Earth Science Projects Archive

  • cricket Chirp Thermometer

    In this experiment, you’re going to use the chirping of crickets to tell you the temperature. This experiment can be performed for fun or it can be performed and documented to be used in your science fair project that studies the animals in a particular environment. It takes a bit of time and some mathematical effort, so you may want a parent to help you out! This experiment takes about ten minutes, so it’s a fairly fast process once you have everything that you need.

    Note: Make sure your outdoor temperature is between 55 and 100 degrees Fahrenheit.

    What You Will Need:

    1 cricket container (A Kritter Keeper can be purchased at your local pet store)

    A bunch of crickets (You can either catch wild ones or purchase them at a pet store. Note: Make sure that they are full-grown adult crickets.) If you are in an area that has an abundance of crickets, you can try using their chirps to do the experiment.

    1 Outdoor thermometer (To check your answers.)

    1 Stopwatch

    1 piece of paper

    1 pen or pencil

    1 calculator (optional)



    Step 1: Place your crickets outside after dark.

    Step 2: After waiting for your crickets to begin chirping, use your stopwatch to count the number of chirps that you hear in the span of 14 seconds.

    Step 3: Write that number down and then add 40 to the number of chirps that you counted. You’re resulting number, after your addition, should be the temperature.

    (For example, if you count 20 chirps in the span of 14 seconds and then you add the number 40 to the number of chirps, you should get 60. So you should end up having the temperature of 60 degrees Fahrenheit.)


    Note: To get the temperature for Celsius, you will need to count the number of chirps in the span of 25 seconds. Use that resulting number and divide it by 3, then add 4. You’re resulting temperature should be in Celsius.

    (For example, if the crickets chirp 48 times and you divide that number by 3 and then add 4, your resulting answer will be 20 degrees Celsius.)

  • Fog Formation

    For this project, you’ll be conducting an experiment. What makes fog? The project, itself, is a simple one and will only take about 2 to 3 hours to complete. This is a very good topic for science fairs if you’re willing to do a bit more research than “hands on” experimentation.

    Necessary Items:



    *2 empty pop bottles

    *Hot water

    *Cold water

    *2 ice cubes that can be lodged in the neck of the pop bottles.


    Step 1: Empty and rinse out your soda bottles.

    Step 2: Label one soda bottle with the word “Cold” and one with the word, “Hot”.

    Step 3: Take your bottle that says, “Cold” and fill it about a quarter of the way up with cold water. Once you have the water in your bottle, wedge the ice cube into the neck of the bottle (Do not let the ice cube fall into the bottle. It must remain lodged in the neck) and watch to see what happens. Use your journal to record your findings.

    Step 4: Take your bottle that says, “Hot” and fill it a quarter of the way up with hot water. (The water does not need to be boiling. Simple hot water from your tap will suffice.) Now place an ice cube into the neck of the bottle labeled “Hot”. Watch closely and record your findings.

    Note: Fog will be produced in one of the two bottles. This simulation represents the production of radiation fog. As your project, you can document and record your findings and explain why this happens.

  • The Double Colored Flower

    Have you ever gone out and picked a white flower so that you could put it in colored water to dye the petals? Carnations are a particularly great flower to use with dye experiments. In this experiment, you’re going to be getting a little more creative. You’re going to be conducting an experiment that focuses on the inner workings of the flowers stem.

    This experiment will take 10 minutes to prep and the observation time will be between 5 to 10 hours.

    What you will need:

    At least one white carnation

    2 pint or quart jars

    Food coloring (Red – water soluble – dye)

    Scissors or a blade (to split the flower stem down the middle)



    Step 1: Fill both jars with water. Add the red dye to only one of the jars of water.

    Step 2: Split the stem of the white flower down the middle.

    Step 3: Place 1/2 of the stem in the clear water and the other half into the red dye.

    In Summary:

    Keep an eye on what happens to the flower petals and document or discuss what happens to them over the next 5 to 10 hours.

    The water is pulled up through the capillaries in the stem and up into the petals of the flower. Will the entire flower change color or will only half of the flower change color? If your flower has leaves on the stem, pay attention to those too. Not just the petals will change color. You can use this experiment to explain the inner workings of plant structure in a science fair experiment.

  • Dehydrated Potato Experiment

    Dehydrated Potato Example


    Dehydration is a condition that almost any person can relate to. When we get too hot and don’t take in enough fluids, it’s possible to suffer from anything ranging from a headache, to disorientation, and in the most extreme cases, even death! Did you know that dehydration is something that affects a huge number of organisms, even plants? With this simple experiment we will look at the effects of dehydration on an uncooked potato.


    Here’s What You Will Need

    • One potato. It’s best to use smaller potatoes as this will reduce the time it takes to complete the experiment. The experiment generally takes up to one hour.
    • Two dishes or small plastic containers.
    • A knife and a kitchen cutting board.
    • Any type of salt used for cooking.
    • Fresh water.
    • Paper and a pencil or permanent marker.


    Carrying Out the Experiment

    Write ‘Salt Water’ on a piece of paper, and place this under one of the dishes or containers.

    Pour the same amount of fresh water into each dish or container. You will be placing the potato in the water, but it does not need to be submerged. Less than about 1/2 an inch of water is enough for this experiment.

    In the ‘Salt Water’ dish, add two tablespoons of salt. If you don’t have a measuring device, just add two heaping dinner spoons of salt to the water and stir to dissolve.

    Now cut the potato in half as close to the middle as you can.  Lengthwise or the other way is just fine, then place one half into each dish or container, with the sliced side facing down.

    Now it’s time to wait. Leave the potato slices for up to one hour, after which you will be able to note the effects of dehydration.


    Results of the Experiment

    What do you think will happen to the potato slices? After one hour, there will be a clear difference between each potato. The potato bathing in regular water should be mostly unchanged. However, the potato in the salt water will be shriveled and dehydrated. Salt works by pulling moisture out of the potato. If you were to use different additives in the water, you would observe different results. Try experimenting with other non toxic household ingredients and note the different effects.

    This is also a good example of what happens in the Osmosis process, if you want to understand why it works in this experiment.

    Here is a graphic that will help explain that as well ..

    Difference Between Osmosis and Reverse Osmosis. Water passing through a semi-permeable membrane



    Here are some examples of dehydration kits. They don’t use the same concept as we did above, but the result after removing the water is the same …


  • Make A Volcano Project

    Build Your Own Volcano



    Basic Earth Science Projects For Kids

    How to make a volcano? Hurl cosmic material into space, have it collect into a planet sized object (like earth for example), put it in orbit around a sun, give it a few million years for the surface to cool to a hard crust, and poof – you have the basic ingredients needed. If hot molten magma under great pressure then manages to escape through weak spots in that crust, we have a volcano.

    It’s a truly fascinating subject, and this project attempts to frame the question of how to make a volcano within that larger context of basic earth science. The topic area is rich enough to support projects at all grade levels, but this experiment is listed as a 3rd grade science project since I believe it is the first age group that can perform the steps needed with very little supervision.

    Under the right circumstances, it could also be used as a 4th grade science project, or possibly even as late as 5th grade. However, I actually performed this volcano project with two youngsters, one in pre-school and the other a kindergarten student. Granted, I was always there, and they won’t get the larger part of the earth science equation yet, but they (and I) had a great time from start to finish.

    Since our goal is to help young students tie this exercise to the larger earth science topic, additional earth science projects will be added in solar power, earthquake, tsunami, hydro energy, wind power and other related areas as time allows.

    But first – let’s answer the question on how to make a volcano using things we probably have around the house. It’s a fun science project that can be done several ways. Here is the first: papier-mâché (forever to be known here as paper-mache).



    The “how to make a volcano” science project is designed to help young students learn more about earth science by looking specifically at volcanoes. We’ll also learn how common household items can be used to build useful models, with an element of creativity required to make the model realistic. Hopefully we’ll discover a few new science terms along the way as well. The experiment is done in two steps. First, we figure out how to make a volcano, then we look at fun ways to make it erupt.


    Materials needed Make a Volcano with Paper-Mache

    – 1 newspaper
    – 1-2 cups flour, depending on the volcano size desired
    – 1-2 cups water
    – 1 medium size bowl
    – 1 fork or spoon to stir with
    – 1 pair of scissors
    – 1 roll scotch or masking tape
    – 1 small plastic bag
    – 1 pencil or marker
    – 1 plastic or glass bottle
    – 1 medium size box
    – Paint
    – 1 medium size paint brush, (a couple more if you have several helpers)
    – Rocks, sticks, tips of pine trees or shrubs and anything else you would like to use to decorate the volcano with to make it more realistic.

    Some notes on the above materials. First, just about any drink bottle will work, but keep in mind that bottle size will determine volcano height. That’s why the amount of flour and water is shown as variable. Second, having sides around the volcano helps keep the “lava” in part 2 of the project contained. However, if having sides is not desired, then substitute a flat piece of cardboard, or even some thin plywood for the box as a stable base for the model volcano. Finally, any paint will do, but a water based acrylic is recommended for easy clean up. They also dry quickly with little need to vent paint fumes. Green, blue, yellow, red, white and black or brown should provide plenty of variety. We cut the bottom out of a small Styrofoam glass to use for mixing colors and dispensing the paint.



    Other than gathering the materials, no advance preparation to make a volcano is needed.


    Project Day

    If done as a demonstration for 2nd, 1st grade or even kindergarten science projects, then a single set of materials is all that’s needed. Gather the students around, let them take turns helping as time allows and follow the directions shown below. It will take at least one class period for them to make a volcano with paper-mache, another to paint and a third to add final decorations and make it erupt. At least one full day will be needed between these steps to allow for drying time.

    If done as an in-class 3rd grade science project, split the class into smaller groups as materials allow. It will still take the same amount of time to complete the project, but in this scenario, each group of students gets to make a volcano of their own. Then they can decorate it and decide what to use as simulated lava to make it erupt.

    As a final comment, a “facts about volcanoes” page will be added soon as a ready reference for information on how things work in real volcanoes. While the paper-mache volcano project was designed to be a fun science project for kids, the volcano information sheet will help tie it all together to the earth science topic.


    Project Steps

    Step1 – Get a medium size box and mark where you want to cut the sides.



    Step 2 – Cut the box, but do not discard the sides.  Place the bottle in the box and draw a circle around its base big enough for the bottle to slip through.



    Step 3 – Cut the box sides into about 1 inch strips. Yup, those are my lab rats!



    Step 4 – Cut the hole and make sure the box fits over the bottle.



    Step 5 – Cover the bottle with a small plastic bag to keep building materials from sticking to the side of the bottle.

    Make a volcano structure around the bottle with 1 inch cardboard strips that were left over from the cutoff sides of the box. Staples can be used to hold the strips together if desired, but be sure to put plenty of tape around the crater of the volcano, and make sure not to cover the top of the bottle up.

    If you prefer a stronger structure, chicken wire does great … but you’ll need to supervise that, (and it really isn’t needed).



    Step 6 – Mix about a cup of flour with enough water to make homemade paste. It should be about the consistency of elmers glue.

    Cut or tear several dozen 1 inch strips of newspaper, but leave at least a sheet or two to put under the box to make the cleanup part easy.

    Holding one end of a newspaper strip, drag it through the paste and gently squeegee off any excess glue with fingers on your other hand. The goal is for the paper to be wet, but not dripping with glue.

    Add each glue-soaked strip of newspaper to the volcano support structure, gently smoothing each down as you go. If the forming mountainsides get too much glue on them (you’ll know), just add some dry strips to soak it up.



    Step 7 – Continue until there are several layers of newspaper strips over the entire mountain, and on the bottom of the box.

    If you picked a larger bottle, you may need to mix more paste and cut more paper strips to get to this point, but when done, it is time to clean up for the day and let the model volcano dry.



    Step 8 – Add some paint for effect.  Green makes a great start for grass, trees, etc – and if the volcano is tall, only rocks can be seen near the top. We used brown for that. Sky is blue … etc. Paint the volcano to make it as realistic as you can.

    You can go to the next step if desired, but it would be best to let the paint dry first if you can afford the time.



    Step 9 – Now decorate the volcano to make it look even more realistic. Add rocks, sticks for fallen tree-trunks, bushes, maybe even houses from a monopoly set, etc. (Then discuss why it might not be a good idea to live near a volcano).



    That takes care of how to build a volcano using paper-mache. It’s a bit messy, but easy enough to do.  I don’t think we’ll need to explore these here, but several other construction methods you might want to ask the students to do might include …

    Moist soil
    Homemade play-dough
    And possibly a couple others they come up with on their own.  Let the imagination run wild … as they say.  Let them be creative!

    In the meantime, part 2 of any volcano-making project just has to be about making it erupt.  And that’s next!




    Making The Eruption

    There are many recipes for volcanic eruptions using baking soda and vinegar, and different reasons to use each of the ingredients. There are a couple other chemical recipes I’m not going to add for safety reasons, but diet coke and mentos is sure fun. It is rather dramatic, very messy, and therefore quite popular! Bring plenty of paper towels, but the kids love it. Did I say messy?

    Anyway, you decide which simulated volcanic eruption you would like to try. They are all fun, and if you are doing it as an in-class project, perhaps assigning a different one to each group to see which is more realistic would be fun. Here are the links for part 2 for how to make a volcano erupt. Enjoy!

    Baking Soda and Vinegar methods
    Diet Coke and Mentos


    What just happened?

    For the teacher

    Hopefully, everybody had a great time. But also hidden in the project was some learning on how to make a volcano out of common household items. This may not sound like a major event, but modeling what we see in nature so that we may attempt to better understand it under conditions we can control is part of the scientific process at its most fundamental level. Making a small-scale model volcano, and figuring out to simulate volcano eruptions may be a fun way to do science … but science it is.

    Do be sure to discuss some of the items on the volcano information sheet (coming soon), or better yet, provide a copy to the students to review during the project. If there are more than 2 or 3 to a group, this is a great way to focus on learning more about volcanoes during times when they cannot directly participate. When introducing the project, ask them if they can figure out where magma comes from, how it gets to the surface and what happens when it does. That should bring up a number of new earth science terms for discussion as well.

    We’ll cover what causes the simulated volcanic eruptions in part 2’s project discussions.

    For the students

    At this grade level, we won’t assume T-shirts will go by the way of lab coats, and each of them striving to become the next Nobel prize winning scientists. Having fun while learning some basic skills in scientific discovery is plenty at this point. Reading the volcano information sheet (or doing a report on their own) should provide more than enough information on volcanoes, as well as a fun introduction to basic earth science.

    Once the model volcano is built (and the paper-mache mess is cleaned up), summarize this part of the earth science project with a few facts about volcanoes. Answering the above questions about magma as a group is also a great lead in for part 2 – making the volcano erupt.

    For the Teacher (with less mess)

    You can find several volcano kits on Amazon that are pretty much out of the box ready to go. Enjoy!!



    As an additional resource and fascinating reading on real eruptions, we 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




  • How Light Affects Seed Germination

    When a seed that has been planted starts to sprout, it is called germination. Different seeds require different conditions to germinate, but they all need three things: light, heat, and water. In this experiment we’ll investigate how light affects the germination of bean seeds.


    3 clear CD cases, with the plastic piece that holds the CD removed
    Potting soil or seed starter
    Small pail
    Clear tape
    1 package of bean seeds (pinto or lima beans work well)
    A piece of thin, see through cloth such as cheese cloth
    A piece of dark colored cloth or a small cardboard box
    An eyedropper or small squeeze bottle like eye drops come in (wash it thoroughly first)


    Place a few handfuls of soil or seed starter into the pail.
    Add enough water to make sure that the soil is moist.
    Open the CD cases with the hinge to the side so that the small openings in the case are on the top and bottom. Add a small amount of soil to each case. Make sure to fill the cases only half way so that your seed has room to grow.
    Place your seed in the middle of the soil with the small dot facing downward. The bean should be positioned so that it is in the shape of a frown rather than a smile. You may want to plant two seeds to make sure at least one germinates.
    Add a few more drops of water onto the seed.
    Close the CD case and use the clear tape to secure the bottom and sides. Make sure to leave the top openings uncovered so you can water your seeds.
    Place the cases in a warm area of the house and leave one case uncovered.
    Cover the second case with cheese cloth or other material that will let some light through.
    Cover the third case with the dark material or place it in the cardboard box. (make sure all the cases are standing upright with the bottom of the seed facing downward)
    Use the eyedropper or squeeze bottle to water your seeds each day, giving each seed the same amount.
    Check the seeds each day to see if they have germinated and record the results in a notebook.

    You should see that the seed in the uncovered case will germinate first, followed by the one with the see through cloth. The seed that doesn’t get any light should take the longest to germinate.

    If you want to continue your experiment to see how light affects plant growth, leave the seeds where they are and continue watering them. As they grow, you’ll notice a big difference in the growth rate of the three plants as well as in their color.

  • Earth Science – Seed Germination

    Post Image
    Adult help required with cutting tool.

    Do seeds germinate better in paper or on soil? Which one provides a better start and which one ends up with larger and hardier plants? Find out by doing our simple seed germination science experiment. Bear in mind that if you want to showcase these seeds and plants in a science project you’ll need to plant them well in advance of a science fair, if that’s what your project is for.

    There are several ways to germinate seeds. If you germinate the seed in the dirt and pot, there is no need for transplanting. If you germinate in a paper then you do have to transplant but it may be faster to germinate.

    What’s the best way to germinate?


    You Will Need

    3 dixie cups
    6 paper towels
    paper dessert plates
    1/2 gallon distilled water
    Potting soil
    Small notebook and pencil
    Small paring knife (you will need an adult’s help with this part)
    6 seeds

    What to Do

    1. Add about two inches of potting soil to three cups
    2. Slice a small slice in the six seeds with the knife (ask an adult to help you with this) and plant three of them about ¼ inch deep in the cups with the soil.
    3. Take the other three seeds and wet the paper towels and place a seed inside them and then place each one on a plate.
    4. Water the soil, but don’t over water
    5. Place all the seeds in a room that is dark and quite warm and water as they begin to dry out. Make sure not to overwater and keep all the seeds in the same conditions. Keep them all in the same darkness and give them equal amounts of water so that your experiment offers good results.

    Monitor the state of the seeds daily. Note when they begin to germinate, which ones germinated first and which have the thicker and better stalk on the plants.. Note their growth rate in a week and in two weeks.

    Chart or graph the outcome and arrive at a conclusion that you can share with the other students.

    Ready for some additional information and experiments on Seed germination or gardening? Find out about the benefical insects that can live in your garden?

  • Make An Erupting Volcano Project

    Erupting Volcano


    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