SOAPS AND DETERGENTS IMPORTANT NOTES CBSE 10TH IMPORTANT PORTION CHEMISTRY

   

1. What are Soaps?

Soap is a sodium or potassium salt of a long-chain fatty acid.

• Common example: Sodium stearate
  (C₁₇H₃₅COONa)

 Made by:

• Saponification: Reaction of fat/oil + NaOH/KOH → Soap + Glycerol

• Fat/Oil + Alkali (NaOH) → Soap + Glycerol

2. Structure of Soap Molecule

Two parts:

• Hydrophobic (Tail) – long hydrocarbon chain, repels water, attracts dirt/oil.

• Hydrophilic (Head) – ionic part (COO⁻Na⁺), attracts water.

   

STRUCTURE OF SOAP

 3. How Soaps Work

• Dirt/oil is greasy and does not dissolve in water.

• Soap molecules form a micelle:

• Tails trap the dirt/oil.

• Heads face outward, attracting water.

• These micelles lift dirt and rinse it away.

• Micelle: Cluster of soap molecules trapping dirt inside.

4. Limitations of Soaps

• Not effective in hard water (water with Ca²⁺ and Mg²⁺ ions).

• Forms insoluble scum with these ions and reduces cleaning power.

2. Detergents

What are Detergents?

• Detergents are synthetic cleansing agents.

• Made from petrochemicals (not natural fats/oils).

• Example: Sodium lauryl sulfate

Advantages of Detergents

• Work well in hard water

• More foam, more cleaning efficiency

• No scum formation

Types of Detergents

• Anionic – used in laundry (common type)

• Cationic – used in hair conditioners

• Non-ionic – used in dishwashing liquids

Properties of  Soaps and Detergents

   

Feature	Soap

Source

Natural oils/fats

In Hard Water

Forms scum, less effective

Cost

Usually cheaper

Environment

Biodegradable

                      

Feature	Detergent

                               

Source                             Petrochemicals (synthetic)

       

In Hard Water

Works well, no scum

Cost	Often costlier

Environment

Some may not be biodegradable

                             

                                                              

STRUCTURE OF DETERGENT