How to Do the Mentos and Diet Coke Experiment: Step-by-Step Guide
The Mentos and Diet Coke experiment creates a tall foam jet by dropping mint Mentos candies into a 2-liter bottle of Diet Coke. You need a 2-liter bottle of Diet Coke, a pack of mint Mentos, and a way to drop all the candies in at once. The rough surface of the candy provides many sites for carbon dioxide bubbles to form quickly.
How the Reaction Works
The eruption is not a chemical reaction. The Mentos do not react with the soda to create new substances. Instead, the process is a physical one driven by nucleation.
The Role of Carbon Dioxide
Diet Coke is carbonated, meaning carbon dioxide gas is dissolved in the liquid under pressure. When you open the bottle, the pressure drops, and the gas wants to escape. Normally, bubbles form slowly on microscopic imperfections inside the plastic bottle. The Mentos candy provides a sudden, massive number of nucleation sites.
Why Mentos Work Best
Mint Mentos have a rough, porous surface covered with tiny pits. When dropped into the soda, these pits allow carbon dioxide molecules to gather and form bubbles very quickly. The gelatin and gum arabic in the candy also lower the surface tension of the liquid, making it easier for bubbles to grow and rise. A single Mentos can trigger thousands of bubbles per second.
Why Diet Coke Is Preferred
Regular soda works, but Diet Coke creates a more dramatic fountain. Aspartame, the artificial sweetener in Diet Coke, reduces surface tension more than sugar does. Lower surface tension means bubbles form and grow faster. Diet Coke is also less sticky than regular soda, making cleanup easier.
Step-by-Step Instructions
Follow these steps for a safe eruption. Work outdoors, away from buildings and people.
What You Need
- One 2-liter bottle of Diet Coke (room temperature works best)
- One standard roll of mint Mentos (about 14 candies)
- A piece of paper or cardstock to form a tube
- Safety glasses (recommended)
- A clear area outdoors
The Procedure
- Set up the bottle. Place the Diet Coke bottle on a flat, level surface outdoors. Remove the cap. Do not shake the bottle.
- Prepare the delivery system. Roll the piece of paper into a tube slightly wider than the Mentos candies. The tube should be long enough to hold the entire roll of candies.
- Load the candies. Hold the tube over the bottle opening. Drop all the Mentos into the tube at once. Do not let them fall one by one.
- Release and step back. Quickly pull the tube straight up so all the candies drop into the bottle at the same time. Step back immediately. The foam will shoot upward within one to two seconds.
A common mistake is dropping the candies in slowly or using a tube that is too narrow. If the candies get stuck, the reaction will be weak. For a consistent result, use a full roll of 14 Mentos and a 2-liter bottle of Diet Coke at room temperature.
Safety and Cleanup
The foam is mostly water, carbon dioxide, and sweetener. It is not dangerous, but it can stain clothing or surfaces. The liquid can also be slippery on pavement.
Precautions
Wear safety glasses to protect your eyes from foam spray. Do not drink the soda after the reaction, as it may contain small pieces of candy. Keep children and pets at a safe distance. The foam can travel several feet, so position the bottle away from walls, cars, and electrical outlets.
Cleaning Up
The foam will settle quickly. Rinse the area with a garden hose to remove sticky residue. The bottle can be recycled after rinsing. If any liquid gets on skin, wash with soap and water.
Variations to Try
Once you have mastered the basic method, you can test a few variables.
Temperature
Cold soda holds more dissolved carbon dioxide than warm soda. Try using a bottle of Diet Coke that has been refrigerated and one at room temperature. The room-temperature bottle will produce a taller fountain because the gas escapes more easily. The cold bottle will produce a slower, lower eruption.
Candy Type
Test different mint candies or fruit-flavored Mentos. Fruit Mentos have a smoother coating and produce a smaller fountain. You can also try crushed Mentos. Crushing the candies increases the surface area and can create an even more violent eruption.
Soda Type
Compare Diet Coke with regular Coke, Sprite, or seltzer water. Regular Coke has a higher surface tension due to its sugar content, so the fountain will be shorter. Seltzer water, which lacks the additives found in soda, produces a weak reaction. The combination of aspartame and carbonation in Diet Coke gives the best result.
Key Takeaways
- The eruption is a physical process called nucleation, not a chemical reaction.
- Mint Mentos work best because of their rough surface and ingredients that lower surface tension.
- Diet Coke produces a taller fountain than regular soda due to aspartame’s effect on surface tension.
- Always perform the experiment outdoors and wear eye protection.
- Room-temperature soda and a full roll of candies dropped at once give the most dramatic result.
