Cleansing Agent Soaps- Definition, Properties, Soap Making Process, Mechanism of Cleansing Action, Practice Problem, FAQ

You must have listened to these words from your teacher, “Wash your hands frequently for at least 20 seconds with soap and water”. Some of you might wonder how these foams come in soap when we rub our hands? Soaps now become an essential part of our life. When we wash our hands with soap, the germs on our hands are removed. This keeps harmful germs out of our bodies and keeps us healthy. Handwashing with soap can help prevent a variety of infections, from the common cold to potentially fatal illnesses like pneumonia and influenza. It can also save lives: research suggests that clean birth practices like handwashing with soap can increase the survival percentage of newborns by 44 %.

You must have seen some yellow spots on your washroom tile, floor or near the kitchen sink. These are soap scum which can be found on shower curtains, bathroom fixtures, bathtubs, shower doors, tiling, and more. There is a variety of uses and functions which we must know about soaps, so let’s begin to learn some interesting facts about soap and its cleansing properties.

Table of content:

• What is soap?
• Properties of soap
• Soap making process
• Mechanism of cleansing action of soap
• Types of soaps
• Action of soaps on hard water
• Practice problems
• Frequently asked questions-FAQ

What is soap?

• Soap is a fatty acid salt described in chemistry. 
• Soaps are mostly employed as surfactants in washing, bathing, and cleaning, but they are also key components of lubricants and are used in textile spinning. 
• Soaps are fatty acid sodium or potassium salts that are water-soluble. Soaps are created by chemically processing fats and oils, or their fatty acids, with a strong alkali. 
• Soap is essential for good hand washing and hygiene, although in emergency cases, clean ash or sand/soil can be used as a substitute, as advised by the World Health Organization.

Properties of soap: 

• Cleansing: The primary reason most individuals use soap is to clean themselves. A soap molecule is made up of a carbon chain, with one end attracting oil and the other attracting water. Therefore, the cleansing ingredient should be balanced in the soap, with neither too much nor too little of it being added during manufacturing.
• Conditioner: Emollients are the chemical compounds found in soap conditioners. The amount of soap left on your skin when you've just washed your hands and rinsed them depends on what type of soap you use.
• Hardness- Harder soap, in the form of a dense bar which lasts for longer.
• Soap acts with mineral salts to generate soap film, which is an insoluble precipitate.
• The fragrance is an important component. Aromas elicit a distinct mix of personal memories and enrich our daily lives. Fragrances invigorate, relax, and, most importantly, hide our bodily odours.

Soap-making process:

• Over the years, the process of producing soap has remained unaltered. 
• Rainwater, potash, and animal tallow were mixed together in ancient Roman tradition. It took considerable time and effort to make soap. The fat had to be rendered first (melted and filtered).
• Potash solution was then added. Because water and oil do not mix, this combination needed to be swirled constantly and heated to keep the fat melted. Slowly, a chemical reaction known as saponification occurred. The triglyceride fats involved in this process are hydrolyzed into free fatty acids, which subsequently react with the alkali to create crude oil.
• Soap is a mixture of soap salts, excess fat or alkali, water, and glycerol that has been liberated (glycerin). Glycerin is a beneficial by-product that can be left in the soap as a finishing touch and can be separated for other purposes or as a softening agent.

Let us study this saponification reaction in brief

Saponification reaction:

The cleansing action of soap:

Consider the case of soap solutions. Soap is a sodium or potassium salt of a higher fatty acid that can be written as RCOO^-Na⁺ (for example, sodium stearate CH₃(CH₂)₁₆COO^-Na⁺ , which is a common ingredient in bar soaps). It dissociates into RCOO-and Na+ ions when dissolved in water. The RCOO^- ions, on the other hand, are made up of two parts: a hydrophobic (water-repelling) long hydrocarbon chain R (also known as non-polar 'tail') and a hydrophilic polar group RCOO^- (also known as polar-ionic 'head') (water-loving).

A micelle is made up of a hydrophobic hydrocarbon–like central core. The cleansing action of soap is due to soap molecules forming micelles around the oil droplet in such a way that the hydrophobic part of the stearate ions is in the oil droplet and the hydrophilic part of the stearate ions extends out of the grease droplet like bristles. The oil droplet surrounded by stearate ions is now sucked in water and removed from the filthy surface because the polar groups can interact with water. Soap aids in the emulsification and removal of oils and fats. The globules' negatively charged coating prevents them from clumping together and creating aggregates.

Types of soap:

Almost all soaps are created by heating fats or oils with soluble hydroxide. Different raw materials are used to create variations.

• Toilet soaps are made with higher-quality fats and oils, with extra care given to remove superfluous alkali. To make these more appealing, colour and scents are added.
  • Transparent soaps: Floating or transparent soaps are created by pounding tiny air bubbles before they harden. To make transparent soap, dissolve the soap in ethanol and then evaporate the excess solvent.

• Medicated soaps: Medicated soaps contain ingredients with medical benefits. Deodorants are included in certain soaps to make you feel fresh and hygenic.

• Shaving soaps: Glycerol is used in shaving soaps to avoid quick drying. When producing them, rosin is used as a gum. It produces sodium rosinate, which has a good lather.

• Laundry soaps: Fillers in laundry soaps include sodium rosinate, sodium silicate, borax, and sodium carbonate.

Soap chips are formed by scraping little broken pieces of melted soap from a thin sheet onto a cool cylinder. Soap grains are microscopic soap bubbles that have been dried. Soap powders and scouring soaps contain soap, an abrasive (powdered pumice or finely divided sand), and builders such as sodium carbonate and trisodium phosphate. These builders help soap for better cleansing actions.

Action of soaps on hard water

• The amount of dissolved calcium and magnesium in the water is the simplest definition of water hardness. In hard water, soap reacts with the minerals such as calcium and magnesium salts to form "soap scum".
• Calcium and magnesium ions are found in hard water. When sodium or potassium soaps are dissolved in hard water, these ions generate insoluble calcium and magnesium soaps, respectively.

• In water, these insoluble soaps separate as scum and are ineffective as a cleansing agent. In reality, because the precipitate sticks to the fibre of the cloth as a sticky mass, this is a hindrance to good washing. Because of the sticky precipitate, hair rinsed with harsh water appears drab. Because of the sticky mass, the dye does not absorb uniformly on cloth cleaned with soap in hard water.

Practice problems: 

Q1. Handmade soaps are manufactured using

A. Cold process
B. Hot process
C. Laboratorical process
D. Fully boiled process

Answer: A

Solution: Handmade soaps are manufactured using cold process

Q2.Critical micelle concentration is_____________________.

A. the concentration below which micelle formation takes place.
B. the concentration above which micelle formation takes place.
C. the concentration at which micelle formation takes place.
D. the concentration at which the surface became unsaturated.

Answer: B

Solution: Critical micelle concentration is defined as the concentration above which micelle formation takes place. The surface becomes saturated at the CMC point, and adding more surfactant molecules has no effect on the surface tension.

Q3. Soft soaps are restricted to hot processes because of their _____________

A. Low alkaline nature
B. High alkaline nature
C. High solubility in oil
D. High solubility in water

Answer: D

Solution: Because of their higher water solubility, soft soaps restrict to hot process constraints. The cold procedure produces a soft soap when potassium hydroxide (KOH) is utilised. It will not work in harsh water.

Q4.The pH of the soap solution lies between the range of
A. 6-7
B. 5-8
C. 9-10
D. 4-5

Answer: C

Solution: The pH of the majority of the soaps is between 9 and 10.

Frequently asked questions-FAQ

Q1. Who invented the versatile substance “soap”?

Solution: In 2800 B.C., the Babylonians were the first to invent soap. They discovered that combining fats, specifically animal fats, with wood ash generated a cleaner product. The first soap was used to wash textile industry wool.

Q2.What should I do if I accidentally get soap in my eyes?

Solution: If you accidentally get some soap cleanser in your eye and it hurts, rinse it out with cool, clean water right away. Allow running water to flow over your eyelid while holding it open.

Q3. Are soaps good for washing hair?
Solution: Using soap on your hair can do considerable damage, leaving it dry, harsh, and brittle. Lack of conditioning agents and soap scum are mainly responsible for your hair damage.

Q4.What if a child consumes soap?
Solution: Soap has low toxicity. Give your child a few sips of water and wait for vomiting and loose stools if they ate soap.

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