I am a huge fan of all types of color changing potions that can grab kids attention and immerse them in chemistry at the same time. Previously we have made color changing juice that goes through a variety of colors depending on what you choose to mix into it. In this potion, we will be making a dark solution invisible. I love this project because you can find all of the ingredients at the drug store, and potentially in your house depending on how stocked your first aid kit is. Even better, you can use this solution with another easy to make solution to create a magical clock
How to make our Inuisibilitas potion
This potion is fun because as you add drops af the dark brown iodine in, they will turn clear. Cool right? First you need to make your base potion. To do this you will want to crush up four vitamin C tablets and dissolve them in water. You can do this by stirring the crushed tablets around for 30-60 seconds. If you want an ultra clear base potion you should filter this through a few coffee filters, which will pull out any remaining large chunks.
That’s it! You now have an inuisibilitas potion! Add a few drops of dark brown iodine and see what happens. How much iodine do you need to add to start changing the color of the solution brown?
How our Inuisibilitas potion works
This solution is making the iodine colorless through a chemical reaction. It turns out that iodine molecules are a dark brown color in water, but iodide ions are colorless in water.
How are we making iodide ions from iodine molecules?
We have two players in this chemistry experiment, vitamin C, and iodine. Vitamin C is also known as ascorbic acic, while iodine always comes in a pair (two iodine atoms attached to each other). When the ascorbic acid meets the iodine pair it splits them apart into two iodine ions (known as iodide). Of course, the ascorbic acid has to pay a price to split the ions apart, and it gives up two hydrogen ions as payment (a process known as oxidation). Without the two hydrogen ions, ascorbic acid just isn’t itself anymore, instead, it changed into dehydroascorbic acid.
So as we add iodine into our vitamin C solution we are changing the mixture from all ascorbic acid to ascorbic acid, dehydroascorbic acid, and iodide ions. Since the iodide ions are clear, and it fully reacts with the ascorbic acid we see the brown iodine disappear into clear. We can continue to do this until all of the ascorbic acid is converted into dehydroascorbic acid. Dehydroascorbic acid is poorer and can’t pay the two hydrogen ion fee to convert iodine molecules into iodide ions, which means the iodine will stay intact and be its normal brownish color.
What the chemical equation looks like
We can translate all of that into the following equations:
I2 + I- ↔ I3- (redox reaction)
C6H8O6 + I3- + H2O → C6H6O6 + 3I- + 2H+ (oxidation reaction)
Which takes up a lot less space!
Have extra Inusibilitas solution?
You can use your extra vitamin C – iodine mixture to create a color changing clock. Just make sure you don’t add too much iodine to your solution if you plan on doing this project too. I suggest adding 5-10 drops of iodine for every 1000mg of vitamin C you crushed up.