How to Do the Mentos & Soda Science Experiment

Overview

Dropping Mentos candies into a bottle of carbonated diet soda triggers a rapid release of carbon‑dioxide gas, producing a dramatic fountain (or “geyser”). The effect is caused by the rough surface of the Mentos providing nucleation sites where bubbles form quickly ¹².

Materials

• 1 × 2‑liter bottle of diet soda (e.g., Diet Coke) – carbonated and chilled
• 1 × roll of Mentos (original flavor works best)
• Simple dropping device: a paper towel roll, a small tube, or a DIY holder (optional)
• Safety glasses (optional but recommended)
• Open area: backyard, driveway, or a sink to contain the splash

Procedure

Option A – Classic “Tube” Method (quick drop)

1. Prepare the bottle – Open the soda slowly to release excess pressure; set the bottle upright on a flat surface.
2. Load the Mentos – Place 5‑7 Mentos into a paper tube (or similar holder). Some sources suggest 3‑5; both ranges work, but more candies give a taller geyser.
3. Seal (optional) – Some demonstrators tape an index card over the tube’s end to keep the Mentos together until release.
4. Drop the Mentos – Quickly remove the card (or simply tip the tube) so the Mentos fall into the soda in a single burst.
5. Step back – Observe the rapid eruption and enjoy the fountain.

Option B – “Tilt & Pour” Method (reduces pre‑formed bubbles)

1. Open the bottle – As above, open slowly.
2. Tilt the bottle – Hold the bottle at a slight angle and pour the soda down the inner wall. This minimizes existing bubbles, allowing a larger geyser when Mentos are added.
3. Add Mentos – Hold 3‑5 Mentos in your hand (or a small holder) and drop them in one swift motion.
4. Observe – A sudden burst of foam shoots upward.

Both methods rely on the same physics; choose the one that feels easiest for your setup.

Why It Works

• Nucleation sites: The porous surface of Mentos provides millions of tiny cavities where dissolved CO₂ can rapidly form bubbles.
• Rapid gas release: The sudden bubble formation creates a large pressure surge, forcing liquid out of the bottle as a geyser.
• Diet soda advantage: Lower sugar content reduces surface tension, allowing bubbles to grow faster and higher.

Safety & Cleanup

• Perform the experiment outdoors or over a sink to avoid mess.
• Wear safety glasses to protect eyes from splashing soda.
• Do not look directly into the bottle when the Mentos are released.
• After the eruption, discard the soda and Mentos, then wash the area with soap and water.

Variations & Extensions

• Try different sodas (regular Coke, Mountain Dew, etc.) to compare geyser heights.
• Use flavored Mentos or other candy with varying surface textures.
• Measure the height of the geyser with a ruler or video analysis for a quantitative study.

For detailed videos and additional tips, see the ACS guide, Science Buddies activity, and several YouTube demonstrations ¹²⁵⁸.