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Lye

    In ancient times, lye could be made  entirely with natural materials. Ancient peoples would burn wood at a very high temperature to create a white ash. 

    Today, lye is made through a reaction between sodium bicarbonate and calcium hydroxide. This combination produces sodium hydroxide. 

     Soap is the creation of the reaction between oils and lye (sodium hydroxide). Lye is a base while oils are considered acidic. Oils consist of ester bonds. Ester bonds have one carbon and two oxygen. One of the bonds between an oxygen and carbon is a double bond. This means that the carbon and one oxygen share electrons. Oxygen has a slight negative charge while carbon has a slight positive charge, but technically, the oxygen is dominant in the bond.  

    Before the oil and lye is mixed, the lye is mixed with water which creates 'lye water'. When the water and lye are mixed together, it produces heat causing the solution to become very hot.  This is because the bonds within the lye are being broken down by the water which is creating energy. There is no need for this extra energy. Therefore the product of this reaction is heat. The reaction is called exothermic because the energy is being given off.
     The next step is to mix the lye water with oils that have been heated. This is where saponification happens. Once the oils and lye water are added together, they must be mixed.

     The oils are referred to as triglycerides. Since lye water is a base, it breaks down the bonds in the oils, an acid, to create two molecules. The two molecules created are salt and glycerin. 

     The hydroxide, from the lye, which is slightly negatively charged attacks the double bond between the carbon and the oxygen within the triglyceride (oil). This then cause the oxygen to become fully negative because it takes two electrons from the carbon in which they were sharing between their double bond. The negatively charged oxygen ion expels an additional oxygen. So far, two bonds have been attacked. From here, the carbon holds on to the oxygen included within the hydroxide. This oxygen is of course slightly negative. The hydrogen is given off to the salt because the slightly positive hydrogen is attracted to the slightly negative oxygen within the salt.  Finally, the sodium, which is slightly positive, attaches to the negative oxygen. The saponification process is completed. 




   



Saponification is the process in

which the fats and oils react with the

lye water in order to create soap.

The fats and oils stabilize the pH of

the soap. The fats and oils are the acid 

while lye is a base. Through 

saponification they 

create a salt. 

Soap. 

Saponification

Chemistry 

How Soap Cleans

     Soap is of course used to cleanse ourselves. We use it everyday but never think to ask, "How does it work?" Well I will tell you!  

   Within soap there are different bonds as was discussed in the process of creating soap previously. There are soap molecules within our soap and these molecules are what make us clean. 

   Water is an immiscible liquid. This means that does not mix with oils. The role of the soap molecules are to emulsify the water and the oils in order for them to be rinsed away. 

    Soap molecules have a long  hydrocarbon chain with a carboxylate head. The head of the molecule is hydrophilic which means that it is water loving and oil fearing, while the tail of the molecule is hydrophobic and is the exact opposite. The tails of the molecules attract which creates a spherical cluster where the tails are within the cluster and the heads are out. These clusters are called micelles. The heads of the soap molecules are all negatively charged causing them to repel each other when in water.

   When the soapy water is applied to the dirty areas of our body, the tails break up the micelles that are apart of the oil. The tails trap the oil and dirt into another form of a micelle which can then be rinsed away. Now we are clean!

   

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