Summary: Solid carbon dioxide is added to a large beaker of water containing universal indicator. As the CO2 dissolves, the indicator changes from neutral (green) to acidic (orange).
Dry Ice is extemely cold, use gloves or tongs when handling.
Chemicals and Solutions:
universal indicator solution
2 lbs. dry ice
25 mL of 0.l M NaOH solution
6 M NaOH solution
4 liter beaker of water
Add univeral indicator solution to the water and make the solution purple by adding some 0.1 M NaOH solution. Then just start adding dry ice to the solution. The dry ice will sublime causing the solution to bubble and it will also dissolve in the water forming carbonic acid causing the indicator to change colors as the solution becomes more and more acidic. The solution will change from purple to blue to green to yellow to orange and finally to red. Once the red color is reached 6M NaOH can be added to take the color back up to purple and the cycle can begin again.