I know that peroxide reacts with metals and glass but why does it seem to react to organic materials more? If I pour it around my faucet it seems to bubble furiously around the crud around the base and not on the spigot itself. If I drop my earrings into some peroxide the whole earrings don't bubble only the "gunk" does and when that's gone it stops. When I pour it on a cut it bubbles but once it's clean it stops bubbling... Why? What is it about the "germs" or whatever that causes the reaction in peroxide? I mean it will bubble on a cut but not on my bare skin and it seems to be more reactive the ickier (I know that "ickier" isn't a word...Just stick with me here people!) the area it's poured on...
Now, THAT is what I call a challenging question! It requires some thinking in addition to the book-ish knowledge and I love it! But, before I continue with my answer, I'd just like to correct one statement:- "I know that peroxide reacts with metals and glass", It does NOT. Metals and glass act as catalysts i.e. they accelerate the reaction of conversion of Peroxide into Water and Oxygen but they don't participate in the reaction.
Now coming to your question, the varying levels of fumes that you are observing have nothing to do with an organic reaction.
Let's address all your situations one-by-one:
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1- When you pour it around the faucet and it bubbles furiously around the crud and not on the spigot itself.
The reaction going on in there is the same ol' Peroxide converting to Water and Oxygen.
One molecule of Peroxide (liquid) ----> One molecule of Water (Liquid) + Half molecule of Oxygen (gaseous)
Which is Symbolically-
H202 (l) -------> H2O (l) + (1/2)O2 (g)
It's just that the reaction takes place at a faster rate around the crud around the base!
In general, ANY rough surface acts as a CATALYST for this reaction. Try it yourself, put some peroxide on a smooth surface and then put some on a rough surface. You can easily see that it fumes and bubbles more on a rough surface. It is because on a rough surface there is more AMOUNT of surface on a given area due to all the unevenness of the surface. And more area accomodates more peroxide which leads to more reaction for a given area and hence a faster rate.
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2. When you drop earings into peroxide, the whole earings don't bubble only the "gunk" does and when that's gone it stops!
Hmm.. This required a little bit of thought process: The "gunk" in your earrings can be two things-
a) Deposition of Dust or dead skin-
If this is the case, then the answer would be- "Rough surfaces and dust CATALYZE the reaction of conversion of Perxide into Water and Oxygen which I have already motioned."
b) Deposition of METAL OXIDE because of rusting or corrosion or tarnishing of your earring.
Now, if THIS is the case, then the bubbles are coming out due to the REDUCTION reaction by peroxide in the acidic medium.
Let's see what's happening in there-
The Metal Oxide on the surface of your metal earrings is an oxidising agent i.e. it releases Oxygen (Oxygen atom). In presence of an oxidising agent, the Peroxide acts as a reducing agent. It reacts with the oxygen atom like this-
H2O2 (Peroxide) + [O] (Oxygen atom from the rust) -----> H20 (Water) + O2 (Oxygen molecule)
You can see that Oxygen is being released here, THAT CAUSES THE BUBBLES!
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3- It bubbles on cuts but, not on normal skin!
Whoa whoa whoa... Don't put it on your skin, the reaction of it's conversion to water is exothermic (gives out heat) and sometimes, explosive!
Now, to answer the question, it might be the tiny dust particles in your abrasion that could be triggerin' off the decomposition reaction & causing the release of Oxygen gas bubbles
OR as you might be knowing that the pH of the blood is MORE THAN 7, i.e. it is basic or alkaline in nature AND in alkaline solution, this reaction takes place-
Ferrous(Iron) Ions (Fe +3) + Peroxide (H2O2) + Hydroxyl Ions (OH-) ----------> Ferric (Iron) Ions (Fe 2+) + Water (H20) + OXygen Molecules
Did you see that? One of the products in the reaction up there was Oxygen molecules!! Now, that means that we are gonna have some bubbles there as Oxygen gas is gonna bubble baby!