Erupting Volcano

Make An Erupting Volcano Project


Basic Earth Science Projects For Kids

Mt St HelensAn erupting volcano project was the goal, so now that we decided how to make a volcano there are several ways to make it erupt. Here are the links to building the model volcano if you missed that step:

Paper mache volcano
Home-made play dough model volcano
Moist soil method
Construction paper (not recommended for multiple volcano eruptions)
Using sand
Using plaster
Using joint compound
Spray foam method (for home volcano projects)

Active links have been completed on this site already. As you can see, there are several methods we did not do (at least not yet).  We left those as ideas for imaginative students to work on for now. Just check the table of contents or the directory of projects page for updates, as well as the earth science page for related projects.


Baking Soda Methods

A single search on the internet will show several erupting volcano recipes using baking soda and vinegar, some with detailed explanations, others with absolutely nothing except mix and watch. There are two general types in this category. Adding soda to liquid or adding liquid to soda. Let me explain …


Vinegar in the bottle first

For erupting volcano projects using this technique, a liquid mixture is put in the bottle first. Baking soda is added through a funnel, or wrapped in tissue paper and forced in the bottle opening. Hot water is used in some, not in others, and most all use a coloring material of some type to make our simulated lava look more realistic. Here are some of the recipes we tried.

Trial 1

1/4 cup vinegar (up to a cup if you have a large bottle)
2 tablespoons baking soda
cherry jello granules

Place the vinegar in the bottle. This can be done before the bottle is put inside the model volcano in case you want to prepare ahead of time, otherwise, a small funnel works just fine. Stir the baking soda and enough cherry jello mix to make a pinkish powder. Either wrap the soda mixture in tissue paper or use a funnel to add it directly into the bottle. Tissue helps get all the soda in the vinegar at once, but if the funnel hole is large enough, that method works just fine. Either way, the goal is to get the baking soda into the vinegar as fast as you can. Stand back and watch what happens – Erupting Volcano!

Trial 2

warm water
1/4 cup vinegar (up to a cup for large bottles)
2 tablespoons baking soda
cherry jello granules

Fill the bottle about 2/3 full with very warm water. Add vinegar to the bottle. Mix the baking soda and enough jello together to make the mixture a light pink. When ready for the erupting volcano and add the powder to the vinegar all at once using either the funnel or tissue paper method noted above. The reaction can be quite fast, so add the soda mix quickly and stand back so everyone can see.

Trial 3

warm water
1/4 cup vinegar (up to a cup for larger bottles)
6 – 8 drops liquid dish soap
>2 tablespoons baking soda
cherry jello granules

Fill the bottle about 2/3 full with very warm water. Add the vinegar and dish soap to the bottle. Mix the baking soda and jello together until the mixture is pinkish in color. To initiate the erupting volcano project, add the soda mixture to the vinegar all at once using the funnel or tissue paper method. Stand back so everyone can see the erupting volcano.


What’s the difference?

Notice that only one item was changed in each of the above trials. Students should understand that controlling the variables in a lab project or science experiment is important to determine what caused any observed changes in the results.

The straight vinegar method in Trial 1 worked just fine for our erupting volcano project. You can use red or orange jello, food coloring, or even koolaid crystals if desired. We stuck with gelatin crystals because it was easy to use and gave the simulated lava a chunkier texture than food coloring or koolaid.

Trial 2 had a more violent reaction, meaning it was a bit more spectacular. It was harder to get all the baking soda in the bottle with a funnel before the reaction started producing our lava, but if you’re looking for fast reactions, this would be one to consider. In this case the warm water acted as a catalyst, where the temperature of the water helped speed up the reaction. The cherry jello has no noticeable effect on the eruption other than color, and a slight change in the texture of the lava.

For Trial 3, websites differ on what the soap does for the eruption. Yes it changes surface tension, and yes it can make bubbles of its own, but we found no significant change in the frothiness of the lava bubbles or the amount that was produced. It did slow the reaction down a bit and there may have been a bit more lava than with trial 1, but we also didn’t have to wait for the bottle to fill with ‘lava’ before it started spilling out onto our model volcano as in trial 1. This method is worth doing, but the simpler the better, so for me trial 1 wins over this one.



Baking Soda in the bottle first

For ease in doing the experiment, adding the vinegar last wins hands down. All of the trials are worth doing, but if you would like to stop the research and do the erupting volcano experiment now, go for it with the next trial shown below. You’ll be happy with the result.

Trial 4

1/4 cup vinegar (up to a cup if you have a large bottle)
2 tablespoons baking soda
cherry jello granules

Mix the baking soda and jello crystals until pinkish in color and use a funnel to get the mixture in the bottle. That’s it. When you’re ready for the erupting volcano, use a funnel to pour all the vinegar into the bottle at once, then take the funnel out quickly. The key is to get all the vinegar into to bottle as fast as possible and move out of the way. It won’t explode, but lava bubbles do ooze out pretty fast once the reaction starts.


Trial 5

warm water
1/4 cup vinegar (up to a cup for large bottles)
2 tablespoons baking soda
cherry jello granules

Fill the bottle about 2/3 full with very warm water. Pour in the baking soda and jello for desired color and mix. It is easier to cap the bottle and shake it outside the volcano, but using a funnel and a straw to mix everything together with the bottle inside the volcano works ok as well. When ready for the erupting volcano, add the vinegar to the bottle with the funnel. Stand back quickly so all can see.


Trial 6

warm water
1/4 cup vinegar (up to a cup for larger bottles)
6 – 8 drops liquid dish soap
cherry jello granules

Mix enough jello with the baking soda until you have a slight pink color and add it to the bottle already filled about 2/3rd’s full with very warm water. Mix well by shaking the bottle or stirring with a straw. Add the soap and stir gently with a straw so as not to make too many bubbles. When ready for the erupting volcano, add the vinegar quickly through a funnel and move back for others to see.


What’s the difference?

We found Trials 4, 5 and 6 were much easier to control than trying to add the baking soda mixture last. It is also important to note, the more baking soda and vinegar you use, the more lava will be created. Some sites say to use a 2 liter bottle, but I don’t think it is necessary. We used a small 12 oz. water bottle and had great results. Unless you just want a gigantic erupting volcano, that size is more than large enough to demonstrate the basic earth science concepts.

If you have a large class, it would be worthwhile assigning a different erupting volcano method to each group to spark a discussion on which worked best at the end of the lab.


Diet Coke and Mentos

Ok, although a bit over-worked, no self-respecting erupting volcano website would be complete without a section on diet coke and mentos. We did things a bit different than other folks, just to see if smaller worked ok as well. We found it did just fine.

Trial 7

12 oz. bottle of regular diet coke
3 mint mentos

Rather than building a model volcano around a 2 liter bottle of diet coke and shooting off a geyser that somebody would have to clean up (it is fun, and rather spectacular if you want to give it a try), we decided to use our small water bottle model to see if it would work there as well. Smaller was ok, but we had to use a freshly opened 12 oz. bottle of regular diet coke to make it work. In other words, if we poured the diet coke into our original water bottle, no matter how careful we were, too much of the fizz was released in the pouring process and the desired erupting volcano reaction with mentos was disappointing at best. However, our model volcano also accepted a 12 oz. soda bottle just fine, so all went well after that minor change. There were no expectations of getting a 10 foot stack of brown lava shooting up the air, but we did get a good stream.

Remove the original bottle and replace it with a freshly opened 12 oz. bottle of regular diet coke. Flavored diet cokes don’t react as well, and neither do flavored mentos. Original for both is best. With the open bottle in the model, you are ready to go.

Now the goal is to get all the mentos in the bottle as fast as you can. One way that works quite well is to drill a small hole in the center of each mint and hang all 3 by a string. When ready for the erupting volcano, hold the string with all 3 mentos centered over the bottle hole and let go. Swoosh. The resulting volcanic eruption occurs fast.

Drilling holes in candy isn’t as easy as it looks, so another method is to use a plastic tube, or roll a small square piece of paper around the mentos so that you have a small paper cylinder filled with three of the mints. Place another piece of paper under one end of the cylinder so the candy doesn’t fall out until you are ready. Rest the bottom paper on the open bottle with the mentos centered over the hole. When you are ready for the erupting volcano, pull the flat piece of paper out from under the cylinder and let all three mentos fall into the bottle. It may take a little practice getting all the mentos in the bottle at the same time, but it is a fun way to do the project.



No time to get Mentos? Try this instead …

Trial 8

12 oz. bottle of any diet soda
2 tablespoons salt

Any carbonated drink will work, but those with sugar in them slow the reaction down, not to mention that sugar is sticky and makes the cleanup harder. If you want to be bold, go ahead with the 2 liter variety, but we recommend that for outside demonstrations only. It probably won’t shoot up as high as the mentos, but the foam continues until the bottle is almost empty.

Open a new 12 oz. bottle of diet soda, flavors may slow the reaction a bit as well, but we did just fine with a diet cherry cola. Place the open bottle under the model volcano and you’re all set.

Put your finger over the end of the funnel and pour about 2 tablespoons of regular table salt into the funnel. When ready for brown lava, hold the funnel over the soda, move your finger off the end and get all the salt in as fast as you can. Then move out of the way. This gets messy as at least 10 of the 12 ounces we tried ended up in the bottom of the model volcano.


What’s happening?


With the baking soda and vinegar, a chemical reaction occurs that quickly releases a gas called carbon dioxide, or CO2. It is the same gas that makes the fizz in a carbonated soda like diet coke, but the way it gets released into a gas is different.

To see how it works, we need to look at the components. Baking soda is also known as sodium bicarbonate, (grandma might have called it bicarbonate of soda) and it’s a powder that reacts as a slight base. It has a chemical formula NaHCO3. Vinegar is an acid, actually acetic acid in water. It has a chemical formula of C2H4O2, or is sometimes written as CH3COOH to closer represent how it bonds as a molecule.

Without getting to deep in the chemistry, when the two are mixed, a hydrogen atom effectively changes places with a sodium atom and we end up with two new substances – carbonic acid and sodium acetate. The carbonic acid then quickly breaks down further into water and carbon dioxide. It is the carbon dioxide escaping from solution that causes the frothy foam we are using as the lava for our erupting volcano.

In case you are interested in chemical formulas, ignoring some of the ions, the primary process looks something like this
NaHCO3 + C2H4O2 –> NaC2H3O2 + H2CO3 –> NaC2H3O2 + H2O +CO2
soda      + vinegar   –> sodium acetate + carbonic acid –> carbon dioxide (and some other stuff)


For diet coke and mentos, the jury is still out on exactly why the violent reaction occurs. Some say it is strictly mechanical, where the surface of the mentos provides many cracks and jagged edges as nucleation sites for CO2 to form larger bubbles and escape. Others claim that the dissolving mint candy interferes with the the normal surface tension in the water, which is largely responsible for holding the CO2 in suspension. Some claim both happen. A quick search on the internet with the seed question “why does diet coke and mentos explode” will provide all the research needed for the various theories.

For our purposes, it is sufficient to say that it makes sense for both the above to occur. The suspended CO2 in the soda wants to come out of solution all by itself already, and is why if you leave a carbonated soft drink open, it will be flat in just a few hours. The CO2 stays in solution partly because of the pressure in the bottle, and partly because water molecules tend to stick together. Because of that surface tension, they tend to surround the CO2 and hold it in suspension. When the mentos are dropped into the diet soda, just like salt in a carbonated drink, or ice cream in a glass of cola, the CO2 immediately starts forming bubbles and rises to the surface. It makes sense that the dissolving candy also affects surface tension such that it is easier for the CO2 to escape. Add lots of spots on the surface of the mentos where bubbles can start forming and things happen quickly from there. Since the mentos also sink, and the reaction is quite fast, the escaping gas rapidly moves to the surface, passes it, and takes a bunch (underscore a bunch) of the soda with it right out of the bottle.

To show that the mechanical effect works all by itself, Trial 8 uses only soda and table salt. The salt dissolves in the water, but there is no chemical reaction to speak of going on. It is an example of a mechanical release of the gas through nucleation, or bubble formation on the edges of the salt crystal themselves. Since the reaction is not as violent, we’re thinking the surface tension part of the explanation has merit.

If you would like to comment, discuss other methods you’ve tried for making erupting volcanoes, or provide other fun projects with any of the lava producing materials discussed here, please do so. We would love to hear from you.


And for fascinating information on Real Eruptions, we highly recommend: Eruptions that Shook the World.  It is a Spellbinding exploration of the history’s greatest volcanic events and their impacts on the history of humankind.


Eruptions that Shook the World







18 thoughts on “Make An Erupting Volcano Project

    1. Hi Chip! – take a look at the what’s happening section for how this simulated lava works

  1. Thanks for the question Rinae … as written, the volcano project is more on the middle school grade level, but if you were to give the students several options on how to construct the volcano as noted in that project, and dig a bit deeper into the actual geology behind the types of volcanoes, it certainly could be used in a grade 9 class setting.

  2. It didn’t work so I tried just the bottle and vinegar and baking soda!

  3. Thanks Anthony. Not sure what happened with the others but glad vinegar and baking soda is a sure way to get the reaction!

  4. i am a sixth grade student and having trouble understanding the explanation on the chemical reactions so i can paraphrase for my project

  5. Hi Bonquita

    hmmm … let me try.

    When vinegar is added to baking soda a chemical reaction happens. That chemical reaction releases gas bubbles very quickly. As the gas bubbles expand and rise to the surface, they bring some of the liquid with it so the whole mixture looks like a rapidly rising foam. That foam is the simulated or “pretend” lava in our erupting volcano experiment.

    Is that better?

  6. Wow, great summary of the volcano methods out there! Thanks for providing this info, and the framework for comparing methods as experiments. My 2nd grader and I will be leading a volcano workshop with a 4th grader, and this should be fun to set-up. Really appreciate your explanations!

  7. This blog about Make An Erupting Volcano Project.
    has helped me, congrats, is a very good topic!

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