How Does Bleach Work

Kent - March 5, 2023

ELI5 : How Does Bleach Work?

Real ELI5

The colours of stuffs are determined by how their electrons arrange themselves. Bleach is an arsehole that rips away electrons from coloured stuffs, so the specific arrangement that gives stuff colour is mixed up and it won’t give out the same colour anymore.

More details:

To understand bleach we must understand chlorine, and to understand chlorine we must understand electron shells.

Keep in mind that the idea of an electron “shell” is an abstraction, but the general idea is that atoms are orbited by electrons, and those electrons live in various shells, or orbits, around the atom - a bit like a moon orbits a planet (only very tiny and physics gets very strange when things are very tiny).

What’s important here, though, is that these orbits can have a certain number of electrons each before they’re full and you have to move to the next orbit. And atoms want to fill those spots - an atom with a full outer-most electron shell is a happy stable atom, and atoms that aren’t full will try to fix that. A lot of the time, they fix that by joining up with other atoms, making molecules - water, for instance, is famously ‘H2O’: two hydrogen atoms (which have one electron in their outer shells each, and would kind of like to have two) and one oxygen atom (which has six electrons in its outer shell, and would really like to have eight). The hydrogens each share an electron with the oxygen and get one shared back in return, so everyone’s happy (the hydrogens pretend they have two, the oxygen pretends it has eight!). They’re friends now, and hang out together as a water molecule.

The closer an atom is to being “full” on electrons, the harder it’ll fight to complete the set. Oxygen’s pretty reactive because it only needs two electrons to be complete! So close. So close. It’ll bind with whoever can offer it a spare electron or two, so that it can be fulfilled. In honor of this ability, and oxygen being so commonly-studied, we call atoms or molecules with this property “oxidizers”.

Chlorine needs one. One, measly, piddling, little, electron. It will fight to get it. It will tear other molecules apart if it can turn what’s left into new (stable, or stable-ish) molecules that can complete it. It’s not the most powerful oxidizer, but it’s very mean, and that’s why you have to be careful with chlorine-based cleaners or - worse - chlorine gas (you, dear reader, are full of molecules that chlorine would love to take apart).

All of which takes us back to bleach. “Bleach” can technically be a few different chemicals, but most often it’s a chemical called sodium hypochlorite (diluted, probably in water). Sodium hypochlorite is a sodium atom, an oxygen atom, and a chlorine atom. It is safer to store than pure chlorine, but not very stable - if you let it, it will break down and free up the chlorine it has. The chlorine will be so very cold, so very alone now, and will go find organic molecules (like bacteria, or organic stains, or organic dyes in clothing) and tear them apart so that it can be happy. Bacteria dies, stains get broken apart, and the nice colorful dye molecules get broken down into something less colorful.

Other bleaches tend to work the same way, with different oxidizers or oxidizer-like processes.

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