Chemistry Experiments You Can Do At Home: The Alka Seltzer Rocket
So, maybe you’re a parent whose kids are curious about the way the world works. Or maybe you’re that kid. Maybe you are a teacher who would like to incorporate science activities into their classroom, but don’t know of experiments that are doable and safe. Maybe you are a Girl Scout or Boy Scout leader in the same situation. Well, I’m not going to say to look no further. You can always find new ideas or interesting variants on tried and true ideas. However, one experiment that I have found that 1st through 5th graders universally love is the Alka Seltzer Rocket.
You ask, is it safe? Well, there is inherent danger in anything we do, but this experiment only uses ingredients that can be found at the local supermarket or drugstore. There may be flying objects (film canister lids) in this experiment, but this can be avoided. Wearing safety glasses or goggles is always good practice, but not necessarily critical for safety in this experiment.
Materials needed:
Empty film canisters (must have the lids with them)
Alka Seltzer tablets (store brand works fine)
Water or other liquids you would like to test
Something to cut or crush the tablets with (if you like)
Stopwatch (not required; you can count seconds yourself, but it would be more accurate)
General Procedure:
You will want the film canister to be perfectly dry before adding anything to it; therefore, it helps to have several. Add a tablet (or part of one, I’ve found that a quarter of tablet works well, and allows you to experiment more for the same money) to the film canister. Then, add water and snap the lid on. Wait for the lid to pop off. I like to time this, because this way you can compare different conditions.
As an additional aspect, you could leave your finger gently on the lid. Once it pops (and it will), you can press it back on and see how many times you could repeat this cycle. It’s different for some conditions. (This will not work well if you don’t have your finger on it, as, unless constrained, it tends to pop to some distance.)
How it works:
Alka Seltzer contains both sodium bicarbonate (baking soda) and citric acid. Upon the addition of water (or some liquids), a chemical reaction occurs. It is rather similar to the classic volcano with baking soda and vinegar, and in general, accomplishes the same result: it produces carbon dioxide. However, this gas is being produced in a closed film container, and remains at a constant volume. Given a constant volume, a greater quantity of gas will produce higher pressures. In the rocket, eventually enough gas is produced to result in a pressure that will pop off the lid
But as fun as it is to see the lid pop off the film canister, it would be kind of boring if the only experiment you could do was add water. However, there are a whole host of variables you could test. What if you added more or less of the tablet? Crushed the tablet into a powder? Used hot or cold water? Going even further, what if you decided to compare rubbing alcohol to water? What if we added another acid, like vinegar or lemon juice to the tablet? Or even orange juice? Would it react faster, slower, or the same? What about a base, such as milk or soapy water? And while I wouldn’t recommend its use, Drano is basic as well, but much stronger. I’m sure you can come up with even more ideas that I may never be able to think of. Each one of these will also have further explanations than what I have listed above. Explaining what happens could be the topic for some interesting research for students. This is an ideal setup for practicing the scientific method.
You can also make a launchable rocket out of a film canister. First cut fins from corrugated cardboard. (Perfect way to use up old boxes) The fins need to be as tall as your film canister, but not taller, and not very wide. (The easiest way is to cut right triangles.) Also from the cardboard make a cone for the top of your rocket. Now, with silicone glue (such as GE Silicone II: you can find it in the hardware department), attach your fins equally spaced around the film canister. Also attach the cone on the bottom (away from the lid). To launch them, after adding the tablet and the liquid, put the lid on fast, place it upside down on a flat surface, and back away. Wait for a few seconds. I do have a few hints from experience. First, you will prefer to use the white colored film canisters that have a large portion of the lid inside the canister, rather than the black canister with gray lids. This will allows for more pressure to build up and a better launch. Secondly, make sure to make these in a very well ventilated place, and don’t do a lot at a time. Also make them at least 24 hours before you want to use them, preferably 48 hours. Lastly, use these either outdoors or in a place with a high ceiling. They will go high.
While this experiment is geared towards the elementary student, it can be expanded to the middle school and even high school student. Rather than simply doing hot and cold water, you could test water at various temperatures. Make sure to make a hypothesis beforehand! Older students could try to make a graph and try to see if there is a numerical relationship between the variables.
But no matter what you do: have fun!
One last tip: Don’t store the Alka Seltzer tablets for a year and then try to use them. They won’t work. You ask: how do I know? I’m guilty of trying it.
