Do you ever wondered why just a small piece of soap can make our bodies clean?  It's funny. We've been using soap since birth, yet most of us never even thought about this before now.

What is soap?

Soap is a salt of a fatty acid. There are many different types of fats such as animal fats and vegetable fats. Vegetable fats are usually liquid at room temperature whereas animal fats are usually solid at room temperature. Soaps are made of molecules that are both fat and water soluble. The molecule has a long hydrocarbon tail that allows it to dissolve grease, and a carboxylate polar head that is water soluble. The head is the sodium or potassium salt of an organic acid. Soaps are mainly used as surfactants for washing, bathing, and cleaning. 

How soap is made?

Soap is produced from the hydrolysis of fats in a chemical reaction called saponification. Saponification is a chemical reaction between a strong base and a acid, triglyceride (fat or oil) that results in the formation of a salt. There are two ways chemists can accomplish saponification. In both cases, they start with a material rich in triglyceride fats, like animal or vegetable oil. 

• One technique involves treating the fat with lye or another very powerful base to saponify it.

In this process, the triglyceride is reacted with a strong base such as sodium or potassium hydroxide to produce glycerol and fatty acid salts. Triglyceride is a compound made of three fatty acids, attached to a single molecule of glycerol. The salt of fatty acid is called soap. Fatty acids are straight-chain monocarboxylic acids. There are two types of fatty acids, saturated fatty acids and unsaturated fatty acids. The carbon-carbon bonds in saturated fatty acids are all single bonds, while unsaturated fatty acids have one or more carbon-carbon double bonds in their chains. Fatty acids are seldom found as free molecules in nature but are most often a part of a larger molecule called a triglyceride. Triglycerides consist of a three-membered carbon chain (glycerol backbone) with a fatty acid bonded to each of the three carbon atoms in the glycerol backbone. The bond between the fatty acid and the glycerol backbone is referred to as an ester linkage. In the saponification process the ester linkage is broken to form glycerol and soap. 

This process involves hydrolysis, where water molecules cleave into hydroxide anions and hydrogen cations, yielding glycerol and soap. The acid could be olive oil or coconut oil. Each acid has a unique combination of triglycerides which combines with the base (lye) differently. The base must always be composed of 1 hydroxide ion. Lye is always use as base because lye contains one sodium ion and one hydroxide ion. The equation of saponification is shown below:

 

• The other requires two steps, one to steam the fat  to speed up the reaction and another to treat it with alkali. 

When the mix is actually boiled (100 °C+), and after saponification has occurred, the "neat soap" is precipitated from the solution by adding common salt, and the excess liquid is drained off. This excess liquid carries away with it much of the impurities and color compounds in the fat, to leave a purer, whiter soap, and with practically all the glycerine removed. This process tends to result in a soap of purer quality, and the soap may also be less harsh on the skin.

How soap cleans?

Soap is an excellent cleanser because of its ability to act as an emulsifying agent. An emulsifier is capable of dispersing one liquid into another immiscible liquid. There are substances which can be dissolved in water, as for example the salt, and others which can't, as for example oil. Since oil doesn't mix with water, water cannot clean the oil, so soap is needed to suspend oil/dirt so that it can be removed during rinsing. The soap molecules work as a "bridge" between polar water molecules and non-polar oil molecules. Soap molecules have both properties of non-polar and polar at opposite ends of the molecule.

Soap is formed by molecules with a "head" which likes water (hydrophilic) and a long "tail" that hates water (hydrophobic). The head of a soap is a negatively-charged, polar molecule. Its hydrophilic (water-loving) carboxylate group (-CO₂) interacts with water molecules via ion-dipole interactions and hydrogen bonding. The hydrophobic (water-fearing) part of a soap molecule, its long, nonpolar hydrocarbon chain, does not interact with water molecules. The hydrocarbon chains are attracted to each other by dispersion forces and cluster together, forming structures called micelles. In these micelles, the carboxylate groups form a negatively-charged spherical surface, with the hydrocarbon chains inside the sphere. Because they are negatively charged, soap micelles repel each other and remain dispersed in water.

Then when soap is added to the water, the long hydrophobic chains of its molecules join the oil particles, while the hydrophilic heads go into the water. The nonpolar hydrocarbon portion of the micelles break up the nonpolar oil molecules. A different type of micelle then forms, with nonpolar soiling molecules in the center. Thus, grease and oil and the 'dirt' attached to them are caught inside the micelle and an emulsion of oil in water is then formed, As a result, the oil droplets repel each other and remain suspended in solution With the rinsing, the emulsion is taken away.

Soaps are also surfactants ("surface active" substances) and as such perform other important functions in cleaning, such as loosening, emulsifying (dispersing in water) and holding soil in suspension until it can be rinsed away. Surfactants can also provide alkalinity, which is useful in removing acidic soils. 

Surfactants are classified by their ionic (electrical charge) properties in water: anionic (negative charge), nonionic (no charge), cationic (positive charge) and amphoteric (either positive or negative charge).

Soap is an anionic surfactant. Water, although a good general solvent, is unfortunately also a substance with a very high surface tension. In the body of the water, each molecule is surrounded and attracted by other water molecules. A tension is created as the water molecules at the surface are pulled into the body of the water. Because of this, water molecules generally prefer to stay together rather than to wet other surfaces and inhibits the cleaning process. Surfactants work by reducing the surface tension of water, allowing the water molecules to better wet the surface and thus increase water's ability to dissolve dirty, oily stains.

Why soap is not effective?

Although soaps are excellent cleansers, they do have disadvantages. They are not effective in hard water. Hardness in water is caused by the presence of mineral salts - mostly those of calcium (Ca) and magnesium (Mg), but sometimes also iron (Fe) and manganese (Mn). The mineral salts react with soap to form an insoluble precipitate known as soap film or scum. The scum cannot rinse away easily. It tends to remain behind and produces visible deposits on clothing and makes fabrics feel stiff. It also attaches to the insides of bathtubs, sinks and washing machines. This reduces the amount of soap available for cleaning

2 CH₃(CH₂)₁₆CO₂^-Na⁺ + Mg²⁺ → [CH₃(CH₂)₁₆CO₂^-]₂Mg²⁺ + 2 Na⁺

They are also not effective in weak acid. As salts of weak acids, they are converted by mineral acids into free fatty acids. These fatty acids are less soluble than the sodium or potassium salts and form a precipitate or soap scum. Because of this, soaps are ineffective in acidic water. Also, soaps form insoluble salts in hard water, such as water containing magnesium, calcium, or iron. To achieve the same washing or cleaning action, more soap must be added.

CH₃(CH₂)₁₆CO₂^-Na⁺ + HCl → CH₃(CH₂)₁₆CO₂H + Na⁺ + Cl^-

 Can you believe that these are actually MADE OF SOAP?

So real right? ;)

Oh My God, Chemistry test tomorrow!
Oh My God, Why is it Chemistry so difficult?

Oh My God, Why should I study Chemistry?

Oh My God......!!!

Does above lines familiar to you?

Chemistry especially Organic Chemistry has a reputation among the science students as being a difficult subject to master. 

Organic chemistry is the study of the structure, properties, and reactions of compounds that contain carbon. Since not all carbon reactions are organic, another way to look at organic chemistry would be to consider it the study of molecules containing the carbon-hydrogen (C-H) bond and their reactions. Organic chemistry is important because it is the study of life and all of the chemical reactions related to life.

It is hard because you need a lot of memorization of different types of compounds and you have to pull together a lot of chemical concepts and applying them together. However, consistent hard work of memorizing, practicing and revising will eventually let organic chemistry sounds easier to you. Just remember, never give up!