Science Focus: Gas release, nucleation sites, chemical reactions

Objective

Students will observe how carbon dioxide gas escapes from a carbonated beverage and learn how “nucleation sites” help gas escape rapidly.

Materials

1 large (2-liter) bottle of carbonated soda (any brand)
A clean, unused soda bottle cap
Peppermint Lifesavers or similar mints with holes
Thread or fishing line
Tape
Nail or thumbtack
Pliers (for holding the nail)
Optional: candle or lighter to heat the nail if melting the hole
- Alternatively, a hammer and nail can be used instead of fire.

⚠️ Safety Notes

This experiment creates a large soda fountain—do it outdoors.
Keep students several feet back from the bottle.
Remove or modify any step involving heat if working with young children.
Teachers may pre-prepare the special cap ahead of time.

Plan

1. Prepare the Special Bottle Cap

(Teachers should do this step.)

Use pliers to grip the nail.
Warm the point for a few seconds OR simply push the nail through the cap using pressure (no heat needed).
Create a small hole in the center of the soda cap.
Set aside to cool if heat was used.

2. Prepare the Mint Dropper

Tie a mint onto one end of the thread.
Add 3–4 more mints like beads.
Feed the loose end of the thread up through the hole in the bottle cap.
Pull the mints tightly against the underside of the cap.
Use a piece of tape on top of the cap to hold the thread in place.

Now the mints hang just inside the cap and won’t touch the soda until the thread is released.

3. Activate the Soda Fountain

Take the soda bottle outside.
Set it on stable ground.
Remove the regular cap.
Screw on the special “mint cap,” making sure the mints are held above the liquid.
Hold the thread, remove the tape, and step back.
Drop the thread—allowing the mints to fall into the soda.
Quickly move away and watch the soda fountain shoot upward!

A powerful jet of soda may spray 15–20 feet into the air.

What’s Happening? (Kid-Friendly Science)

1. Soda Contains Carbon Dioxide

Soda is fizzy because carbon dioxide gas is dissolved inside the liquid under pressure.

2. Mints Have Very Rough Surfaces

If you look at a mint under a microscope, you’d see:

tiny pits
cracks
holes

These rough spots trap microscopic air bubbles.

3. When the Mints Touch the Soda

Each tiny pocket of air becomes a nucleation site—a starting point where carbon dioxide rapidly gathers.

Thousands of bubbles form at once.

4. Bubbles Need Space to Escape

Because the cap has a small hole:

gas escapes upward
liquid is pushed with it
causing a dramatic soda geyser

Try This Too! (Safe Variations)

A. Ice Cream + Soda

Adding ice cream to soda also creates nucleation sites on the ice cream surface.
This makes foam—also known as a float.

B. Compare Mints

Try:

Lifesavers
Mentos
Sugar cubes
Sand
Salt
Which creates the biggest fountain?

C. Temperature Test

Do warm sodas produce bigger reactions than cold sodas?

Teacher Notes

This experiment introduces:

physical vs chemical changes
solubility of gases
pressure release
real-world examples (shaken soda bottles, fireworks fountains, volcanic vents)

It works well outdoors during:

end-of-year parties
science fairs
family science night

Soda Fountain Nucleation (Mentos in Soda Experiment)