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Make Your Own Soda Geyser!

Submitted by on June 6, 2012 – 4:08 pmNo Comment

Soda Geyser - Sci Tech Discovery Center

Sci-Tech Discovery Center at home experiment: Soda Geyser


Carbonated drinks like most sodas are pumped with carbon dioxide to give the drinker the fizz feeling. This gas is suspended within the soda. Any shift in the forces inside can cause these gas molecules to come out of suspension. This effect can be seen when you shake a can. When shaken, the pressure increases as the gas inside tries to expand. When you open the container, this gas will push out to an area of lower pressure (a.k.a. the outside). As it leaves the container, the quick eruption will cause liquid to come out at the same time causing the subsequent spray!

When Mentos are dropped in, the surface tension of the soda is disrupted, allowing bubbles to form. Added to that, Mentos have thousands of microscopic pits that allow bubbles to form. As the bubbles expand, they are released and will push the soda out. In the video below, you can see the effect Mentos has on a bottle of diet coke — how cool is that soda geyser?

To create your own soda geyser, here’s what you need:


  • 2 Liter Soda Bottle (we’re using Diet Coke)
  • Roll of Mentos
  • Goggles (eye protection)
  • (Optional) 1 container for easy Mentos drop-off (we use a test tube)


1. Set up your geyser area. This science demonstration is VERY messy. You will want to make sure you have vertical height (outdoors). There is also a splash zone (soda can land several feet away from the bottle, especially in windy conditions).

Setup includes:

a. Set your soda bottle where you would like the geyser to happen.
b. Use a tarp if you would like to place under the bottle. This can help contain the spill. Another items you can use is a large plastic bin.
c. Leave the bottle closed until you are about to begin.

EXPERIMENT: Use other types of soda to see what reaction is best. You can also change the temperature of the soda to see if there is any effect.

2. Set up your drop-off container. In our case, we use a test tube. Setting up includes opening up the Mentos Roll and dropping the Mentos in our test tube.

EXPERIMENT: Use several different types of materials (salt, sugar, iron filings, etc.) and see what kind of reaction you get. Have them ready so that you can do the experiment trials right after each other.

3. Use eye protection for the next part. Open your soda bottle and drop your Mentos inside as quickly as possible. Make sure not to stare directly into the hole of the bottle as the soda can hurt your eyes. The resulting geyser will happen quickly. To avoid getting too wet, you will need to step back faster in order to avoid the spray. Make sure to have a clear back up area. Some Mentos may come out from the rapid release. If you are using other materials (such as salt, iron filings, etc.), these substances can get into your eyes and scratch your cornea. Avoid inhalation of the geyser as well as digestion.

Remember to have an adult around and have fun!

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