Lesson Notes By Weeks and Term - Senior Secondary 3
Soap and detergents 1
Soap and detergents 1
TERM׃ IST TERM
WEEK SEVEN
Class: Senior Secondary School 3
Age: 17 years
Duration: 40 minutes of 5 periods each
Date:
Subject: Chemistry
Topic: Soap and Detergent 1
SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to
INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,
demonstration, videos from source
INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures, Vegetable oil, Caustic soda or potash, Wood ash, Containers/reaction vessels.
INSTRUCTIONAL PROCEDURES
PERIOD 1-2
|
PRESENTATION |
TEACHER’S ACTIVITY |
STUDENT’S ACTIVITY |
|
STEP 1 INTRODUCTION |
The teacher explains the preparation of soap to the students. |
Students pay attention |
|
STEP 2 EXPLANATION |
Teacher describe the cleaning action of soap and explain the steps involved. |
Students pay attention and participate |
|
STEP 3 NOTE TAKING |
The teacher writes a summarized note on the board
|
The students copy the note in their books |
NOTE
SOAP AND DETERGENT 1
Preparation of soap
The preparation of soap involves the saponification reaction, where fats or oils react with a strong base (alkali), such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), to produce soap and glycerol. Here is a simplified equation:
Triglyceride + 3NaOH 
Glycerol + 3Soap Molecules
For a more specific example, let's consider the saponification of a common fat, such as coconut oil, which contains a mixture of fatty acids:
Coconut Oil (C12H24O2) + 3NaOH Glycerol(C3H8O3) + 3Sodium Fatty Acid Salts(Soap)
In this reaction, coconut oil, which is a triglyceride, reacts with three molecules of sodium hydroxide to produce glycerol and three molecules of sodium fatty acid salts, which are the soap molecules.
NOTE: The soap molecules have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail, allowing them to interact with both water and grease. This makes soap an effective cleaning agent, as it can emulsify and lift away oily or greasy substances in the presence of water.
Structure of Soap
The structure of soap molecules consists of two main parts: a hydrophilic (water-attracting) "head" and a hydrophobic (water-repelling) "tail." This dual nature allows soap molecules to interact with both water and oils, making them effective in cleaning. The typical structure of a soap molecule is illustrated below:
Action of soap as emulsifying agents
Soap acts as an emulsifying agent due to its unique molecular structure. The hydrophilic (water-attracting) and hydrophobic (water-repelling) parts of soap molecules enable them to interact simultaneously with both water and oily substances. The steps describe how soap functions as an emulsifying agent:
- The hydrophilic head of the soap molecule is attracted to water molecules, allowing it to be soluble in water.
- The long hydrophobic tail of the soap molecule is repelled by water but is attracted to oils and grease.
- When soap is added to water containing oils or grease, the soap molecules arrange themselves into structures called micelles.
- In a micelle, the hydrophobic tails cluster together in the center, shielding themselves from water, while the hydrophilic heads face outward, interacting with water molecules.
- The hydrophobic tails of the soap molecules embed into the oil or grease, forming a core within the micelle.
- The hydrophilic heads on the outer surface of the micelle interact with water, keeping the entire structure suspended in the water.
NOTE: This emulsifying action allows soap to surround and disperse oily substances in water, forming stable emulsions. These emulsions can then be easily rinsed away, carrying the trapped grease with them. This property makes soap an effective cleaner for removing oils, fats, and other hydrophobic substances from surfaces.
EVALUATION: 1. Discuss the preparation of soap.
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively