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Questions
Describe in brief the cleansing action of soap.
Explain the cleansing action of soaps.
Explain the mechanism of the cleaning action of soaps.
Solution 1
Cleansing action of soaps:
The dirt present on clothes is organic in nature and is insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water and, thus, the dust particles are easily rinsed away by water.
Solution 2
The cleaning action of soap can be described as follows:
- A soap molecule has a tadpole-shaped structure.
- At one end (long, non-polar end) of the soap molecule is a hydrocarbon chain which is insoluble in water but soluble in oil.
- At the other end (short polar end) of the soap molecule, there is a carboxylate ion which is hydrophilic, i.e. water soluble but insoluble in oil.
- Soap, on mixed with water, forms a concentrated solution and causes foaming.
- The long non-polar end of soap gravitates towards and surrounds the dirt and absorbs the dust in it.
- The short polar end with the carboxylate ion repels the water away from the dirt.
- A spherical aggregate of soap molecules is formed in the soap solution in water and is called a micelle.
- Thus, the soap molecule dissolves the dirt and our clothes get clean.
Formation of micelles
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RELATED QUESTIONS
Both soap and detergent are some type of salts. What is the difference between them?
Why do soaps not form lather in hard water?
List two problems that arise due to the use of detergents instead of soaps.
Which of the following sets of materials can be used for conducting a saponification reaction for the preparation of soap?
(a) Ca(OH)2 and neem oil
(b) NaOH and neem oil
(c) NaOH and mineral oil
(d) Ca(OH)2 and mineral oil
Would you be able to check if water is hard by using a detergent?
While studying the saponification reaction, what do you observe when you mix an equal amount of colourless vegetable oil and 20% aqueous solution of NaOH in a beaker?
(A) The colour of the mixture has become dark brown
(B) A brisk effervescence is taking place in the beaker
(C) The outer surface of the beaker has become hot
(D) The outer surface of the beaker has become cold
The soap molecule has a ______.
A student is testing water to know which is best for cleansing purposes with soaps. He would find that the cleansing action of soaps is best when he uses water obtained from
(a) rain
(b) tap
(c) hand pump
(d) pond
What is the difference between the chemical composition of soaps and detergents? State in brief the action of soaps in removing an oily spot from a shirt. Why are sops not considered suitable for washing where water is hard?
Why are soaps not suitable for washing clothes when the water is hard?
What is meant by 'surface activity'?
Write an answer to the following question.
Name three chemicals responsible for the surface activity of various detergents.
What are the differences between Bath soap and soap for washing clothes?
Explain why often coloured spots are formed on clothes during washing.
Soaps were originally made from ______.
Match the following
| 1. | Soap | C6H5 OH |
| 2. | Cement | CaSO4.2H2O |
| 3. | Fertilizers | NaOH |
| 4. | Gypsum | RCC |
| 5. | Phenol | NPK |
Arrange the following statements in correct sequence
- Pour that solution into an empty matchbox, soap can be obtained after drying.
- Take the necessary quantity of water in a jar.
- Then add coconut oil drop by drop and stir it well.
- Add concentrated sodium hydroxide in the jar and allow it to cool.
- Try this soap to wash your hand kerchief.
- Cover your work area with old newspaper.
