Diet Coke and Mentos Eruption

Love explosive science experiments? The Diet Coke and Mentos eruption is sure to thrill kids and adults alike! This fun and fizzy activity is a perfect example of a physical reaction rather than a chemical reaction. Learn how the combination of Mentos candy and a bottle of Diet Coke creates an exciting eruption of foam!

Diet Coke and Mentos Rocket Experiment

Science Concepts Explored:

Physical Changes: Understanding how the state of matter changes from liquid to gas.
Surface Tension: Learning how gas bubbles are trapped in liquid and how this tension is broken.
Carbon Dioxide: Exploring how carbon dioxide gas in carbonated beverages causes fizz and foam.

Grade Level: This experiment is great for Grades 3-6, but younger kids (Grades K-2) can also enjoy the hands-on experience with some adult supervision.

Supplies:

2 2-liter bottles of Diet Coke (or your preferred carbonated beverage)
Mentos candy
2 index cards
Blue Painter’s Tape
String
Eye Protection
Measuring Tape

How to Set Up the Diet Coke and Mentos Experiment

💡 This experiment is best done in an outdoor area! If you want to experiment and take measurements, try it against an exterior wall of a building and use the blue painter’s tape to record the height of the spout. 🛑 Make sure to move away a safe distance and wear eye protection!

Step 1: Create the Mentos Delivery Tube

Roll up an index card into a tube and secure it with tape. The tube should be large enough to hold whole Mentos candies but small enough to allow them to fall out easily. Have kids measure the diameter of a Mentos candy for an extra math challenge.

Step 2: Attach the Tube to the Bottle

Tape the tube to the top of your bottle of Diet Coke, leaving one side open. This allows you to easily slide an index card underneath to release the Mentos when the time comes.

diet coke and mentos paper tube, DIY mentos cartridge

Step 3: Set Up the Trigger System

Place the second index card underneath the tube. Attach a piece of string to this card using tape.

Step 4: Drop the Mentos into the Tube

Place the Mentos candy into the tube and prepare to trigger the eruption.

Step 5: Step Back and Pull the String

With the string in hand, step back and pull the string, which will release the index card and cause the Mentos to drop into the Diet Coke. Watch the eruption in action!

💡 Tip: Use a tape measure or mark a wall with tape to record the fountain height (the height of the eruption). For an extra touch, use your camera’s slow motion function to capture the peak height more easily.

How Does the Reaction Work?

Inside Diet Coke (or any carbonated beverage), there is dissolved carbon dioxide gas. This gas creates gas bubbles, which give soda its characteristic fizz. Typically, the gas is trapped by surface tension in the soda, keeping it in its dissolved form.

When you add Mentos to the bottle of soda, the rough surface of the candy accelerates the release of gas. As more gas bubbles form on the Mentos’ surface, they push the liquid out in an explosive eruption, converting the dissolved carbon dioxide gas into a rapidly expanding gas. This is a physical reaction as the state of the gas changes, but no new substances are formed.

💡Did you know you can try this experiment with other candies and even pennies? That’s because it’s a physical change instead of a chemical one! Go ahead and experiment!

finish of the diet coke and mentos eruption

Why Diet Coke Works Better Than Regular Coke?

You might be wondering, Why do we use Diet Coke over regular Coke for this experiment? The answer has to do with the ingredients and the way Diet Coke reacts with Mentos.

Regular Coke contains sugar, while Diet Coke uses an artificial sweetener called aspartame. While both sodas contain carbon dioxide gas dissolved inside, which creates the bubbles and fizz, Diet Coke has a slightly different composition because it doesn’t contain sugar.

Here’s where it gets interesting: Aspartame, the sweetener used in Diet Coke, facilitates the formation of bubbles more easily when Mentos are added. The Mentos create tiny bumps on the surface, which act as places for the carbon dioxide to escape quickly. Because Diet Coke doesn’t have sugar, the bubbles can escape more freely, creating a bigger and faster eruption.

💡 Fun Fact: The sugar in regular Coke can make the soda more viscous (thicker), which slows down the formation of bubbles. This is why the Mentos eruption is often larger and faster with Diet Coke, as it allows the bubbles to escape more easily.

How to Apply the Scientific Method to Your Experiment

The Diet Coke and Mentos eruption is an excellent opportunity to apply the scientific method. Here’s how you can approach the experiment:

Form a Hypothesis: What do you think will happen when you drop Mentos into Diet Coke? Will it erupt faster with more Mentos or a different soda? Try changing the size of the Mentos or experiment with different types of soda, such as orange soda, Sprite, or club soda.
Variables: Change one thing at a time, such as the type of soda, the Mentos flavor (like mint or fruit Mentos), or the temperature of the soda. Measure the height of the eruption to test your hypothesis.
Test: Drop the Mentos candy into the soda and observe what happens.
Conclusion: Did your hypothesis match the outcome? Write down your observations!

💡 Tip: For older kids, experiment with multiple trials to see how different factors—such as soda temperature, candy size, or type of soda—affect the eruption.

Expanding the Mentos and Diet Coke Experiment

1. Experiment with Crushed Mentos

Try crushing the Mentos into small pieces before adding them to the soda. Does the size of the Mentos affect the height of the eruption or speed of the reaction?

2. Test Different Soda Flavors

Does Diet Coke create the biggest eruption, or does regular Coke, Root Beer, or Sprite make a higher fountain? Experiment and find out! What about Diet Pepsi or a generic brand of cola?

3. Try Soda at Different Temperatures

What happens when you use cold Diet Coke versus room temperature? Does temperature change the eruption?

4. Test Different Kinds of Candies

Can you replace Mentos with something else? Try other candies like mint or fruit-flavored Mentos, or even pennies or rock salt, and observe if they create the same effect.

Mentos and Diet Coke Science Fair Experiment

This experiment is not only fun but perfect for a science fair project! Kids can use the scientific method to test variables, formulate a hypothesis, conduct trials, and present their findings. It’s an excellent way to practice presenting data and conclusions.

💡 Need help with your science project? Check out our Easy Science Fair Projects and Science Fair Tips to make sure your project stands out!

More Fun Science Projects to Try

If you love this Diet Coke and Mentos eruption, try these exciting science experiments:

💡 Bonus: Get our full Science Project Pack, featuring over 300 pages of hands-on experiments, printables, and more! Perfect for creating fun and educational science projects!