science lesson: what do bleach and hydrogen peroxide have in common?

[quesarah]

I've been posting a bunch of science lessons over in nightxade's journal as checks the chemicals in her household cleaners for potentially hazardous materials. I'm going to repost them here, just 'cause it's science and I love talking about science.

What do bleach and hydrogen peroxide have in common?

Hydrogen peroxide and bleach are both bases, chemical compounds that tend to have high pH. There are "strong" bases and "weak" bases, and these characteristics are related to how easily they shed a part of their structure (called a hydroxyl group) that is very chemically reactive. Once it's been released into solution, the hydroxyl group will raise the pH and catalyze a number of different reactions called "oxidation" reactions. As you can imagine, how corrosive a base is directly relates to how strong the base is.

Bleach is a very strong base and tends to be sold in slightly more concentrated form. Hydrogen peroxide is a weak base and all commercially available solutions are relatively dilute. Both are hazardous, but there are levels of severity.

The same principle about bases also applies to acids, except they shed hydrogen ions instead of hydroxyls. Vinegar is an acid; a weak, dilute acid, but an acid nonetheless. We use a concentrated pure form (acetic acid) in the lab all the time and it's not to be handled carelessly. However, dilute it 50-fold and it's safe to consume.

/end science lesson

Comments

[khayman.livejournal.com]

~admits~ I really like reading these kind of posts. Good for the brainmeats. Better than most people's usual (myself included):

"So yeah, I went to the mall. And Tony was being such a dick today. And my mom was bugging me about cleaning my room. And I think I'll major in applied quantum theology. OMG this song is so great."

[biogeekgrrl.livejournal.com]

Thanks. The posts make slightly more sense in context of her initial posts but hopefully they're still informative on their own.

[distraction77.livejournal.com]

These are WAY fun!

I was brought up to use hydrogen peroxide not only on cuts and puncture wounds (ie. piercings), but also as mouthwash whenever I saw a little blood on the tooth brush. Mom told me that the little bubbles were fighting infection. Since then I have learned that my Mom was both literally insane and a drug addict, so I now question everything she ever told me. Thus.

What is the proper household way to use hydrogen peroxide?
(Was my Mom on crack and trying to kill me?)

[biogeekgrrl.livejournal.com]

Yay, people are having Fun with Science!

Okay, about Hydrogen peroxide. I too was brought up to use it on cuts and scrapes because it is a powerful disinfectant. The hydroxyl group is what does the work; it causes other compounds (like compounds in bacterial cell membranes and viruses) to undergo a process called oxidation. Sometimes oxidation is perfectly fine; the cells in your body harness energy in a series of back and forth chemical reactions called "oxidation-reduction" cycles. (Reduction is the reverse process of oxidation). The bad thing is, just one half of an oxidation-reduction cycle can cause tremendous damage to biological compounds. One example I always like to use is:

Iron + oxidating agent --> Iron oxide, aka rust

This is partly why there is concern in the medical field about people getting enough foods that have anti-oxidant properties, because they provide the other half of the oxidation-reduction process and keep everything in balance. Biological systems are very much about balancing.

So, to finish up the long answer to your short question, the proper household use of hydrogen peroxide is on surfaces you want to disinfect rather than on skin or wounds. And when you use it on surfaces, wipe it down with water afterwards just for good measure. For wounds, gargling and similar uses I recommend salt water. It does a perfectly good job of cleansing and disinfecting without the side effects of peroxide. In my neighborhood, I can go to Henry's or Whole Foods and purchase non-iodized table salt or sea salt in bulk. With that, I make the saline I use to clean my piercings, rinse my nose, gargle and so on.

One last thing, regarding the bubbles: hydrogen peroxide, when it's dissolved and not actually reacting with another chemical will decompose into H2O and O2, or water and oxygen gas. The bubbles are oxygen gas being released from the unreacted and now-inert hydrogen peroxide.

[kimberlychapman.livejournal.com]

It's weird to me because even though I academically understand that bleach is a base, instinctively anything that eats away at something else feels like it ought to be an acid. I instinctively think of acids as being like vinegar and bases as being like baking soda...the base being inert until exposed to the acid and then it all going FWOOM. :)

Your explanation is very cool and sensible, though!

[biogeekgrrl.livejournal.com]

I understand, I had much the same preconception going into Chem 101. But there I learned that there are some very active and corrosive bases. Sodium hydroxide, potassium hydroxide? Yow. They might come in solid form but they're very chemically reactive!

Glad you liked the description. :)

[woe2you.livejournal.com]

Woo! Brain candy. Cheers.

[biogeekgrrl.livejournal.com]

Rock on!