“Breath as a reagent” experiment
How to change a color of a solution just by a breath
Chemists are real magicians, only they have science on their side! They can show an interesting and spectacular experiment with a few reagents.
This experiment is safe. Care must be observed in working with phenolphthalein, it is a laxative. If the solution gets into the mouth, it must be rinsed out with water.
Reagents and equipment:
- calcium oxide (1 g);
- distilled water (300 ml);
- 1% phenolphthalein solution;
We dissolve calcium oxide in 300 ml of water. A diluted solution of calcium hydroxide is the result. Then we pour the solution into a flask and add a few drops of indicator, for example phenolphthalein. We put a straw in it and pass exhaled air through the solution. We observe the change in the color of the solution and the precipitation of a white sediment.
Calcium oxide easily dissolves in water with the formation of calcium hydroxide. The solution has an alkaline medium, as when the phenolphthalein indicator is added, the color changes to magenta. When the solution has exhaled air passed through it, which contains more carbon dioxide than the atmospheric air, the white sediment of calcium carbonate starts to precipitate, and the solution becomes colorless, as the medium becomes neutral, as calcium hydroxide turns into an insoluble carbonate.