My daughter must have thought it was Christmas. Or Halloween. Or maybe that her father had lost it altogether — simply threw in the towel when it came to family nutrition.
Because there we were at the supermarket, loading our cart with bottle after bottle of Diet Coke and pack after pack of Mentos mints.
“Dad,” Emme began, “What are you … doing?”
Science, kid. That’s what we’re doing.
I love to do kitchen sink science experiments with my daughter, Emme, who is in second grade. We enjoy the tinkering, the learning, and the just plain fun of making cool stuff … happen. When you’re in the mood to combine science with good ol’ fashion crafts, this is the project for you.
You may have seen an Internet video floating around about adding Mentos mints to Diet Coke. It creates a geyser that easily stretches up to 10 feet — or even higher if you add more mints.
But what we like to do is build miniature paper roll rockets to add to the top of the bottle before the eruption. When the geyser hits, all that sweet, sugary foam launches your rocket — hopefully — into the atmosphere. Well, at least as high as the fence anyway ….
What You’ll Need
- Mentos mints (the regular mints, not the fruity kind)
- Diet Coke
- Rocket building materials. There’s no right way to do this. We like to use used toilet or paper towel rolls, some tape, string, construction paper, and crayons. Please, it doesn’t have to be perfect. And you don’t even need to build a rocket to enjoy the science of physical reactions at play.
What You Do
The end game is going to look like this: You open a bottle of Diet Coke, place a rocket on top, figure out a way to drop the Mentos mints in, and then stand back to watch the eruption and the launch of your creation. Boom. Easy Peasey.
But if you need a little guidance for rocket building, here’s what we do:
- Cut out some construction paper and roll it into a nose cone, applying it to the top of the paper roll “rocket” with tape. Cut out some more paper for side wings — which will act as stabilizers during lift off. We’ve found that bigger, heavier wings work best. But experiment away!
- This next step will allow you to launch the rocket at your leisure — instead of quickly adding mints, and then jamming the rocket back down before ignition. Cut two long slits in the side of your rocket. Turn rocket over so that the nose is facing the ground and then add as many mints as you’d like — the more the better. Then, add a slip of paper or card stock into the slit, so that when you turn the rocket back over, the mints won’t fall out of the bottom.
- Now, place your rocket on top of the open Diet Coke bottle. The mints will rest on the paper slip until you pull it out — at which point the mints will then fall into the soda.
- We like to tape string to the paper slip, so that we can back away before pulling the “launch cord.” And that’s it. There’s no right way to build a rocket, so mess around with designs to see how high you can launch one.
Here’s what my daughter’s cousin came up with on a lazy afternoon. Pretty cool, huh? Your rocket can look like anything! Including a garden gnome …
Please note: Our rockets have never really shot up that far. On the first attempt, it simply fell to the ground. But after several rockets and several attempts, we were able to launch one as high as the geyser. But that’s science in action. You have to try and try again. Plus, it’s just a plain fun challenge that will keep you entertained from construction to lift off.
Why It Works
The Mentos-Diet Coke experiment has been a thorn in the side of science for some time. Is it a chemical reaction that creates the geyser — like adding baking soda to vinegar? Or is it a physical reaction?
Turns out it is all about nucleation, which basically means giving the gas in the soda a place to form bubbles.
Next time you open a soda or bubbly water — anything in which carbon dioxide is added to the mix — go ahead and stick your finger in the liquid and see what happens. Bubbles form, right? That is nucleation in action.
It happens on a much, much broader scale when you drop in a mint. And here’s why Mentos are so special: Their surface is covered with millions of microscopic pores — the perfection place for gas bubbles to form. Drop in five or six or seven mints into a carbonated beverage, and suddenly you have millions upon millions of nucleation sites — or places for the bubbles to form. Those bubbles quickly add up and voila! An eruption of gas bubbles!
Messy science rocks.
Have fun messing around with different liquids or candies to create the biggest geyser. And have fun constructing your own rockets for maximum lift off. Just be ready with the garden hose to wash everything away.