This project is a fun way to learn about chemical reactions. And a safe way to learn about rocketry. I am a high school Science teacher. In our grade 9 curriculum, we cover basic chemistry and space as topics. But this is a project that anyone interested in rockets, tinkering, or making can have fun doing.
Note about safety: This activity is a microchemistry project; using small quantities in a controlled setting allows for a safe demonstration of rocketry that is also engaging, and fun. Leaving a small amount of water in the pipet bulb acts as a propellant, and contains the reaction to the bulb. (You won't see any explosion, or flame so other clues of a chemical reaction will have to be used/discussed with the students.) Adding the weight of a 3D printed part minimizes the distance that the rocket will travel to ~15ft.
However, with any high school science lab activity (dealing with creative students) make sure that you have knowledge about lab safety, and use good classroom management. I have done this lab 100's of times with no "close calls". I would say the biggest safety precaution is making sure you dedicate an area of the room for your launch site, and that you carry the only piezoelectric device - so that you can be in control of when the launch occurs, and minimize the small chance of the rocket hitting any objects unintentionally (The rocket will only travel ~15 feet). Have students wear safety glasses or goggles as a precaution. (Also, always consult your local science safety regulations for required classroom lab safety equipment and lab safety procedures).
The micro rocket will be designed using a disposable micropipet with a 3D printed rocket overtop of it. A small amount of hydrogen gas will be generated using Mg and Vinegar. A small amount of oxygen gas will be generated using hydrogen peroxide and yeast. The gases will be collected in a plastic micropipet bulb using gas displacement. The gases will be combined to form water using the help of a piezoelectric sparker.
H2 + O2 → H2O (Note all the "2s" should be subscript)
1. Physical change vs Chemical change. Discuss clues to help decide if a chemical change has occurred: heat, light, or sound is given off, the change is difficult to reverse, a gas is produced, a new color is produced, a precipitate is produced. The number one indicator is that a new substance is made. (Three physical changes I discuss at the grade 9 level are change in state, change in form, and dissolving.)
2. The Particle Theory: Discuss the particle theory: all things are made of particles moving in random motion, adding heat to the substance makes the particles move faster, possibly breaking the attractive forces, and allowing a change of state. Taking heat away slows the particles down. I also discuss the unique properties of water here.
3. Atomic Theory: I introduce the atomic theory (including Bohr Rutherford Diagrams) and discuss elements vs compounds. I also introduce the idea of pure substances vs mixtures.
4. Chemical Equations: After doing Bohr Rutherford Diagrams I introduce ion formation. Then we look at ionic vs molecular compounds. I use the formation of water as an example of a molecular compound. We look at how to predict chemical formulas.
5. Balancing Equations: I teach the students the basics of balancing equations. (In our curriculum, more advanced balancing is done at the Gr 10 level.)
Questions for students to consider during the micro rocket activity:
1. Describe some physical properties of each reactant used e.g. vinegar is clear, colorless liquid
2. When Mg is added to vinegar is a chemical change or a physical change occurring? How do you know?
3. When Yeast is added to hydrogen peroxide is a chemical change, or physical change occurring? How do you know?
4. When the gases are collected in the bulb is it a pure substance, mixture, or compound? Explain
5. When the gases are collected, why is the water pushed out the bottom?
6. Based on the chemical formula of water, what ratios of gas will allow the rocket to fly the furthest?
7. When the piezoelectric is sparked, what is formed? Is this a pure substance, mixture, or compound (more than one description can be used).
8. After the piezoelectric is sparked, does a physical, or chemical change occur? What clues help you decide?
9. What angle of launch will allow the rocket to travel the furthest?
10. What are some physical properties of PLA filament that allow it to be useful for 3D printing?
Extension: Do different ratios of gas, do different angles of launch. Graph the results. 3D print rockets with different infill, tie in density. Research catalase, and tie in factors affecting enzyme function.
Step 1: 3D Design and Print the Rocket
Tinkercad was used to design a rocket that fits overtop of the bulb of a pipet. (You could design any payload you want.)
Step 2: Prepare the Rubber Stoppers
Prepare 3 rubber stoppers. The stoppers used were #2 one-holed rubber stoppers. You could use any other stopper, or cork as long as it will create a tight seal in the reaction plate well.
Cut a plastic pipet near the base of the bulb of the pipet. Cut it so that the pipet can be filled with water, but can still be turned upside down, and not lose the water. (You can use this as an opportunity to discuss the unique properties of water here with your students). There should also be enough space that it can easily fit on the end of the pipet used for the ignition apparatus.
Save the bulb for later. Slide the end of the pipet through the hole in the rubber stopper. I used a bit of glycerin (vegetable oil, or any other lubricant should work too) and a nail to help push the pipet through the stopper. (The video above shows how the stopper will be used during the gas generation step. For now, just pay attention to the assembly.)
Step 3: Prepare the Ignition Apparatus
The ignition apparatus was made by sliding two breadboard jumper cables up through the end of one of the pipet/rubber stopper assemblies.
Alligator clips were then clipped to the piezoelectric sparker. One jumper cable was connected to the ground on the side of the sparker, and the other jumper cable was connected to the end of the sparker.
Step 4: Fill the Bulb With Water
FIll the bulb with water from the tap. If you cut the bulb properly, you should be able to turn it upside down, and the water should stay in.
Step 5: Generating Gas
Gas was generated by putting the reactants in the reaction plate well, and then pushing the rubber stopper/pipet assembly over the well.
The pipet bulb filled with water is turned upside down, and placed over the top of the rubber stopper/pipet assembly that is covering the reaction plate well. The gas that is being produced pushes the water out. This is known as gas displacement. A plastic tray was put under the set up to catch any displaced water.
Oxygen is being generated on the left by adding yeast to hydrogen peroxide.
Hydrogen is being generated on the right by adding Mg metal to vinegar.
The amounts of each reactant do not need to be precise. But try to fill the reaction plate wells up as full as possible to minimize the amount of room air in the system. It is okay if some of the liquid moves up through the end of the pipet.
Step 6: Put the Rocket on the Bulb, Fill the Bulb With Gas
Put the rocket over the top of the bulb. Use the gas displacement method to put the desired amounts of hydrogen:oxygen into the bulb of the pipet.
Once the hydrogen and oxygen are being produced (from the previous step), you should wait for a second or two before displacing the water out of the pipet bulb to ensure that the amount of room air being pushed into the system is minimized.
Use the molecular formula of water to try and guess the best ratio of hydrogen to oxygen.
I used the rocket as a gauge, or fill line to estimate how much of each gas was in the bulb. For example, I pushed the bulb in 1/3rd, and stopped putting oxygen into the bulb when the water line reached the edge of the rocket. Then I displaced the rest with hydrogen to get a 1:2 ratio.
Leave a tiny amount of water in the bottom of the bulb as a propellant.
Step 7: Launch the Rocket
Once the desired amount of gas is put into the rocket, carefully put the rocket over top of the ignition apparatus. Make sure that there is still a small amount of water in the bottom to act as a propellant. Make sure the way is clear, do a count down, and spark the rocket. Measure the distance that the rocket travels.
Step 8: Extension: 3D Print Gas Collection Chambers, and Lauch Pad
There are so many skills that could be incorporated into this activity. You could 3D print a gas collection system, and launchpad; You could alter the angle of launch to see the effect on the distance obtained. Be creative.
Tinkercad Design (Note I printed this at 89% scale for a nice fit with a #2 stopper).
***You could also scale up this launchpad assembly/modify it to act as a test tube holder to dispense lab solutions.***
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