself for a frenzy of flying film canisters!
Once you get the hang of the procedure, the goal is to determine the best combination (and there really is one) of water to tablet size to canister space to achieve higher and higher pops. Is it more water and less tablet? The other way around? Equal portions? Is right side up better or worse than upside down? Do you want to pop the cap or launch the canister? What happens if the water temperature is raised? So many questions…so much fun science to test and discover! It sounds like science fair data collection at its best.
Science Fair Connection
Launching a film canister is tons of fun, but it isn’t a science fair project. You can create a science fair project by identifying a variable, or something that changes, in this experiment. Let’s take a look at some of the variable options that might work:
- Once you’ve mastered the film canister technique above, it’s time to figure out how to make it go farther. For each trial, record the amount of water you use in the film canister (the variable changes), the weight of the tablet (use a kitchen scale for accuracy because this cannot change – it is your control), and the distance the canister traveled as a result. What amount of water mixed with a specific size of Alka-Seltzer tablet produces the longest distance?
- After you’ve determined the best amount of water to use with this size of tablet, try changing the temperature of the water. How does temperature affect the speed of the reaction and the distance traveled?
That’s just a couple of ideas, but you aren’t limited to those! Try coming up with different ideas of variables and give them a try. Remember, you can only change one thing at a time. If you are testing different amounts of water, make sure that the other factors are remaining the same!