Lesson Notes By Weeks and Term - Senior Secondary 2

Qualitative and quantitative analysis 4

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TERM׃ 3RD TERM

WEEK ELEVEN

Class: Senior Secondary School 2

Age: 16 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Chemistry

Topic:- Qualitative and quantitative analysis 4

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

  1. Test for the presence of simple elements like hydrogen.and oxygen.
  2. Carry out test to identify fats and oils, Simple sugy, protein and starch.

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 explain the characteristics of elements/compounds to be tested to the students, then assist them to carry out the test..

Students pay

attention

STEP 2

EXPLANATION

Teacher aid students to carry out test on fat and oils, sugar, protein and starch.

 

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

QUANTITATIVE AND QUALITATIVE ANALYSIS 4

  1. Test for hydrogen, NH3, HCl, NO3, Oxygen, CO2, Cl (bleaching action)

Below is a table for the tests of Hydrogen, NH3, HCl, NO3, Oxygen, CO2, and Cl:

Substance

Test/Identification Method

Result indicating presence

 Hydrogen    

Burning splint       

Squeaky pop sound 

NH3 (Ammonia)   

Smell   

Distinct, pungent odor        

 HCl (Hydrochloric Acid)

Blue litmus paper  

Turns red 

NO3 (Nitrate ions)

 Nitric acid + Silver nitrate

White precipitate         

 Oxygen      

 Glowing splint     

Relights       

CO2 (Carbon Dioxide)

Limewater      

 Turns milky

Cl (Bleaching Action)

Damp litmus paper

Red to bleached (indicating bleaching action of Cl)

 

NOTE: This table summarizes the specific tests and results for each substance.

  1. Identification of fats and oils, simple sugar, proteins, starch.

For fats and oils.

To identify fats and oils, you can perform a variety of chemical tests. Here are a few commonly used methods:

  1. Grease Spot Test:

   - Apply a small amount of the substance onto a piece of paper.

   - Allow it to dry.

   - If the spot is translucent or leaves a greasy mark, it indicates the presence of fats or oils.

  1. Solubility Test:

   - Fats and oils are generally insoluble in water but soluble in organic solvents like ether or hexane.

   - Dissolve a small amount of the substance in the solvent, and observe its solubility.

  1. Saponification Test:

   - Mix the substance with sodium hydroxide (NaOH) solution.

   - If soap (sodium salt) is formed, it confirms the presence of fats or oils.

For simple sugar

The identification of simple sugars can be done through various chemical tests. One common test is the Benedict's Test:

  1. Benedict's Test:

   - Mix a small amount of the substance with Benedict's reagent (copper sulfate solution with sodium citrate).

   - Heat the mixture in a boiling water bath.

   - If simple sugars (reducing sugars) are present, a color change will occur. A green, yellow, orange, or red precipitate indicates the presence and concentration of reducing sugars.

NOTE: That Benedict's test is specific to reducing sugars like glucose and fructose. Other tests, such as Fehling's test, can also be used for the identification of reducing sugars.

For protein

Proteins can be identified through the Biuret Test:

  1. Biuret Test:

   - Mix a small amount of the substance with dilute copper sulfate solution.

   - Add sodium hydroxide (NaOH) to make the solution alkaline.

   - If proteins are present, a violet color change will occur.

NOTE : This test detects the peptide bonds in proteins. The intensity of the violet color is proportional to the protein concentration.

Identification of starch

To identify the presence of starch, you can perform the Iodine Test:

  1. Iodine Test:

   - Place a small amount of the substance on a surface (e.g., a white plate or paper).

   - Add a few drops of iodine solution (iodine dissolved in potassium iodide).

   - If starch is present, the mixture will turn from brown to a distinct blue-black color.

This reaction occurs due to the formation of a starch-iodine complex, resulting in the characteristic color change.

EVALUATION:   - Discuss the test for hydrogen.

                              - Explain how saponification Test is carried out.

 CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively