The Diet Coke and Mentos reaction is a common experiment performed in many science classes. This year, I adapted my somewhat free-wheeling “wing it” approach to this experiment to instead have students research, test, and adapt as needed. The students’ goal is to get the highest possible geyser. When analyzing my new approach to this time honoured experiment, I determined the following:
Pro:
- Many groups performed many trials to test their ideas;
- Students learned that what happens in a test isn’t always what happens in reality (i.e. even though a certain way may have worked during the test phase it may not necessarily work as planned on launch day);
- The engineering components of building devices to, hold the bottle in place and, the means by which students were able to physically get the mentos into the bottle were varied. It was exciting to see the innovative approaches taken here.
Con:
- Human nature is generally lazy if allowed to be so. As such, there were some groups that did predictably little research, conducted very few tests, and, on the day of launch, merely dumped the mentos into the bottle and hoped for the best. In future, I will be sure to adapt the marking scheme to reflect that when due diligence and testing is performed such is reflected in a much better grade.
- There were a few ideas that were ingenious but came perilously close to breaking the rules! I decided to not be the judge of such matters solely by myself but instead created the ad hoc “IUPAC Diet Coke and Mentos Division.” This consists of a group of science teachers who discuss and vote whether the different ideas were suitable or not.
- Teachers’ note: make sure your electrical outlets are working properly: with so many kettles and thermal blankets turned on, my very old chemistry room blew all the fuses with astonishing alacrity
I spend three class periods on this activity. My class periods are 75 minutes long.
On launch day, each lab group will receive only 1 2-L bottle of Diet Coke and 1 package of Mentos (original flavor).
For students’ test phases, it is up to them to obtain their own supplies. We are lucky at our school to have a fund for students in financial need--I use my discretion, where applicable.
Logistics:
- Students complete a pre-lab set of questions on the experiment in general (e.g. what is nucleation?)
- Students complete a pre-lab quiz on safety – all have to obtain a perfect score before launch day.
- Students submit their procedure at least a day before the launch. If a change in procedure occurs after same was checked by the teacher, the group automatically loses 50% of their grade for this component of the marking scheme. This is to prevent the “lemming” (aka copycat) effect on launch day.
- I supply the Diet Coke and Mentos for the launch day but during the students’ test phases, it is up to them to obtain their own supplies. We are lucky at our school to have a fund for students in financial need--I use my discretion, where applicable.
- For marking purposes (besides answering the questions embedded in the lab) if students create a geyser, they receive 10/10 and 1st place (aka highest height) garners 3 additional marks; 2nd place, an additional 2 marks; and 3rd place, a single additional mark. One may also set thresholds of height for marks if desired. Indeed, this may be an avenue I pursue in future because it would be great to link height thresholds directly to grades.
The following is the lab I used with the students. You can download the Student Document here: 
The Diet Coke And Mentos Reaction (A Word Document is also available in the Supporting Information. Readers must be logged into access the Supporting Information.)
The Diet Coke And Mentos Reaction
Purpose: The purpose of this experiment is to use gas laws, ingenuity, and a bit of luck to create the biggest soda fountain geyser possible when Diet Coke and Mentos are used in combination.
Waste Disposal:
- Return the 2L bottle with the cap to the teacher. This too will be worth marks. [As an aside – I use the 2L bottles for a Rocket Lab I do in the Mole Unit]
- Be sure to clean up the collateral mess made outside during the launch.
Special Safety: Be sure all persons are suitably clear of the geyser during launch.
Video 1: The Science of Diet Coke and Mentos, Tommy Technetium YouTube Channel, August 2020.
Pre-lab:
1. Watch Video 1, and be able to answer the following:
a) How is the geyser created in a Diet Coke and Mento’s experiment?
b) How can the chemical reaction be shown?
c) Is what you observe a physical or chemical change? Explain your answer.
d) What is the chemical equation for carbon dioxide dissolved in water?
e) Is carbonated water acidic or basic?
f) What happens to the pH when mentos are added to the carbonated water?
VIDEO 2: Diet Coke & Mentos | MythBusters | Discovery YouTube Channel
2. Watch Video 2 and be able to answer the following:
a) What is nucleation?
b) What happens at the nucleation site?
c) What does a Mento look like close up?
d) What forms at the surface of a Mento (in a very short period of time?)
e) Why does a fountain or geyser form?
f) What is the control used in the video? [Do you remember what a control is?]
g) What does a coloured Mento have in contrast to say a white Mento?
h) What happens when a coloured Mento is placed in carbonated water?
Video 3: Diet Coke and Mentos at Different Temperatures, Tommy Technetium YouTube Channel, May 2017.
3. Watch Video 3 and be able to answer the following:
a) How does temperature affect the reaction of carbonated water and mentos?
b) What is the maximum temperature used in the experiment? Show your answer in both °C and K.
Planning for the experiment:
Logistics:
- Order of launch for each lab group will be chosen randomly.
- Everyone will be required to be outside for all launches.
- The launch will take place at the side of the school outside the classroom.
- No objects are permitted to remain on the top of the Diet Coke bottle before or during the launch.
- The bottle or cap cannot be altered in any way from its original form.
- The diet coke bottle must remain on the ground for the launch.
- On launch day, lab groups will receive only 1 bottle of Diet Coke and 1 package of Mentos. No exceptions.
- Lab groups will have 15 minutes to prepare for launch.
- Any components used for the launch day must be homemade (e.g. a device to hold the container in place or a device used to get the Mentos into the Diet Coke bottle.)
- To participate, a group must have its procedure sent in and checked by the teacher. No group is permitted to change its procedure on the day of the launch.
- Students should NOT dress in their finest clothes on launch day.
- While failure is not the desired option, one will learn on launch day that fate and circumstances sometimes cause failures to occur.
The following is needing to be researched and discussed with one’s lab group before testing begins. The goal is to get as high a geyser as possible. Suggested areas of intra-group discussion may include:
- Diet Coke – changes to be made.
- Mentos – changes to be made.
- Are there any homemade devices to be made to facilitate the process?
- What is everyone’s role on launch day?
- Other?
Materials:
Groups shall list ALL equipment and chemicals (consumable goods) needed for the experiment.
Procedure:
Groups shall provide a detailed explanation of the procedure each will be following. Be sure to write using third person and in the past verb tense.
ALL GROUPS MUST HAND-IN THEIR MATERIALS AND PROCEDURE
AT LEAST ONE DAY BEFORE LAUNCH DAY!
Observations:
Groups shall include all observations made before, during, and after the launch.
Results:
Groups shall:
a) Explain generally how their launch went.
b) What worked with their launch?
c) What did not work with their launch, and list known and potential unknown reasons why?
d) Which group was the best? Explain. [Please do not use your lab group as an example!]
e) Which group was the least successful? Explain. [Please do not use your lab group as an example!]
Video 4: Speedy Science Clips: How does altitude affect Diet Coke and Mentos? Tommy Technetium YouTube Channel, February 2020.
Watch Video 4 and be able to answer the questions:
a) What happens to air pressure as elevation increases?
b) Complete the following chart:
c) Using the information supplied in the chart above, graph the following:
i) Pressure vs Volume (volume on the horizontal axis)
ii) Pressure vs 1/average volume (1/volume on the horizontal axis)
d) i) What relationship is shown between pressure and volume?
ii) What relationship is shown between pressure and 1/volume?
Video 5: Coke and Mentos at 14000 Feet, Tommy Technetium YouTube Channel, September 2018.
Application:
Watch Video 5 and be able to answer the questions:
a) Using the video and the graph shown to the right, identify the overall trend in the volume of the geyser as elevation increased (and air pressure decreased).
b) Explain what might be the cause of the anomalies (i.e. dips) in data?
c) If these scientists were to do this experiment again, what changes should they make?
Above and Beyond:
Create a report/document that explains further experiments that perhaps ought to be performed in regard to diet coke and mentos to produce better results. This is an opportunity to demonstrate your intelligence, creativity, and “outside the box” thinking.
Obtain materials and arrange for area outside to complete experiment.
- I thank Tom Kuntzleman for his patient guidance and meaningful suggestions when writing this lab.
- I thank Avery Orlik for drawing the wonderful picture for this lab. Avery is incredible at both chemistry and art!
- I thank Matthew Clifford for always editing my work!
- IUPAC Symbol (from the membership card) Citation: International Union of Pure and Applied Chemistry (IUPAC). International Science Council. (2022, February 25). Retrieved December 27, 2022, from https://council.science/member/international-union-of-pure-and-applied-c...
- Video - DiscoveryNetworks. (2008, July 31). Diet Coke & Mentos | Mythbusters. YouTube. Retrieved December 23, 2022, from https://www.youtube.com/watch?v=LjbJELjLgZg
- Video - TommyTechnetium. (2017, May 7). Diet Coke and Mentos at different temperatures. YouTube. Retrieved December 23, 2022, from https://www.youtube.com/watch?v=dHrRudxIVeA
- Video - TommyTechnetium. (2018, September 24). Coke and Mentos at 14000 Feet. YouTube. Retrieved December 23, 2022, from https://www.youtube.com/watch?v=NyUW0hXYGnU
- Video - TommyTechnetium. (2020, February 27). Speedy science clips: How does altitude affect diet coke and mentos? YouTube. Retrieved December 23, 2022, from https://www.youtube.com/watch?v=SWpgRBr85PA
- Video - TommyTechnetium. (2020, August 26). The Science of Diet Coke and Mentos. YouTube. Retrieved December 23, 2022, from https://www.youtube.com/watch?v=-cN5mCorP5E
Safety
General Safety
General Safety
For Laboratory Work: Please refer to the ACS Guidelines for Chemical Laboratory Safety in Secondary Schools (2016).
For Demonstrations: Please refer to the ACS Division of Chemical Education Safety Guidelines for Chemical Demonstrations.
Other Safety resources
RAMP: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies
NGSS
Analyzing data in 9–12 builds on K–8 and progresses to introducing more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data.
Analyzing data in 9–12 builds on K–8 and progresses to introducing more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data. Analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution.
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of a design.
Scientific questions arise in a variety of ways. They can be driven by curiosity about the world (e.g., Why is the sky blue?). They can be inspired by a model’s or theory’s predictions or by attempts to extend or refine a model or theory (e.g., How does the particle model of matter explain the incompressibility of liquids?). Or they can result from the need to provide better solutions to a problem. For example, the question of why it is impossible to siphon water above a height of 32 feet led Evangelista Torricelli (17th-century inventor of the barometer) to his discoveries about the atmosphere and the identification of a vacuum.
Questions are also important in engineering. Engineers must be able to ask probing questions in order to define an engineering problem. For example, they may ask: What is the need or desire that underlies the problem? What are the criteria (specifications) for a successful solution? What are the constraints? Other questions arise when generating possible solutions: Will this solution meet the design criteria? Can two or more ideas be combined to produce a better solution?
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories. Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models.
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models. Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.
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Comments 1
Mentos Diet Coke
This sounds like a great lab for our Earth Day celebration, our entire school have classes outside to celebrate Earth Day.