For young students being exposed to the mysteries of chemistry for the first time, the laboratory can be a daunting place. The blue bottle chemistry experiment is often a good first exposure to basic chemical reactions. The goal is simple enough. Based on a chemical reaction, solutions in a flask are shaken until the originally clear liquid turns blue. Upon being allowed to settle out again, the solution returns to its previous clear state. This experiment demonstrates one of the basic reactions of chemical solutions.
The materials needed for this experiment are simple and commonplace. Before beginning the experiment, gather the following short list of items:
* Two flasks with rubber stoppers
* A beaker of tap water
* 7.5 grams glucose
* 7.5 grams sodium hydroxide
* 2 ml methylene blue solution
Fill the flasks to the half way point with water. Add 2.5 grams of the glucose to the first flask; the remainder goes into the second flask. Add 2.5 grams of the sodium hydroxide to the first flask; again, the remainder goes into the second flask. Divide the methylene blue solution equally between each flask.
Use the rubber stopper to seal the flasks. Shake the contents thoroughly. The solution in each flask will turn blue. Place the flasks on the rack to settle out. The solution will return to its previous clear state. This reaction is caused by the oxidation process. If the flasks are shaken again, the solution will return to its blue color. The blue color will disappear as soon as the flasks are allowed to rest undisturbed.
The second flask, which contains twice the concentration of the solution as the first one uses the dissolved oxygen twice as fast as the first flask. As a result the blue color will disappear twice as fast in the second flask as in the first. All that remains is a blue ring around the surface of the water, the result of the oxygen mixing with the open air space in the flask.
Even though this is a simple experiment with common ingredients, care should be taken at all stages during the experiment. Sodium hydroxide is a corrosive agent. It can cause serious eye injury. Gloves and safety goggles are a good idea here, as with any experimentation involving chemicals.
The goal of this experiment is to teach the principles of reaction kinetics, the effects of physical or chemical change brought about by outside forces. For students in the early stages of scientific study, it is a clever and engaging activity and will provide good groundwork for future experiments.
