Alka Seltzer Rockets
Introduction & Motivation
In The Alka Seltzer Reaction activity, we explored how surface area and temperature can affect the rate of the reaction between sodium bicarbonate and water. We saw that this reaction created a fizz, and from the chemical formula we know this gas that is being formed is carbon dioxide.
Just how much CO2 gas does this reaction generate? In this activity, students will take advantage of the gas being formed to create a rocket that will fly into the air! Students can choose to use the full film canister or just the cap to use as the reaction vessel (“reactor”).
Reaction: HCO3– (aq) + H+ (aq) → H2O (l) + CO2 (g)
Chemical Safety:
Materials
- Alka Seltzer tablets
- Water
- Teaspoon measures
- Educational Innovations Rocket Film Canisters or other small containers with snap-on lids
- Large tray and newspaper/paper towels to contain mess
- Decorating materials (colored paper, paper towel/toilet paper tubes, cardboard, tape, etc.)
Procedure
This activity can be messy and the rockets can sometimes shoot up to 20 feet in the air if launched straight up, so it is best performed in a big open space. This can be outside, or adapted to be inside if you have access to a large hallway.
If performed inside, use wedges of various angles on top of a desk to create a launch pad for the rockets and instruct students only to use the cap as their reaction vessel.
- Have the students design their rockets around the film canister. Prompt them to talk about what qualities of a rocket are important for flying high. Should it be light? Should it have a lot of fuel? Should it go fast?
- Fill the canisters with 1 teaspoon of water.
- Add a tablet to the canister and flip the canister upside down, and after 10 or so seconds, the canister will pop off from the lid. (Be sure to emphasize that the reaction evolves gas, builds up pressure, and this is what makes the rocket launch! The Alka Seltzer is not simply dissolving.)
- Debrief with students what they think went well with their rocket launch. Allow them to redesign the rocket and reaction and re-launch a few times before moving to the discussion.
Discussion
- How did you alter the reaction or design to make it take more/less time to blast off? Did this help the rocket fly higher?
- Did you want a delay before blast off? For what reason? What did this mean for temperature and surface area? (Delaying the reaction for long enough to move away from the launch pad is a smart design, this can be done by slowing the reaction.)
- Often times, chemical engineers have to work with other engineers to get a project done. Are there other types of engineers that could help here? (Mechanical and aerospace engineers are very helpful in this area!)
- Would NASA want to use our rockets for their space missions? (Probably not. These rockets are short-lived and do not go high enough or fast enough to escape Earth’s orbit. It is also relatively hard to control!)
- How do real rockets work? (Combustion, a chemical reaction between a fuel and oxygen to produce carbon dioxide and water!)