An excellent, yet simple, experiment for elementary students, the blue bottle chemistry experiment is used to demonstrate reactions between certain chemicals. When this experiment is executed properly, a blue solution, inside a clear glass bottle, gradually becomes clear when left to sit. When the bottle of liquid is swirled around, the solution becomes blue again.
Necessary materials to perform the demonstration:
500 ml of tap water
one 1-liter glass container with a stopper
10 g glucose
10 g sodium hydroxide, NaOH
1 ml 0.1% solution of methylene blue
Safety goggles that fit
An apron, preferably plastic
Non-latex plastic or rubber gloves
A plastic table cloth to cover the surface you’re working on.
Tips for setting up before the class:
Before you begin your experiment, make sure all your containers, measuring cups and spoons, are completely free of dirt, dust, debris and lint. These items can cause an experiment to go awry.
For all materials that need to be weighed and measured for this experiment, weigh and measure ahead of time. Double check your numbers. Place each pre-weighed and pre-measured material in its own marked glass container. For very small amounts, you can use a shot glass. This will help keep the experiment moving along and avoid student boredom.
Place the tablecloth on the demonstration table or desk. Place all the materials, goggles, gloves and aprons out on the tablecloth.
Directions for performing the experiment:
Pour 500ml of water into a 1 liter container.
Add a heaped teaspoon (approximately 10 grams) of sodium hydroxide and dissolve by swirling.
Add two level teaspoons (approximately 10 grams) of glucose and dissolve by swirling.
Add 3-4 drops of methylene blue. Place the stopper or cork firmly in the top of the bottle. Swirl the mixture and stop. The liquid should appear blue.
Let the solution quietly sit for a while and it should become clear.
Give the glass bottle a few gentle shakes so that air dissolves in the solution. If you are using a cork or stopper, check that it is on properly and take special care not to spill any liquid.
Again, the color will change to blue.
Let the bottle sit again and the solution will turn clear again over a short period of time.
The more often you shake the bottle, the longer the blue color will take to fade.
The process can be repeated for over 20 times. You may have to allow more air into the bottle if you are using a container with a cork or stopper. After some hours, the solution will turn yellow and the color changes will fail to occur.
Tips for performing this experiment:
Always properly wear personal protective devices, safety goggles, aprons and rubber/plastic gloves when working with chemicals. Put on all PPD before you begin working or handling chemicals.
Make sure you use a glass with a cork or rubber stopper. This will allow you to gently shake the bottle or glass without spilling it’s contents. Keep your thumb over the cork or stopper to keep it from falling out while gently shaking or swirling the bottle. Finding it hard to find a glass bottle with a cork or stopper? Try using a clean clear 1 – liter wine bottle. Tear off the label and clean off any remaining glue for better visibility. Sometimes the housewares section of your favorite store will have oil and vinegar bottles with glass, cork or rubber stoppers.
Glucose powder works best for this type of experiment. If you’re using the tablet form, cradle two metal tablespoons, one on top of the other. Place a tablet in the bottom spoon’s bowl, between the two spoons. Apply pressure to crush the tablet between the two metal spoons.
Supermarkets carry products used to unblock kitchen or bathroom drains. Some of these products use the ingredient Sodium Hydroxide as their only active ingredient. Be sure to read the labels.
You should be able to find Methylene blue at your favorite local pet store. This chemical is traditionally used as a medication for freshwater aquarium fish. Be sure to read the labels.
Use the time waiting for the blue water to turn clear to explain the process and experiment. Make sure the bottle is not being agitated or shaken during this time or it will lengthen time time needed for the reaction to happen.
Cleaning up by wrapping up all your plastic trash inside the plastic tablecloth. Throw the plastic tablecloth into a recycle bin. The chemical reaction neutralizes the caustic chemical, sodium hydroxide, so it is safe to pour the experiment down a sewer drain or a septic drain. When you pour the water into a sink drain or toilet, make sure you thoroughly flush with water afterward.
DO NOT reuse the glass bottle for anything else. If you are going to reuse this bottle for a similar experiment, rinse it out well, then wash it and let it air dry. Mark it “blue bottle experiment only”. Place it out of reach of children. If you’re not going to use this bottle again for a similar experiment, rinse out the bottle, let it dry and then throw it in the recycle bin. Always wear rubber gloves when rinsing and washing out bottles. Throw rubber gloves away when you are done.