Dry ice color show
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The dry ice color show is a demonstration of the chemical formation of carbonic acid (H
2CO
3) by the dissolution of dry ice (the solid or frozen form of carbon dioxide – CO
2) in water (H
2O). The dry ice color show is usually performed in classrooms to demonstrate the properties of acids and bases, their effect on pH indicators, and the sublimation of dry ice. Setup is simple and generally involves only minor hazards, the main one being the low temperature of dry ice, which can cause frostbite upon skin contact. The carbonic acid formed in the demonstration is a weak acid and is not hazardous, being present in numerous consumer products including tonic water, soda, and beer.
This experiment demonstrates the properties of acids, bases, pH indicators, and the properties of carbon dioxide.[1] First, a large amount of universal indicator is added to water to facilitate the visual detection of changes in the solution's pH. Then, a few drops of ammonia (NH3) or sodium hydroxide (NaOH) is mixed into the solution, which changes the color of the solution; the type of pH indicator used determines which colors are seen.[1][2] Dry ice is subsequently added to form carbonic acid, changing the pH of the solution from basic to acidic.[2] This causes the solution to change colors again.[2][3] Simultaneously, a cloud of carbon dioxide is generated from the sublimation of dry ice due to the condensation of water vapor in the air.[4]