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Diet Coke and Mentos Soda Geyser
The Diet Coke and Mentos soda geyser, also known as the soda and candy fountain or volcano, is a physical reaction between candy and carbon dioxide that instantaneously releases the gas so it shoots into the air. There is a lot of science behind this deceptively simple project! Here are instructions for performing the original project, tips for getting the tallest eruption, options for material substitutions, and a look at how the Diet Coke and Mentos geyser works.
All you need is a packet of Mentos candies and a 2-liter bottle of Diet Coke:
- Roll of Mentos candies
- 2-liter bottle of Diet Coke
Make sure the candy is fresh and the bottle of soda is unopened. Freshness matters!
You also need a way of delivering the candies into the soda. One method is just dropping the column from your hand, but rolling them into a paper or index card tube is more reliable. Stacking them into a test tube is another option.
Substitutions
While Mentos and Diet Coke work best, you have other options:
- Any carbonated beverage
- Any candy that stacks neatly into a column
- Coins, shot, or other small items that fit through the bottle opening
- Sand or salt instead of candy (which work quite well)
In general, diet carbonated beverages produce higher fountains than sugary ones. Also, they don’t produce a sticky mess. Uncarbonated beverages, like juice or water, do not work at all. Objects with smooth, flat surfaces (like coins) do not work nearly as well as other options.
How to Make the Diet Coke and Mentos Soda Geyser Erupt
The project is messy. You might want to step outdoors.
- Open the Mentos candies and stack them into a single column.
- Open the bottle of soda.
- Drop the column of candy into the bottle, all at once.
If you have more candy, you can repeat the eruption using the same bottle of soda. It won’t be quite as dramatic, but still works.
Tips for Getting the Biggest Eruption
- Diet Coke or other diet colas outperform any other drinks. There are a lot of potential reasons for this, mainly involving the effects of aspartame, potassium benzoate, and other ingredients on the surface tension and foaming capacity of the beverage. The worst carbonated beverages for this project are carbonated water and sparkling alcoholic drinks.
- The blue Mentos candies work better than other flavors. The fruity Mentos are reportedly the worst flavor. Freshly unwrapped candies are best. Old candy is not very effective, probably because humidity changes the candy surface.
- A 2-liter plastic bottle works better than any smaller bottle, whether it is plastic or glass.
- You get a better eruption at high altitude or low atmospheric pressure compared with sea level or other high pressure situation.
- Warm soda produces a higher fountain than cold soda.
How the Diet Coke and Mentos Experiment Works
The Diet Coke and Mentos eruption is a physical process more than a chemical reaction. The candy surface has many tiny imperfections and cavities, each only a micron or so in size. When you drop the Mentos into the soda there are numerous minute air bubbles stuck onto them. These little bubbles act as nucleation sites for rapid de-gassing of the soda:
CO 2 (aq) → CO 2 (g)
Because the nucleation sites lower the activation energy for bubble formation, you can say they catalyze the reaction.
The candies are dense enough that they sink to the bottom of the soda bottle, interacting with dissolved carbon dioxide as they fall. As carbon dioxide bubbles form, the gas is lighter than the liquid and the bubbles rise. As they rise, they expand. The pressure of the gas results in a quick release of pressure, making a geyser out of the soda. Ingredients in the partially-dissolved candy help the bubbles keep their shape and form a foam as the liquid ejects from the bottle.
Numerous investigations into why diet soda (especially cola) works better than sweetened soda or why Mentos works better than other candies answer some questions, but not all of them. The ingredients in the soda make a difference. However, which ones enhance bubble formation and which suppress it are unclear. The chemical composition of the candies likely contributes to bubble formation, but it’s really their surface structure that matters the most.
Turn the Science Project Into an Experiment
Performing the Diet Coke and Mentos project is easy, but turning the project into an experiment is also simple. Just find a variable under your control, predict the outcome from changing it, conduct an experiment that tests this hypothesis , and then analyze your results and see if your prediction was correct. Here are some ideas of variables you can explore:
- Is there an optimal number of candies for the best eruption?
- Compare different types of carbonated beverages. Do you think, for example, that Coke Zero performs as well as Diet Coke? Do other brands of diet cola perform as well?
- Explore the effect of soda temperature on fountain formation. If you see a difference, comparing chilled and warm soda, can you explain it ?
- Are there any candies that work as well as Mentos? In general, is there a way of predicting whether or not a particular kind of candy produces an eruption?
- What effect do you expect, if you add a bit of bubble solution or dishwashing liquid to the soda before adding the candy?
- Design different “candy delivery” systems. What are the pros and cons of each of them?
- Can you make a nozzle that reduces the diameter of the bottle? If so, what effect does this have on the height of the eruption?
Fun Facts About the Diet Coke and Mentos Project
- The original soda and candy fountain project, circa 1910, used Wint-O-Green Lifesaver candies (which as also great for the “spark in the dark” triboluminescence project ). However, the company changed the candy diameter in the 1990s and it no longer fits into most bottles.
- Scientists estimate the eruption releases between 2.4 and 14 million bubbles per liter of Diet Coke. Regular Coke produces a lot less bubbles.
- A single Mentos candy contains 50,000 to 300,000 nucleation sites, although the reaction does not utilize every one of them.
- Coffey, Tonya Shea (2008). “Diet Coke and Mentos: What is really behind this physical reaction?”. American Journal of Physics . 76 (6): 551–557. doi: 10.1119/1.2888546
- Kuntzleman, Thomas S.; Imhoff, Amanda M. (2021). “How Many Bubbles Are in the Foam Produced during the Candy-Cola Soda Geyser?”. Journal of Chemical Education . 98 (12): 3915–3920. doi: 10.1021/acs.jchemed.1c01001
- Kuntzleman, Thomas S.; Annis, Jezrielle; Anderson, Hazel; Kenney, Joshua B.; Doctor, Ninad (2020). “Kinetic Modeling of and Effect of Candy Additives on the Candy–Cola Soda Geyser: Experiments for Elementary School Science through Physical Chemistry”. Journal of Chemical Education . 97 (1): 283–288. doi: 10.1021/acs.jchemed.9b00796
- Kuntzleman, Thomas S.; Johnson, Ryan (2020). “Probing the Mechanism of Bubble Nucleation in and the Effect of Atmospheric Pressure on the Candy–Cola Soda Geyser”. Journal of Chemical Education . 97 (4): 980–985. doi: 10.1021/acs.jchemed.9b01177
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Fizzing Chemistry Experiment: Coke and Mentos Experiment
Categories Science Experiments
The Diet Coke and Mentos experiment is exciting to do for kids of all ages. We created this Coke and Mentos experiment lesson plan as part of our chemistry experiments for kids because it’s literally exploding with fizzing soda reactions and chemical changes!
But how exactly does the diet coke and mentos experiment work?
It all starts with two seemingly ordinary items—a bottle of Diet Coke and a roll of Mentos candies. When combined in a specific way, the coke and Mentos create a dramatic fizzing chemistry experiment that sends soda shooting into the air like a geyser.
Imagine witnessing a miniature volcanic eruption right in your own backyard!
The carbon dioxide in the Diet Coke and the bumpy surface of the Mentos candy are the key ingredients for this visually stunning display during the coke and mentos experiment lesson plan.
Table of Contents
Diet coke and mentos experiment lesson plan: the magic of the diet coke and mentos geyser.
The diet coke and mentos experiment lesson plan is a simple yet astonishing experiment that demonstrates the power of a chemical reaction in action.
With just a bottle of Diet Coke and a roll of Mentos candies, you can create a captivating eruption that surpasses expectations.
When the Mentos come into contact with the soda, a rapid release of carbon dioxide gas occurs, resulting in an explosive fizz.
The pressure builds up so quickly that the liquid is forcefully expelled in a powerful stream, creating the geyser-like effect.
How Does the Diet Coke and Mentos Experiment work?
The coke and mentos experiment lesson plan is a fascinating display of a chemical reaction in action and also that of a physical change causing a reaction between two ingredients.
When Mentos candies are dropped into a bottle of Diet Coke, it causes a rapid release of carbon dioxide gas, resulting in a dramatic eruption. But how does this reaction occur?
The reaction is primarily caused by two factors: the rough surface of the Mentos candy and the carbon dioxide gas dissolved in the Diet Coke.
The surface of the Mentos candy contains tiny pits and crevices, which provide numerous nucleation sites for gas bubbles to form.
When the candies are dropped into the soda, these nucleation sites allow the carbon dioxide gas to rapidly escape from the liquid.
The carbon dioxide gas in the Diet Coke is dissolved under pressure. When the bottle is opened or the candies are added, the pressure inside the bottle decreases.
This change in pressure triggers the gas bubbles to form on the rough surface of the Mentos. The gas bubbles rapidly expand, creating a fizzing effect.
As more and more gas bubbles are produced, the pressure builds up inside the bottle, eventually leading to an explosive release of the gas.
The liquid is forced out of the bottle in a powerful stream, creating the geyser-like eruption.
Is Fizzing a Chemical Change?
In fact, the reaction between the Mentos and Diet Coke is primarily a physical reaction rather than a chemical one.
The candy’s rough surface provides the necessary conditions for the gas bubbles to form quickly.
The process happens so rapidly that it creates a visually captivating and exciting reaction.
Supplies for a Diet Coke and Mentos Geyser
Here is what you’ll need to create this fizzing chemical reaction and complete your coke and mentos experiment lesson plan. These links are to Amazon or other affiliates of STEAMsational.
- STEM worksheet (click the image below to download)
Coke and Mentos Experiment Kits
Here are some alternative options for doing this fizzing chemical experiment and coke and mentos experiment lesson plan with a group of students.
- Classroom Geyser Pack (for 10 students)
- Steve Spangler’s Extreme Geyser Tube
- Observable Forces Classroom Bundle
If you love science and STEM but don’t like hunting for supplies, we love the Mel Science kits. They have options for elementary and middle school, and each kit comes with all the supplies needed for each experiment!
Diet Coke and Mentos Experiment STEM Extensions
Here are some STEM extensions you can add on to your coke and mentos experiment lesson plan.
Fizzing chemistry experiment variable exploration
Encourage students to experiment with different factors and observe their effects on the geyser. They can investigate elements such as the brand of soda, the size or shape of the candies, the temperature of the candies, or their surface roughness.
By systematically testing these variables, students can collect data and analyze how they impact the reaction. This exploration promotes critical thinking, hypothesis development, and data analysis skills.
Coke and mentos experiment lesson plan data analysis
Extend the experiment by incorporating data analysis and charting. Students can measure and record information from multiple trials, such as the height or duration of the geyser.
By organizing and graphing the data, students can visually explore the relationships between different variables, enhancing their mathematical skills and solidifying their understanding of scientific principles.
Geyser design engineering challenges
Introduce design engineering challenges related to the Mentos and Diet Coke Geyser.
Assign students the task of designing and building a device to control the force or direction of the geyser or develop a mechanism to initiate or stop the reaction.
This extension allows students to apply their knowledge of engineering, physics, and problem-solving to create innovative solutions.
Coke and mentos experiment science fair project
Encourage students to develop a science fair project based on the coke and mentos experiment lesson plan. They can formulate their own research question, design experiments to test their hypotheses, collect data, and present their findings.
Soda and mentos science project hypothesis: When Mentos candies are added to different brands of soda, the brand with the highest carbonation levels will result in the most significant eruption.
Based on prior knowledge and observations, the hypothesis predicts that the level of carbonation in soda will affect the intensity of the reaction when combined with Mentos candies.
Soda with higher levels of carbon dioxide gas dissolved in it will have a greater potential for gas release when the nucleation sites on the Mentos’ rough surface trigger bubble formation.
The with the highest carbonation levels is expected to produce the most substantial eruption when combined with Mentos.
More Chemistry Experiments to Try
Here are some other fun chemistry experiments that kids will love after you complete your coke and mentos experiment lesson plan.
- 15 Explosive and Awesome Chemistry Sets For Kids
- What is a Chemical Reaction for Kids?
- Chemical Reactions! How to Turn a Penny Green Experiment
- The Effect of Temperature on Reaction Time
How to Do the Mentos and Diet Coke Experiment Step by Step
The coke and mentos experiment lesson plan offers a tangible way for students to explore chemical reactions. Through firsthand observations, students can understand concepts such as nucleation sites, gas solubility, and the relationship between surface area and reaction rate.
This experiment also fosters critical thinking, logical reasoning, and problem-solving skills. Get the complete coke and mentos experiment lesson plan below!
Get the printable step-by-step directions for the coke and mentos experiment lesson plan below!
And don’t forget to use our free mentos and coke experiment worksheet that you can download by clicking the image below to complete your fizzing chemistry experiment!
Print a lot of papers? Get $10 your HP Instant Ink order when you use this link.
Diet Coke and Mentos Geiser
Looking for a simple and exciting science experiment? Look no further than the Diet Coke and Mentos experiment lesson plan! With just two ingredients and one worksheet, all you have left to do is teach the lesson!
- Paper towels
- Measuring tape
- Science notebook
Instructions
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