Lesson Notes By Weeks and Term - Senior Secondary 3

Soap and detergents 2

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TERM׃ IST TERM

WEEK EIGHT

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Chemistry

Topic: Soap and Detergent 2

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Describe the preparation of detergents
  2. Discuss the mode of action of detergents.
  3. Identify the difference between soap and detergents

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

 

STEP 1

INTRODUCTION

The teacher explains the preparation process of detergents to the students

 

Students pay

attention

STEP 2

EXPLANATION

Teacher explains the mode of action of detergents

Students pay

attention and

participate

 

STEP 3

DEMONSTRATIO

N

Teacher discusses the difference between soap and detergents

 

Students pay

attention and

participate

STEP 4

NOTE TAKING

The teacher writes a summarized

note on the board

 

The students

copy the note in

their books

NOTE

SOAP AND DETERGENT 2

Preparation of detergents

The preparation of detergents involves complex chemical processes, and providing detailed equations can be quite extensive. However,  below is a simplified overview;

  1. Saponification:

Fatty Acid + Base Soap + Glycerol

   - Explanation: Fatty acids react with a base (usually sodium hydroxide or potassium hydroxide) to form soap and glycerol.

  1. Sulphonation:

Hydrocarbon + SO3   Sulphonate

   - Explanation: Hydrocarbons undergo sulphonation with sulfur trioxide to produce sulphonates, which are important surfactants.

  1. Neutralization:

   Sulphonic Acid + Base  Detergent  + Water

   - Explanation: Sulphonic acid reacts with a base to neutralize and form a detergent, often in the form of sodium salts.

NOTE: The actual industrial processes involve multiple steps and variations depending on the specific detergent being produced.

Mode of action of detergents

Detergents function by emulsifying and dispersing dirt and grease. The key modes of action include:

  1. Emulsification and Dispersing:

    Detergent  +  Oil  Emulsion

   - Explanation: Detergents surround oil, breaking it into small droplets (emulsification) and preventing these droplets from reattaching to surfaces (dispersing).

  1. Surfactant Action:

Surfactant  + Water  +  Dirt  Micelles

   - Explanation: Surfactants in detergents form micelles that encapsulate dirt particles, allowing them to be suspended in water and easily washed away.

  1. Ion Exchange (Hard Water):

    Builder + Ca2+  Complex

   - Explanation: Detergents with builders sequester calcium ions in hard water, preventing them from interfering with the detergent action.

Differences between soap and detergents

Below is a summary of the main differences between soap and detergents:

 Characteristic

Soap 

Detergent                            

Composition

Natural fats or oils with alkali    

Synthetic compounds, often petrochemical-based

Formation of Scum

 Can form scum in hard water          

Generally does not form scum in hard water due to added builders

Biodegradability

Generally more biodegradable    

Varies; some detergents may be less biodegradable

 Effectiveness in Hard Water

Less effective due to soap scum

Often more effective, as many contain water-softening agents

Source

Traditionally derived from natural sources

Synthetically manufactured   

 

EVALUATION:   1. Identify 4 difference between soap and detergents

  1. Discuss briefly, the preparation of detergents
  2. Describe the mode of action of soap and detergents

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively