How does oil & dirt get washed away with soap?

Article Title: How does oil & dirt get washed away with soap?

Author: Dr. George Grant

Contact Author: mailto:chemicool1@yahoo.com

Web Address: http://www.internet-tips.net



We use soap each day in our lives in the form of detergents,

shampoo, shower crème, hand soap or bar soap. We are so used to

using soap that we rarely stop and wonder how this wonderful

compound manages to help us clean ourselves day after day. Have

you ever thought about what would happen if there were no soap? How

else can we rid the dirt off our bodies or our clothes?



Most of the time, dirt comes in the form of grease or oil which

sticks itself onto surfaces and will not come off if only water is

just used. This is because oil and grease are non-polar, which means

that the oil molecules are not charged and therefore are not

attracted to polar substances such as water. Because of this, oil

tends to stick with its own molecules or other non-polar substances.



On the other hand, water is a polar substance which is made up of

one positive and one negative charge, and therefore is a fragmented

substance. With this, water dissolves salt easily because salt is

made up of charged ions in which the positive charge will be

attracted to the negative ions in water.



Due to the fact of the nature of oil and water, you will see that

oil will not dissolve in water but remain clustered on the surface.

Also, oil and grease will stick onto plates and cutlery during

cleaning, and no amount of water can completely remove it. That's

when soap comes in. All it takes is just one layer of soap with

water and the oil will be removed. How does this happen?



Well, soap is a unique substance of potassium fatty acid salts,

produced through a chemical reaction called saponification. Its

molecules are made up of a hydrocarbon chain, which is non-polar, as

well as a carboxylate molecule which is polar. Therefore, the non- polar part of the soap – the hydrocarbon chain, is not attracted to water but to oil (lipophilic). On the other hand, the carboxylate

molecules which are negatively charged, are attracted to the

positively charged water molecules hydrophilic).



In this case, when soap is applied to oil and grease, the lipophilic

parts of soap will attach itself to the non polar molecules of oil.

However, the other component of soap, the hydrophilic component,

will be left on the surface. When water is applied onto this surface

with a sponge, the hydrophilic component will be attracted to the

water molecules and is lifted from the surface, together with the

oil. This way, both oil and soap is removed with the wipe of the

sponge. At the same time, because soap molecules have been combined

with oil, other soap molecules will also be attracted to it. This is

why you can see clusters of oil that are surrounded by soap within

the water that has been used for washing. Of course, once soap has

been used up to attract the oil, more soap would need to be added to

work on the access oil.In conclusion, our lives have been made

cleaner and easier through the wonders of a simple substance called

soap. Without it, we would be having a difficult time removing dirt,

oil and grease in our everyday cleaning.



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Author's bio:

Dr. George Grant is an experienced researcher in Bio-chemistry. He

has done extensive researches and experiments in the field. He is a

visiting faculty for some of the most reputed Science colleges.

http://www.chemicool.com