Source of pictures: pixabay.com
It is a good day for playing football in a sunny Sunday.MackleandLindawereplayingfootballoutdoors. "Mackle, dinner isready!", ashe heardmother's voice, hestopped playing and said goodbye toLinda.Then herushed upstairsfordinner.
"Takeoffyourshoes.Yoursocks arestink," pointingat his trainers,Momstood at the door with another hand on her hip.
"OK," hereplied. "And you have to learn to wash your socks. Ican't do it for you forever," mother continued.
"No problem,"he answered quickly.However,heactually mumbled to express his dissatisfaction.
After thedinner,hewent to washthesocks witha basinandabarof soap. The sweat and stainswere dissolved by the water insuds. Hefelt doubtful:were theyreallywashedcleanly? Whenthe socks were drythe next day,theybecame white and clean again. Why did socks get clean again? Why can soapwash clothes cleanly?
We can't see what happensto clothes when they arerubbedagainst each otherin thesuds.In fact, there are magical principles. The ingredient of the soap we usuallyuseis "advanced sodium Aliphatate". This ingredient makes the soap used as a "surfactant". The microstructure of the surfactantisgenerallycomposed oftwo parts. One endprefers to getclose to water, so we call it a "hydrophilic group".The other end gets far away from waterwhile itlikesoil, so we call ita "hydrophobic group" or "lipophilic group".Advanced sodium Aliphatate isthe same as what we just saidand itsmolecule iscomposed of two parts. The end with the chemical "carboxyl"favors waterand is a "hydrophilic group"; the other part with "alkyl"isn’t a fan ofwaterbutlikesoil and is hydrophobic group.
When the moleculeofthe soap is in water, its hydrophilic group,i.e. the end with the carboxyl, is more willing to stick to the water molecule.However, the hydrophobicend withthealkylwill stay away from the water andbelikely to be combinedwiththeoilmolecule.Youcanimagine the oil molecule as a ball ofwool witha lot of needlesonit. The partof needles exposed out of the wool ball is the hydrophilicgroup. Asthis part likes water, it is exposed to the outside with water.Thepart inside the wool ball is the hydrophobicgroup.This part doesn't likewater, soit hidesinside the wool ball.
If this oily "wool ball" has a lot of needles on it, i.e.there are enough soap molecules, it will be surrounded by these molecules.By means of rubbing and washing with water, theoily ballor stains will break away fromitsoriginal attachment, disperse into smaller droplets, and then flow away with water. This is the principle for cleaning clothes and socks with the soap.Althoughother washing powders, soaps, etc.have various ingredients,they havethe sameprinciple.
Why notwash your socksbyyourself tonight?Imaginewhat’s happeningin the water.
Author: Ya Wen
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