Make "Elephant Toothpaste" - The Decomposition of Hydrogen Peroxide

Uploaded by NurdRage on 20.08.2010

Greetings fellow nerds.
In this video we're going to do the classic demonstration of elephant toothpaste,
which is actually just a fast expanding foam.
To do this, start with 50mL of detergent.
If you can blow bubbles with it, it'll work.
Now we add to it 100mL of 30% hydrogen peroxide.
This peroxide concentration will cause burns so be careful when handling it, wear gloves.
Now mix it up.
Now we make a solution of potassium iodide by adding 10 mL of water
to 10 grams of potassium iodide and mixing it up.
When you're ready, just dump the iodide solution in and stand back.
And that is elephant toothpaste.
What's happening is the iodide ions react with the hydrogen peroxide
in a catalytic cycle to generate oxygen.
The reaction is really fast
and generates a massive foam because of the detergent.
A variation on the classic elephant toothpaste is to add about five grams of cornstarch
to the peroxide detergent mixture and shake it up.
This time the foam will change color with time.
This is because iodide slowly converts to triiodide
that the starch reacts with to create this purple iodine-starch complex.
The layers and swirls of color show that the iodide was not perfectly mixed
with the peroxide before it started.
This uneven distribution shows up as different colored patches.
Now potassium iodide isn't the only catalyst;
yeast for baking can also be used.
This is because it has an enzyme that decomposes hydrogen peroxide.
Just weigh out ten grams again and dissolve it in a minimum of water to form a suspension.
Now for this one we can add some fluorescent dye and make glowing elephant toothpaste.
I'm going to add some Fluorescein to this one to give it a green glow.
And now I’m going to add Rhodamine B on this other one to give it a red glow.
Okay lets mix those up.
Now we get the ultraviolet light and let them fluoresce.
Okay here goes with the yeast.
And that is glowing elephant toothpaste.
It's not as fast as iodide but it works.
I couldn't use potassium iodide because the triiodide produced
quenches the fluorescence and stops it from glowing.
Anyway, that was the classic demonstration of elephant toothpaste.
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