I understand that yeast, or bleach, or even light, can cause peroxide to break down into water and oxygen. Something in the yeast, or the bleach acts as a catalyst and juggles the peroxide into parting with the extra oxygen. And the energy of light can do that. But what, exactly, does yeast or bleach do in that reaction, and what is it in cuts and abrasions that stimulates the same reaction? Thanks, xo, C.
Similar thread that asks “What is actually causing the peroxide to foam?”
There are two threads to the answer.
Bubble tend to form on broken surfaces (think beer in a glass). This is because to form a bubble in liquid take energy to break apart the liquid. So to have half the bubble form on a surface (no energy needed) is easier.
Peroxides are decomposed by metals and metal containing compounds (including many metal containing enzymes in the body. This is because the peroxide is energetic enough to join onto the metal atom and then break apart
Thanks - I was looking for a physical sort of answer like that. Thank you.
From the Wikipedia: “Catalase is a common enzyme found in nearly all living organisms. Its functions include catalyzing the decomposition of hydrogen peroxide to water and oxygen.[1] Catalase has one of the highest turnover rates of all enzymes; one molecule of catalase can convert millions of molecules of hydrogen peroxide to water and oxygen per second.[2]” Catalase - Wikipedia
I had an ear ache a couple weeks a go and my doctor suggested I pour a few drops of 3 % peroxide solution in my ear. The pharmacist even sold it in special dropper bottles for that purpose.
Hearing and feeling the peroxide bubble, fizz and go “pop!” and “crackle!” in my ear was the most funny cartoonlike silly experience I had in months. I sure can recommend it. 
Ahem… carry on.
To cause an ear ache, try this trick with 70% isopropyl (rubbing) alcohol! Painful AND pointless! Not exactly something to put on my resume.
Heh. One time when I was a student, the health service doctor flushed the wax out of my ears with a large syringe and plain water. He followed up with a drop of isopropyl alcohol, explaining that it got the water out, and that he had members of the swim team use it after practices to prevent ear infections. It probably has some value in that regard - it reduces the surface tension, and lets the water run out, but it stings like hell.
Why do peroxides and alcohols kill bacteria and viruses? (I’m aware that viruses are not truly alive.) I know peroxides are “unhappy” about having that extra oxygen, and I assume they shove it off onto the bacteria, but why does that kill it? Alcohol is a pretty stable molecule, and I don’t understand why it’s some sort of magic bullet for sanitation.
alcohol essentially dries out any bugs as it sucks the water out of them by osmotic pressure.
Hydrogen peroxide reacts with may sorts of chemicals or organic groups that might be in living system, oxidising them so they dont work
But viruses can’t be dehydrated, right? Does alcohol kill them?
I can only go so far with this, but pure oxygen is a poison. It’s a very dangerous material for animals. I imagine it is because of its tendency to engage in disruptive chemical reactions in the tissues, perhaps like the halogens. Out over my skis here.
It could potentially destroy the structure through a denaturing process (irreversible change in the protein structure surrounding the viral core). However, some viruses are resistant - from Yahoo answers
“Found this at Suite101.com:
It’s true that many viruses are readily inactivated by alcohol; but, some are not. Viruses consist of nucleic acid surrounded by a protein shell. Some viruses have an additional envelope. Generally, enveloped viruses are susceptible to alcohol: Herpes simplex virus (HSV), human immunodeficiency virus (HIV), influenza virus (Flu), respiratory syncytial virus (RSV), vaccinia virus, Hepatitis B and C viruses are considered susceptible to alcohols. However, there are certain non-enveloped viruses such as hepatitis A and enteroviruses, which are both responsible for viral gastrointestinal infections. Depending on the alcohol concentration of a hand-cleanser and time of exposure to the alcohol, hepatitis A and other non-enveloped viruses may not be eliminated.”
A fun (but kind of gross) science demo is to take some bulk blood (a liter or so from a butcher perhaps) and pour some peroxide into it. You get a giant bloody bubbling column. Fun times.
Huh? What in the world would this do for an ear ache?
I would guess it has more to do with the fact that the alcohol mixes with the water left in your ear and the resulting solution evaporates quicker than water alone.
From watching my wife do it, all hydrogen peroxide does is prolong it. Sure, the peroxide kills bacteria on the skin, once it’s done, it is now 100% pure water, making sure your ear canal is nice and moist, providing a perfect medium for the remaining bacteria to grow. I’ve finally convinced her to follow up her peroxide treatments with alcohol to dry out the skin so the bacteria doesn’t immediately grow back.
Maybe the doctor suggested a carbamide peroxide that would kill bacteria and loosen earwax but doesn’t leave a bacteria friendly environment.