We can make these rockets move with a tiny drop of soap! Water molecules stick to themselves with strong hydrogen bonds and the rocket sticks to the water in similar ways that take advantage of the surface tension. We can weaken the pull of the the water, the surface tension, with soap, a surfactant. If we place soap at the back of the rocket it has a weaker pull to the water than the front that does not have any soap. This means the force in the front is stronger than the force in the back and so the rocket shoots forward! Large rockets move under this same principle where one set of forces pushes more than the force of gravity keeping the rocket on the ground.
Activity Age: All ages
Activity Time: 5 minutes
Activity Clean-Up Time: 5 minutes
1 drop of dish soap (touching it with a toothpick with soap on the end works well too)
1 Container of water
1 triangle of foam 1 inch long with a slit cut halfway up
1. Fill your container with water
2. Place your triangle of foam in the container
3. Place one drop of soap at the top of the cut near the center of the triangle or touch a toothpick with soap to the same location
4. Watch your rocket blast off!
5. Try it again! You’ll have to rinse off your rocket and switch out your water to replicate your results.
Show us your different rocket designs! You can email your photos to firstname.lastname@example.org
Extra things to Try
-Change the shape of the foam
-Experiment with different water temperatures
-Adjust the length of the cut in the foam or make it wider
-Change the size of the foam rocket
-Color your rocket
-Change the type of soap you use
Did you like this activity? Let us know at email@example.com!