Lesson Notes By Weeks and Term - Senior Secondary 3

Fats and oils

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TERM׃ IST TERM

WEEK SIX

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Chemistry

Topic: Fats and oil

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

  1. identify the sources of fats and oils
  2. Identify the properties of fats and oils.
  3. Describe the reaction of fats and oils (saponification)
  4. Identify the uses of fats and oils

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 introduces fats and oil and guides students to identify the sources of fats and oils.

 

Students pay

attention

STEP 2

EXPLANATION

Teacher perform simple demonstrations to show the properties of fats and oil.

Students pay

attention and

participate

 

STEP 3

DEMONSTRATIO

N

Teacher discusses the reaction of fats and oils (saponification) and explain the uses of fats and oils.

 

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

FATS AND OIL

Fats and oils belong to a general group of compounds known as lipids. Fats are solids usually of animal origin while oils are liquids mainly from plants. Both are esters of the trihydric alkanol, propane-1,2,3-triol. Each molecule of propane-1,2,3,-triol is esterified with three molecules of fatty acids as follows

Sources of Fats and Oils

   - Fats and oils are found in both plant and animal sources.

   - Plant sources include seeds, nuts, olives, and avocados.

   - Animal sources include meat, fish, and dairy products.

Physical properties of fats and oil.

  1. State at Room Temperature:

   - Fats are typically solid at room temperature.

   - Oils are liquid at room temperature.

  1. Melting Point:

   - Fats have a higher melting point due to their solid state.

   - Oils have a lower melting point, remaining liquid at room temperature.

  1. Solubility:

   - Fats and oils are insoluble in water.

   - They are soluble in organic solvents like ether and chloroform.

  1. Density:

   - Fats are denser than oils due to their solid nature.

   - Oils have a lower density because they are in a liquid state.

  1. Odor and Flavor:

   - Both fats and oils may carry specific odors and flavors based on their source and processing methods.

  1. Color:

   - The color of fats and oils can vary, ranging from clear to yellow or brown, depending on factors such as impurities, processing, and source.

Chemical properties of fats and oils

  1. Fats and oils can undergo hydrolysis, a chemical reaction where they react with water in the presence of an acid or base to break down into glycerol and fatty acids.

   Triglyceride + 3H2O Glycerol + 3Fatty Acids

  1. Saponification is a reaction with a strong base (such as sodium hydroxide or potassium hydroxide) to produce soap and glycerol.

   Triglyceride  + 3NaOH  Glycerol + 3Soap Molecules

  1. Polymerization:

   - Under certain conditions, fatty acids in fats and oils can undergo polymerization, forming polymers. This process is often undesirable, as it can affect the quality of the fat or oil.

  1. Isomerization reactions can occur in unsaturated fatty acids, leading to the conversion of cis-isomers to trans-isomers. Trans fats are associated with health concerns.

Reactions of Fats and Oils (Saponification)

 The saponification reaction involves the hydrolysis of fats and oils in the presence of a strong base, usually sodium hydroxide (NaOH) or potassium hydroxide (KOH). This reaction results in the formation of soap and glycerol.

The general equation for saponification is:

Triglyceride + 3NaOH  Glycerol + 3Soap Molecules

Also,  considering a specific example with a triglyceride called stearin:

  Stearin (C57H110O6) + 3NaOH  Glycerol (C3H8O3) + 3Sodium stearate(Soap)

Here, stearin, which is a triglyceride, reacts with three molecules of sodium hydroxide to produce glycerol and three molecules of sodium stearate, which is the sodium salt of stearic acid. The sodium stearate formed is the soap.

This process is essential in soap-making industries, where natural fats or oils are often used as raw materials to produce soap through saponification.

Uses of fats and oils

   - Fats and oils serve as a concentrated source of energy in the diet.

   - They are used in cooking for frying, baking, and as ingredients in various dishes.

   - Fats and oils find applications in industries such as soap making, cosmetics, and lubricants.

   - They are used in food processing for flavor, texture, and shelf life enhancement.

   - Fats play a crucial role in the body, including insulation, protection of organs, and absorption of fat-soluble vitamins.

EVALUATION:   1. Mention three sources of fats and oils

  1. What is saponification, describe how saponification takes place
  2. Identify 4 uses of fats and oils

CONCLUSION: The teacher commends the students positively