When dry ice is added to indicator solutions, the solid carbon dioxide sublimates, producing bubbles and fog that look like boiling. As carbon dioxide dissolves in water, it forms carbonic acid, lowering the pH and causing the indicator solutions to change color dramatically from their basic to acidic forms.

1. Set out five 1-L beakers filled about three-quarters full with water.
2. Add 2 mL of a different indicator solution to each beaker (bromcresol green, universal indicator, phenol red, methyl red, bromthymol blue).
3. Add a small amount of ammonia dropwise to adjust each solution so it starts in its basic color range.
4. Prepare five smaller beakers (100 mL each) as reference solutions by transferring some liquid from each large beaker.
5. Wearing insulated gloves, place a nugget of dry ice (about the size of a walnut) into each of the five prepared beakers.
6. Observe vigorous bubbling, fog formation, and color changes as carbon dioxide dissolves and the solutions shift to acidic colors.

Dry Ice Color Show - FlinnScientific:

Dry Ice Rainbow of Colors - FlinnScientific:

📄 Dry Ice Color Show- FlinnScientific: https://www.flinnsci.com/api/library/Download/eb185d0fe3b6425094eb97f6546dbcda?srsltid=AfmBOopYnzYwotMoh52ykLgsvbF3rhFBjJidTdKSpgvp2q3HU0mc2y1S

• Use different indicators to expand the range of colors demonstrated.
• Compare the rate of color change with larger vs. smaller dry ice pieces.
• Try the experiment in warm vs. cold water to observe changes in sublimation rate.

• Always wear chemical splash goggles, gloves, and a lab apron.
• Handle dry ice with insulated gloves—never touch with bare skin (risk of frostbite).
• Work in a well-ventilated area since carbon dioxide gas can accumulate.
• Ammonia is irritating; avoid inhalation of fumes.
• Dispose of solutions according to lab safety guidelines and allow unused dry ice to sublimate in a ventilated area.

• Why does the solution appear to “boil” when dry ice is added, even though it is not hot?
• What chemical reaction occurs when carbon dioxide dissolves in water?
• How does the pH change explain the color shifts in the indicators?
• How does this demonstration help explain natural processes like ocean acidification?