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Author Topic: Bleach turns EVERYTHING white. Why?  (Read 8787 times)

Offline CurLz

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Bleach turns EVERYTHING white. Why?
« on: 13/01/2010 21:22:16 »
I spilled some bleach on my BRAND NEW jeans this morning (whilst doing the dishes).
It got me to thinking...Why does bleach turn everything white? What kind of chemical reaction is happening there?

Anyone know?


 

Offline rosy

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Bleach turns EVERYTHING white. Why?
« Reply #1 on: 13/01/2010 22:29:56 »
Bleach is an oxidising agent (well, at any rate, bleaches are oxidising agents). This means that they react in certain ways with certain groups of chemicals. For one thing, dyes are very often coloured by molecules with long chains of alternating "double" and "single" chemical bonds (most often between pairs of carbon atoms, but sometimes with a nitrogen or oxygen thrown in, these absorb some frequencies of visible light (depending on the chain) but not others, giving the light reflected from/shining through the dye a colour. The classic schoolbook example is carotene: http://en.wikipedia.org/wiki/Carotene See the section "the multiple forms" which shows the most informative molecular diagram in this case.
The oxidising agent breaks these bonds, disrupting the molecular chain, and the colour absorbing properties are lost.

Not everything is turned white by bleach, though. Oxidising some metals/metal ions (such as the iron in its Fe(II) form in blood to Fe(III) in the form, more or less, rust) merely changes their colour, Which is why you should never attempt to bleach a bloodstain.
 

Offline CurLz

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Bleach turns EVERYTHING white. Why?
« Reply #2 on: 16/01/2010 01:56:44 »
This is great guys. Thanks!
...very informative.
 

The Naked Scientists Forum

Bleach turns EVERYTHING white. Why?
« Reply #2 on: 16/01/2010 01:56:44 »

 

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