Cleansing Action of Soap and Detergents

Cleaning with only water does not work effectively, as the surface tension is too high for cohesive forces to work.

Cleaning agents are compounds that are used to remove stains, dust, unpleasant odors, dirt, and other contaminants from surfaces. These are the chemicals that are used to reduce surface tension on planes so that water can do its role effectively.

Soaps have a molecular structure made up of lengthy chains of molecules. The hydrophobic end (the tail) of the hydrocarbon chain is on one end. These molecules repulsed water and clung to the oils and grease. The water-loving, or hydrophilic, chain, made up of anionic molecules, is then at the top of the chain. Soaps and detergents are two very common cleaning agents in our daily life.

Soaps

In a saponification reaction, sodium hydroxide or potassium hydroxide reacts with vegetable or animal fats to produce soap. Soaps are salts made up of a long chain of potassium or sodium-based fatty acids. Soaps are water-soluble by their very nature. When an ester combines with a base, resulting in the creation of alcohol and soap, this is known as saponification. The reaction of universal saponification is shown below.

Ester + Base Alcohol + Soap

Detergent

Any synthetic chemical that cleans well and can be employed as a surface-active agent in both hard and soft water is referred to as a synthetic detergent. It’s a non-soap cleanser that works by lowering an aqueous cleaning agent’s surface tension.

Another type of cleaning agent is synthetic detergents. These are just like soaps in that they have all of the same properties. They don’t contain any soap, and their chemical makeup is quite different from that of soaps.

Synthetic detergents are also known as alkyl hydrogen sulfates of long-chain alcohols or alkyl benzene sulphonates. Soaps and synthetic detergents both harm water since they aren’t totally biodegradable.

Cleansing Action of Soap

The dirt is usually oily in nature and water-insoluble. The dirt is washed away by the soap’s micelle production process. Before we get into the details of soap’s cleansing effect, it’s important to first understand what a micelle is.

What is micelle?

The cluster of molecules that make up a micelle are arranged in a spherical shape with the hydrophobic end facing inside and the hydrophilic end facing outwards.

In water, soap molecules form micelles and conduct the following cleansing actions: – Because soap has both a hydrophobic and a hydrophilic end when it is dissolved in water, the hydrophilic end is pulled to the water and faces outwards, while the hydrophobic tail is drawn to the water and faces inwards. The hydrophobic end of soap molecules is facing away from water, whereas the hydrophilic end is facing towards water, as shown in the image below.

Now, these molecules begin to clump together around the dirt molecule, with the hydrophilic head facing outwards and the hydrophobic tail facing inwards, away from the water, forming a micelle. The image below depicts the production of micelles by soap molecules.

Because the dirt is now trapped within the micelle, the soap molecule in the form of micelles can clean it. Micelles developed in the water to form a colloidal solution. When the cloth or surface is washed with soap and water, the hydrophilic end is attracted to the water, and the dirt molecule trapped inside the micelle is rinsed away.

Cleansing Action of Soap and Detergents

The cleansing action of soaps and detergents is due to their capacity to reduce the surface tension of water, emulsify oil or grease, and retain it in suspension in water. Soaps and detergents have this potential due to their structure. A sodium soap dissolves in water to produce soap anions and sodium cations. The ionisation of sodium palmitate, for example, is depicted in the chemical equation below.

A soap anion is a long hydrocarbon chain with a carboxylate group attached to one end. In oils or grease, the hydrocarbon chain, which is hydrophobic, is soluble. The carboxylate group, which is hydrophilic and soluble in water, is the ionic component.

A detergent dissolves in water to produce detergent anions and sodium cations. The ionisation of sodium alkyl sulphate and sodium alkylbenzene sulphonate, for example, is seen in the chemical equations below.

Similarly, the anion element of a detergent has a hydrophobic and a hydrophilic component.

The following describes how soap or detergent removes a grease stain from a piece of cloth.

A soap or detergent anion is made up of two parts: one that is hydrophobic and the other that is hydrophilic.

Because soap or detergent lowers the surface tension of water, the cloth’s surface gets fully wetted. In grease, the hydrophobic components of soap or detergent anions dissolve. The hydrophilic portions of anions are water-soluble. 

The droplets are suspended in water due to repulsion between them, forming an emulsion. As a result, the droplets do not congeal and do not reappear on the cloth. The droplets are washed away by rinsing.

Conclusion:

Cleaning agents are substances that are applied to surfaces to remove stains, dust, odours, dirt, and other impurities. Sodium hydroxide or potassium hydroxide interacts with vegetable or animal fats to generate soap in a saponification reaction. Soaps are salts made up of a lengthy chain of fatty acids derived from potassium or sodium.