Soaps and Detergents - Preparation, Difference, Examples, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:48 PM IST

Soaps and detergents are used everywhere in our daily lives for ourselves, our homes, and our environment to be clean and hygienic. From waking up from bed to going to bed, we use these chemical compounds one way or another—starting from washing our hands with soaps to washing our clothes using detergents. Whereas they are ubiquitous in our daily lives, many among us take for granted the science behind cleaning agents and their impacts on our lives. The paper will present the soaps and detergents, their constitution, properties, and how they are applied in everyday life.

This Story also Contains

Understanding Soaps and Detergents
Types and Features
Synthetic Detergents
Applications in Real Life and Consequences
Some Solved Examples
Conclusion

Soaps and Detergents - Preparation, Difference, Examples, FAQs

Probably the most interesting thing about soaps and detergents is their ability to adapt to various situations or environments. On the mild extreme are balanced-pH formulae in baby shampoos, while on the opposite extreme are heavy-duty grease-cutting detergents used industrially—so cleaning agents are formulated to suit their users' needs. In personal care, soaps and detergents will become very instrumental in maintaining hygiene and containment from various diseases. Probably one of the most practical measures to help prevent the spread of infectious diseases is washing one's hands as frequently as possible with soap and clean water—something the COVID-19 pandemic made very clear.

Understanding Soaps and Detergents

Soaps and detergents are amphipathic molecules, meaning they have both hydrophilic and hydrophobic regions of the molecule. This unique characteristic gives them the capability of cleaning surfaces as well as lifting grease and dirt. Soaps are obtained by the reaction of fatty acids with an alkali metal; detergents on the other hand are tailor-made synthetic chemical compounds that mimic the soaps' cleaning action. They may or may not contain a soapy element.

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Sodium or potassium salts of higher fatty acids such as lauric acid(C₁₁H₂₃COOH), palmitic acid(C₁₅H₃₁COOH), etc. are called soaps. Sodium salts of fatty acids are known as hard soaps and potassium salts of fatty acids are soft soaps. Shaving creams and liquid soaps are soft whereas others are hard. Soaps are generally obtained by the hydrolysis of oils and fats with aqueous alkali. The process is called the saponification of oils and fats. Fats and oils are triesters of higher acids and glycerol. Hard soaps are prepared from cheap oils fats and sodium hydroxide. They contain free alkali and are used for washing purposes. Soft soaps are prepared from good oils and potassium hydroxide. They do not contain free alkalis and are used as toilet soaps, shaving creams, and shampoos. Transparent soaps are prepared by dissolving the soap in ethanol and then evaporating the excess solvent. Medicated soaps are soft soaps and are prepared by adding some antiseptics like Dettol, salons, etc. In some soaps, deodorants are added. Toilet soaps are prepared by using better grades of fats and oils and care is taken to remove the excess alkali. Colors and perfumes are added to make them attractive. Shaving soaps contain glycerol to prevent rapid drying. A gum called rosin is added while preparing these soaps. It forms sodium rosinate which leathers well. Laundry soaps contain fillers like sodium resonate, sodium silicate, borax, and sodium carbonate.

Why do soaps not work in hard water?

Hard water contains calcium and magnesium ions. These ions form insoluble calcium and magnesium soaps respectively when sodium or potassium soaps are dissolved in hard water.

$2 C_{17} H_{35} COONa + {CaCl}_{2} \to 2 NaCl + {(C_{17} H_{35} COO)}_{2} Ca$
Soap Insoluble calcium stearate(Soap)

These insoluble soaps separate as scum in water and are useless as a cleansing agent. In fact, these are hindrances to good washing because the precipitate adheres onto the fibre of the cloth as a gummy mass. Hair washed with hard water looks dull because of this sticky precipitate. Dye does not absorb evenly on cloth washed with soap using hard water, because of this gummy mass.

Types and Features

Soaps and detergents can also be classified into several classes based on their chemical makeup and properties. Anionic detergents, like sodium lauryl sulfate, exhibit good cleaning ability and find use in laundry detergents and shampoos. The cationic detergents find major use mostly as fabric softeners and disinfectants. Non-ionic detergents do not contain charged heads and find main application in dishwashing liquids and personal care products.

Synthetic Detergents

Clearly, synthetic detergents are an advance in cleaning. Some of them are very strong substitutes for traditional soaps. Synthetic detergents are chemical compound designed to work like a soap but will overcome some of the shortcomings of the latter, especially in hard water. They have equal cleaning action for household purposes, just the same as for industrial cleaning, because, unlike soap that forms insoluble compounds with hard water minerals, they do not lose their washing power.

The paper shall be on composition, types, and real-life applications that make synthetic detergents important for a myriad of purposes. We will start with an overview of synthetic detergents—what they are chemically and how they are different from soaps. Thereafter, we shall start classifying the various kinds of synthetic detergents by type, showing their various properties and applications. The last section makes some inferences about the usages of these synthetic detergents in relation to everyday life: their use in washing clothes and dishwasher use, and quantification of associated environmental impact in view of an increasingly sustainable compound formulation trend. By the end of this paper, the reader shall have clarity on what these synthetic detergents are and what their critical roles in modern cleaning practices have become.

These are also called synthetic detergents syndets soapless soaps or just detergents. They have cleansing power as good or better than ordinary soaps can be used for washing even with hard water and do not precipitate in the presence of ${Ca}^{2 +} / {Mg}^{2 +}$ or in acidic solution.
A synthetic detergent is the sodium salt of a long-chain alkyl hydrogen sulfate or the sodium salt of a long-chain benzene sulphonic acid. Like soap, they contain both hydrophilic and hydrophobic parts in the molecule.

Detergents are mainly classified into three categories, namely:

1. Anionic Detergents:

Anionic detergents are sodium salts of sulfonated long-chain alcohols or hydrocarbons. Alkyl hydrogen sulfates formed by treating long-chain alcohols with concentrated sulphuric acid are neutralized with alkali to form anionic detergents. Similarly, alkyl benzene sulphonates are obtained by neutralizing alkyl benzene sulphonic acids with alkali.

In anionic detergents, the anionic part of the molecule is involved in the cleansing action. Sodium salts of alkyl benzene sulphonates are an important class of anionic detergents. They are mostly used for household work. Anionic detergents are also used in toothpaste.

2. Cationic detergents:

These are mostly acetates, chlorides, or bromides of quaternary ammonium salts containing one or more long-chain alkyl groups. Being more expensive than the anionic detergents, they find limited use. But these detergents are also used in hair shampoos and hair conditioners. Such detergents, however, possess germicidal properties and are used quite extensively as germicides. Examples are trimethyl stearyl ammonium bromide, cetyl trimethyl ammonium bromide, or N-benzyl quaternary ammonium chlorides.

3. Non-ionic detergents:

They are neutral surface active detergents obtained from long-chain alcohols by treatment with ethylene oxide in the presence of a base. One such detergent is formed when stearic acid reacts with polyethyleneglycol. ${CH}_{3} {({CH}_{2})}_{16} COOH + HO {({CH}_{2} {CH}_{2} O)}_{2} {CH}_{2} {CH}_{2} OH \overset{- H_{2} O}{\to} {CH}_{3} {({CH}_{2})}_{16} COO {({CH}_{2} {CH}_{2} O)}_{3} {CH}_{2} {CH}_{2} OH$

NCERT Chemistry Notes:

Applications in Real Life and Consequences

Soaps and detergents are in great demand for individual hygiene, disinfection, and cleaning of a person's surroundings. One of the most benevolent practices to arrest infectious diseases like COVID-19 is handwashing, which can be performed with soap and water. Dishwashing liquids will keep the dishes free from food remains and bacteria, and laundry detergents remove stains and odors from clothes.

Extensive application of the soaps and detergents, however, opened an avenue of concern about the effect of the products on the environment. Phosphates are primary components of most traditional detergents and often enhance the eutrophication of the water bodies, resulting in a situation whereby oxygen is greatly reduced, killing the aquatic life. In response to such concerns, eco-friendly and biodegradable alternatives have been invented that include plant-based detergents and soaps manufactured from natural ingredients.

The study of soaps and detergents forms part of the academic curriculum designed to introduce a student to the principles of chemistry, especially the divisions of organic and surface chemistry. This includes the chemical reactions in the preparation of soaps and detergents and various factors that would have an effect on their cleaning effectiveness like pH, water hardness, and temperature.

Some Solved Examples

Example 1

Question: Which one of the following cannot be used as soap?

1. Stearic acid
2. Oleic acid
3. Palmitic acid
4. Bithional

Solution: Bithional acts as an antiseptic and is not used as soap. Stearic acid, Oleic acid, and Palmitic acid can be used as soaps. Hence, the answer is option 4.

Example 2

Question: Which of the following is used in the reaction called saponification?

1. Strong base
2. Strong acid
3. Hydrogen
4. Nickel

Solution: In the saponification reaction, fat or oil reacts with a strong base (NaOH) to produce soap molecules. Hence, the answer is option 1.

Example 3

Question: Soft soaps are the limitation of the hot process because of their

1. High alkalinity
2. Low alkalinity
3. Low solubility in water
4. High solubility in water

Solution: Soft soaps are more soluble in water, which is a limitation of the hot process. Hence, the answer is option 4.

Example 4

Question: Which one of the following is true about floating soaps?

1. These are made by beating tiny air bubbles before their hardening
2. These are made by dissolving soap in ethanol, then evaporating excess solvent
3. These are made by adding substances of medicinal value like Dettol, etc.
4. The soaps contain glycerol and rosin forming sodium resonate for lather

Solution: Floating soaps are made by beating tiny air bubbles into the soap before it hardens. Hence, the answer is option 1.

Example 5

Question: Transparent soaps are made by dissolving soap in which of the following solvents?

1. Methanol
2. Acetone
3. DMSO
4. Ethanol

Solution: Transparent soaps are made by dissolving the soap in ethanol and then evaporating the excess solvent. Hence, the answer is option 4.

Conclusion

Soaps and detergents have, therefore, become very essential commodities in our everyday life, keeping us clean, and hygienic, and ensuring good health. As we continue to use these chemical compounds, it becomes very necessary to also take into consideration the effects they are having on the environment and try to find more environmentally friendly ways. We learn the science of soaps and detergents to make conscious decisions and help in cleaning and healthy living.

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Frequently Asked Questions (FAQs)

1. What is the chemistry of soap action ?

Soaps are surfactants,they can dissolve in both water and oils.This Property of soap helps to remove oil and dirts. Soap is made by reacting fats/oils with a solid hydroxide base to produce glycerin and soap (fatty acid salts). Triglycerides are fat/oil molecules made up of glycerin chemically linked to three fatty acids.

2. .What is the nature of soaps and detergents?

Soaps are sodium or potassium-based fatty acid salts that are water soluble. Soaps are manufactured by chemically processing fats and oils, or their fatty acids, with a heavy alkali. As a result, they have very simple features and can be classified as simple salts

3. What are the differences between soap and detergent?

Soaps are the sodium salts of carboxylic acids having long chains. Soaps are biodegradable, however other detergents are not.The cleansing action of soaps and detergents are slightly different Soaps have a modest cleaning impact, but detergents have a powerful cleaning activity.

4. What are the properties of soaps?

Soaps are fatty acid sodium salts that are water soluble. Soaps are manufactured from fats and oils, or fatty acids, and are handled with solid alkali (a base). Fats and oils are the most commonly utilized procedure for manufacturing soap.

5. What is the chemical reaction involved in the preparation of soap?

Saponification is the chemical reaction that forms soap. During this procedure, animal or vegetable fat is transformed to soap (a fatty acid) and alcohol. The reaction necessitates the use of an alkali solution in water as well as heat (e.g., sodium hydroxide or potassium hydroxide).

6. Why do detergents work better than soaps in hard water?

Detergents work better in hard water because they don't form insoluble precipitates with calcium and magnesium ions present in hard water. Soaps, on the other hand, form scum (soap scum) in hard water, reducing their cleaning effectiveness.

7. How do biodegradable detergents differ from non-biodegradable ones?

Biodegradable detergents can be broken down by bacteria in the environment, reducing their long-term impact. Non-biodegradable detergents persist in the environment, potentially causing pollution and harm to aquatic life.

8. What role do surfactants play in soaps and detergents?

Surfactants (surface-active agents) are the main active ingredients in soaps and detergents. They lower the surface tension of water, allowing it to spread and wet surfaces more easily, which enhances cleaning power.

9. How do enzyme-based detergents work?

Enzyme-based detergents contain specific enzymes that break down particular types of stains. For example, proteases break down protein-based stains, while lipases target grease and oil stains. This targeted approach enhances cleaning effectiveness.

10. What are some common examples of soaps and detergents?

Common soaps include bar soaps, castile soap, and liquid hand soaps. Examples of detergents include laundry detergents, dish soaps, and shampoos.

11. How do soap-free cleansers work?

Soap-free cleansers, also known as syndets (synthetic detergents), use mild synthetic surfactants instead of traditional soap. They are often gentler on the skin and maintain a pH closer to the skin's natural level.

12. What are soaps and detergents, and how do they differ?

Soaps and detergents are cleaning agents that help remove dirt and grease. Soaps are made from natural fats and oils through saponification, while detergents are synthetic compounds. Detergents work better in hard water and acidic conditions compared to soaps.

13. What is the difference between anionic and cationic detergents?

Anionic detergents have a negatively charged hydrophilic end and are commonly used in laundry detergents. Cationic detergents have a positively charged hydrophilic end and are often used in fabric softeners and disinfectants due to their antimicrobial properties.

14. How do soaps and detergents affect the pH of water?

Soaps are generally alkaline and can increase the pH of water. Most detergents are formulated to be pH-neutral or slightly acidic to match the natural pH of skin and fabrics.

15. What is the purpose of adding optical brighteners to laundry detergents?

Optical brighteners are fluorescent compounds added to laundry detergents. They absorb ultraviolet light and emit blue light, making clothes appear brighter and whiter by counteracting yellowing.

16. What is the difference between liquid and bar soaps in terms of their chemical composition?

Liquid soaps are usually potassium-based, while bar soaps are typically sodium-based. This difference affects their solubility and consistency. Liquid soaps also often contain more water and additional moisturizing ingredients.

17. How do antibacterial soaps differ from regular soaps?

Antibacterial soaps contain additional ingredients like triclosan or benzalkonium chloride that kill or inhibit bacteria. Regular soaps rely on their surfactant properties to remove bacteria physically rather than killing them.

18. How do soaps and detergents affect the surface tension of water?

Soaps and detergents lower the surface tension of water by disrupting the hydrogen bonding between water molecules at the surface. This allows water to spread more easily and penetrate fabrics and surfaces, improving cleaning efficiency.

19. What is the role of builders in laundry detergents?

Builders are additives in laundry detergents that enhance cleaning performance by softening water, maintaining alkalinity, and helping to suspend dirt particles. Common builders include sodium carbonate and zeolites.

20. How do dishwashing detergents differ from laundry detergents?

Dishwashing detergents are typically more alkaline and contain stronger surfactants to cut through grease and food residues. They also often include enzymes specific to breaking down food particles and may have less foaming action compared to laundry detergents.

21. How does the chemical structure of soap molecules allow them to clean?

Soap molecules have a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail. This structure allows them to form micelles around dirt and oil particles, suspending them in water for easy removal.

22. What is saponification, and why is it important in soap-making?

Saponification is the chemical reaction between a fat or oil and an alkali (usually sodium hydroxide) to produce soap. This process is crucial as it creates the soap molecules with their characteristic cleaning properties.

23. How do soaps and detergents affect the hardness of water?

Soaps tend to form insoluble precipitates (soap scum) with hard water minerals, reducing their effectiveness. Detergents, especially those with built-in water softeners, can help reduce water hardness by binding to or sequestering hard water minerals.

24. How do hand sanitizers differ from soaps in their mechanism of action?

Hand sanitizers, typically alcohol-based, kill microorganisms through denaturation of proteins. Soaps, on the other hand, physically remove microorganisms from the skin surface through their surfactant action and the mechanical process of washing.

25. What are the main differences between shampoos and body soaps?

Shampoos are formulated to clean hair and scalp, often with milder surfactants and pH-balanced to match hair's slightly acidic nature. Body soaps are generally more alkaline and may contain harsher surfactants suitable for skin but potentially damaging to hair.

26. Why are phosphates sometimes added to detergents, and what are their environmental impacts?

Phosphates are added to detergents as water softeners and to enhance cleaning power. However, they can cause eutrophication in water bodies, leading to algal blooms and oxygen depletion. Many countries have banned or limited phosphates in detergents due to these environmental concerns.

27. What are the environmental concerns associated with microbeads in some soaps and detergents?

Microbeads are small plastic particles sometimes added to soaps and detergents for exfoliation. They can pass through water treatment plants and end up in water bodies, where they can be ingested by marine life and enter the food chain.

28. How do fabric softeners work, and why are they used separately from detergents?

Fabric softeners contain cationic surfactants that coat fabric fibers, making them feel softer and reducing static cling. They are used separately from detergents because their positive charge can interfere with the negative charge of anionic detergents, reducing cleaning effectiveness.

29. What are the advantages of using cold-water detergents?

Cold-water detergents are formulated to work effectively at lower temperatures. They save energy by reducing the need for hot water, help preserve fabric colors and textures, and can be more environmentally friendly due to reduced energy consumption.

30. What is the purpose of adding fragrances to soaps and detergents?

Fragrances are added to soaps and detergents primarily for consumer appeal, masking unpleasant odors, and creating a sense of cleanliness. However, they can also cause skin irritation in some individuals.

31. What is the significance of the critical micelle concentration (CMC) in detergent solutions?

The critical micelle concentration is the concentration at which detergent molecules begin to form micelles. This is important because micelle formation is crucial for the detergent's cleaning action, trapping oil and dirt particles within the micelles.

32. How do eco-friendly or "green" detergents differ from conventional ones?

Eco-friendly detergents typically use plant-based surfactants, avoid harsh chemicals and phosphates, are often more biodegradable, and may come in concentrated forms to reduce packaging waste. They aim to have a lower environmental impact compared to conventional detergents.

33. What is the role of chelating agents in detergents?

Chelating agents in detergents bind to metal ions in hard water, preventing them from interfering with the cleaning action of surfactants. This improves cleaning efficiency and helps prevent mineral deposits on fabrics and surfaces.

34. How do soaps and detergents affect the surface charge of dirt particles?

Soaps and detergents can alter the surface charge of dirt particles, often making them more negative. This creates electrostatic repulsion between the dirt particles and negatively charged surfaces (like fabrics), helping to keep the dirt suspended in water for removal.

35. What are the potential health concerns associated with certain ingredients in soaps and detergents?

Some ingredients in soaps and detergents, such as certain fragrances, preservatives, and antibacterial agents, can cause skin irritation or allergic reactions in sensitive individuals. There are also concerns about the long-term effects of antibacterial agents like triclosan on antibiotic resistance.

36. How do soaps and detergents interact with the skin's natural oils?

Soaps and detergents can remove some of the skin's natural oils along with dirt and bacteria. This can lead to dryness or irritation, especially with frequent use or harsh formulations. Milder, pH-balanced formulations aim to clean effectively while minimizing disruption to the skin's natural barrier.

37. What is the difference between true soaps and syndet bars?

True soaps are made through the saponification of fats or oils with an alkali. Syndet (synthetic detergent) bars use synthetic surfactants and are typically milder and less alkaline than true soaps, making them potentially less drying to the skin.

38. How do soaps and detergents affect the environment when they enter water systems?

When soaps and detergents enter water systems, they can cause foaming, alter water pH, and contribute to eutrophication. Biodegradable formulations break down more easily, while non-biodegradable components can persist and potentially harm aquatic life.

39. What is the purpose of adding silicates to some detergents?

Silicates are added to some detergents as corrosion inhibitors, protecting washing machine parts from damage. They also act as builders, helping to soften water and enhance cleaning performance.

40. How do soaps and detergents affect the surface properties of fabrics?

Soaps and detergents can alter fabric surface properties by removing dirt and oils, potentially changing the fabric's texture, color, and feel. Some detergents leave residues that can affect fabric properties, while others are designed to maintain or enhance fabric characteristics.

41. What is the role of emulsifiers in soaps and detergents?

Emulsifiers in soaps and detergents help mix oil and water, allowing oily dirt and grease to be suspended in water for easy removal. They work alongside surfactants to enhance the overall cleaning effectiveness.

42. How do soaps and detergents affect the growth of microorganisms?

Regular soaps and detergents can remove microorganisms physically but don't necessarily kill them. Antibacterial soaps and detergents contain specific ingredients that inhibit or kill microorganisms. However, overuse of antibacterial products can potentially lead to antibiotic resistance.

43. What is the difference between soap-based and detergent-based shaving creams?

Soap-based shaving creams are made from saponified fats or oils and tend to be more traditional. Detergent-based shaving creams use synthetic surfactants and are often easier to rinse off. Both types aim to lubricate the skin and soften hair for a smoother shave.

44. How do soaps and detergents interact with different types of stains?

Different types of stains (protein-based, oil-based, etc.) interact differently with soaps and detergents. For example, enzymes in some detergents target specific stain types, while the surfactant action helps lift and suspend various stains in the wash water.

45. What is the purpose of adding optical brighteners to detergents, and how do they work?

Optical brighteners, also known as fluorescent whitening agents, are added to detergents to make clothes appear brighter and whiter. They work by absorbing ultraviolet light and re-emitting it as visible blue light, which counteracts yellowing and gives the impression of increased whiteness.

46. How do soaps and detergents affect the dyeing process of fabrics?

Soaps and detergents can affect fabric dyeing by altering the surface properties of fibers or leaving residues that interfere with dye absorption. In textile processing, special detergents are often used to prepare fabrics for dyeing by removing impurities without leaving interfering residues.

47. What is the role of foam boosters in detergents, and are they necessary for cleaning?

Foam boosters increase the amount of foam produced by detergents, which consumers often associate with cleaning power. However, foam itself is not necessary for cleaning effectiveness. In fact, some high-efficiency washing machines work better with low-foaming detergents.

48. How do soaps and detergents affect the pH balance of skin and hair?

Soaps are typically alkaline and can disrupt the natural acidic pH of skin and hair, potentially leading to dryness or irritation. Many modern detergents and synthetic cleansers are formulated to be pH-balanced or slightly acidic to minimize this disruption.

49. What are the main differences between liquid and powder detergents in terms of their composition and effectiveness?

Liquid detergents typically contain more water and are easier to dissolve, making them effective in cold water. Powder detergents often contain more builders and are generally more effective on ground-in dirt. Liquid detergents are usually better for greasy stains, while powders excel at lifting dirt.

50. How do soaps and detergents affect the surface tension of water, and why is this important for cleaning?

51. What is the purpose of adding enzymes to laundry detergents, and how do they work?

Enzymes are added to laundry detergents to target specific types of stains. For example, proteases break down protein-based stains, lipases target oily stains, and amylases work on starch-based stains. These enzymes catalyze the breakdown of specific molecules, making stains easier to remove during washing.

52. How do soaps and detergents affect the colorfastness of fabrics?

Harsh soaps and detergents can potentially fade or alter fabric colors, especially with repeated use. Many modern detergents are formulated to be color-safe, using gentler surfactants and including ingredients that help protect dyes. However, hot water and excessive washing can still affect colorfastness over time.

53. What is the difference between biodegradable and non-biodegradable surfactants in detergents?

Biodegradable surfactants can be broken down by microorganisms in the environment into simpler, less harmful compounds. Non-biodegradable surfactants persist in the environment and can accumulate, potentially causing long-term ecological issues. Many modern detergents use biodegradable surfactants to reduce environmental impact.

54. How do soaps and detergents interact with different types of fibers (natural vs. synthetic)?

Different fibers interact differently with soaps and detergents. Natural fibers like cotton tend to absorb more water and detergent, while synthetic fibers like polyester are more hydrophobic. This affects how easily stains are removed and how much detergent residue may remain after washing. Detergents are often formulated to work effectively on a range of fiber types.

55. What are the potential long-term effects of using antibacterial soaps and detergents?

Long-term use of antibacterial soaps and detergents may contribute to the development of antibiotic-resistant bacteria. There are also concerns about the environmental impact of antibacterial agents and potential disruption of beneficial bacteria on the skin. Regular soap has been shown to be equally effective for general hygiene purposes in most situations.