Lesson Note on Alkanols: Meaning, Preparation, Fermentation and Uses for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 1st Term
Week: 1
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Organic Chemistry
Previous Lesson: .
Topic: ALKANOLS
Subject Matter: Meaning of alkanols (alcohols, organic compounds containing the hydroxyl group -OH), types and properties, preparation and properties of alkanols, industrial production of alkanols by fermentation, etherification, uses of alkanols.

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

• Define alkanols and identify their functional group.
• State different types of alkanols based on the position of the hydroxyl group.
• Describe the general physical and chemical properties of alkanols.
• Explain the industrial production of alkanols by fermentation and etherification.
• List various uses of alkanols in daily life and industry.

Affective Domain:

• Appreciate the importance of alkanols in various applications.
• Observe safety precautions when handling chemical reagents.
• Show interest in learning about organic compounds.

Psychomotor Domain:

• Conduct simple tests to show the solubility of alkanols in water.
• Write balanced chemical equations for the reactions of alkanols, such as oxidation and dehydration.
• Record observations accurately during practical demonstrations.

Social Domain:

• Collaborate effectively during group observations and discussions.
• Share ideas and observations with peers.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• New School Chemistry for Senior Secondary Schools by Osei Yaw Ababio

Instructional Materials

The teacher will teach this lesson with the aid of:

• Ethanol
• Potassium permanganate (KMnO4) solution
• Water
• Concentrated tetraoxosulphate(VI) acid (H2SO4)
• Test tubes
• Test-tube racks
• Sodium metal

Rationale for the Lesson

This lesson helps pupils understand a significant class of organic compounds, alkanols, which are common in everyday life and industry. Learning about alkanols enables pupils to grasp fundamental concepts in organic chemistry and appreciate their practical applications.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of hydrocarbons, functional groups, and basic chemical reactions from previous lessons in organic chemistry.

Lesson Content/Board Summary

ALKANOLS

Meaning of Alkanols

Alkanols, also known as alcohols, are organic compounds that contain the hydroxyl functional group (-OH) attached to a saturated carbon atom. Their general formula is CnH2n+1OH, where ‘n’ represents the number of carbon atoms.

Types of Alkanols

Alkanols are classified based on the number of alkyl groups attached to the carbon atom bearing the hydroxyl group:

• Primary Alkanols (1°): The carbon atom attached to the -OH group is bonded to only one other alkyl group (e.g., ethanol, CH3CH2OH).
• Secondary Alkanols (2°): The carbon atom attached to the -OH group is bonded to two other alkyl groups (e.g., propan-2-ol, CH3CH(OH)CH3).
• Tertiary Alkanols (3°): The carbon atom attached to the -OH group is bonded to three other alkyl groups (e.g., 2-methylpropan-2-ol, (CH3)3COH).

General Properties of Alkanols

1. Physical Properties:

• Lower alkanols (methanol, ethanol) are colourless, volatile liquids with characteristic smells.
• They are soluble in water due to hydrogen bonding between the -OH group and water molecules. Solubility decreases as the carbon chain length increases.
• They have higher boiling points compared to alkanes of similar molecular mass due to hydrogen bonding.

2. Chemical Properties:

• Combustion: Alkanols burn in air to produce carbon dioxide and water.
  Example: CH3CH2OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)
• Reaction with Sodium: Alkanols react with active metals like sodium to produce hydrogen gas and an alkoxide.
  Example: 2CH3OH(l) + 2Na(s) → 2CH3ONa(aq) + H2(g)
• Oxidation:
  • Primary alkanols oxidize to alkanals (aldehydes) and further to alkanoic acids (carboxylic acids).
    Example: CH3CH2OH –[KMnO4/H+]–> CH3CHO –[KMnO4/H+]–> CH3COOH
  • Secondary alkanols oxidize to alkanones (ketones).
    Example: CH3CH(OH)CH3 –[KMnO4/H+]–> CH3COCH3
  • Tertiary alkanols are resistant to oxidation under normal conditions.
• Dehydration (Elimination of Water): Alkanols can lose water in the presence of concentrated H2SO4 to form alkenes or ethers, depending on the temperature.
  • Formation of Alkenes (at high temperature, ~170°C):
    Example: CH3CH2OH –[Conc. H2SO4, 170°C]–> CH2=CH2 + H2O
  • Formation of Ethers (at lower temperature, ~140°C):
    Example: 2CH3CH2OH –[Conc. H2SO4, 140°C]–> CH3CH2OCH2CH3 + H2O

Industrial Preparation of Alkanols

1. Fermentation: This is the biochemical process where yeast (containing zymase enzyme) converts sugars (e.g., glucose) into ethanol and carbon dioxide in the absence of oxygen.
Example: C6H12O6(aq) –[Yeast]–> 2CH3CH2OH(aq) + 2CO2(g)

2. Etherification (Hydration of Alkenes): Ethene (an alkene) reacts with steam (water) in the presence of a phosphoric(V) acid catalyst at high temperature and pressure to produce ethanol.
Example: CH2=CH2(g) + H2O(g) –[H3PO4, high T/P]–> CH3CH2OH(g)

Uses of Alkanols

Alkanols have various uses, including:

• As solvents for paints, varnishes, and perfumes.
• In the production of alcoholic beverages (ethanol).
• As fuel (e.g., gasohol, a blend of gasoline and ethanol).
• In the manufacture of ethanoic acid, esters, and other organic compounds.
• As antiseptics and disinfectants (e.g., hand sanitizers).
• In thermometers (methanol).

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to name some common liquids they use at home or see in everyday life that might contain alcohol, such as hand sanitizers or alcoholic beverages.
Pupils’ Activity: Pupils respond by naming liquids like hand sanitizers, beer, or spirits.
Learning Point: Pupils connect the topic to their prior knowledge and everyday experiences.

Step 2: Meaning and Types of Alkanols

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines alkanols as organic compounds containing the hydroxyl (-OH) group and explains their general formula. The teacher then discusses the classification of alkanols into primary, secondary, and tertiary based on the position of the -OH group.
Pupils’ Activity: Pupils listen attentively, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definition and classification of alkanols.

Step 3: Physical Properties of Alkanols

Time: 7 minutes
Teaching Skill: Demonstration/Observation
Teacher’s Activity: The teacher demonstrates the solubility of methanol and ethanol in water by mixing them in different ratios in test tubes. The teacher highlights observations and explains the role of hydrogen bonding in solubility and boiling points.
Pupils’ Activity: Pupils observe the demonstration, record their observations, and confirm the solubility of methanol and ethanol in water.
Learning Point: Pupils learn about the physical properties of alkanols, especially their solubility.

Step 4: Chemical Reactions: Oxidation of Alkanols

Time: 7 minutes
Teaching Skill: Experimentation/Explanation
Teacher’s Activity: The teacher performs an experiment showing the oxidation of an alkanol (e.g., ethanol) using acidified potassium permanganate (KMnO4). The teacher observes the colour change (purple to colourless/brown) and explains the products formed for primary and secondary alkanols.
Pupils’ Activity: Pupils observe the experiment, record the results (colour change), and note the products formed during the oxidation of alkanols.
Learning Point: Pupils understand the oxidation reaction of alkanols and its products.

Step 5: Chemical Reactions: Reaction with Sodium and Dehydration

Time: 7 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher carefully demonstrates the action of sodium metal on methanol, showing effervescence (hydrogen gas production). The teacher then explains the dehydration reaction of alkanols, showing how alkenes and ethers are formed under different temperature conditions with concentrated H2SO4.
Pupils’ Activity: Pupils observe the reaction with sodium, describe the observations, and write simple equations for dehydration reactions.
Learning Point: Pupils learn about the reaction of alkanols with sodium and their dehydration reactions.

Step 6: Industrial Preparation and Uses of Alkanols

Time: 5 minutes
Teaching Skill: Lecture/Discussion
Teacher’s Activity: The teacher explains the industrial production methods of alkanols, focusing on fermentation of sugars and the etherification (hydration) of alkenes. The teacher also discusses the various uses of alkanols in different sectors.
Pupils’ Activity: Pupils listen, take notes, and contribute to the discussion on the uses of alkanols.
Learning Point: Pupils understand how alkanols are produced industrially and their practical applications.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Define alkanols and state their general formula.
2. List two types of alkanols.
3. Describe what happens when sodium metal reacts with methanol.
4. State two industrial uses of ethanol.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, emphasizing the definition, types, properties, preparation, and uses of alkanols. The teacher assigns homework, asking pupils to research the health effects of excessive consumption of ethanol.
Pupils’ Activity: Pupils listen to the summary and copy down the homework assignment.
Learning Point: Pupils consolidate their understanding of alkanols.

Lesson Keywords

• Alkanols – Organic compounds containing the hydroxyl (-OH) functional group.
• Hydroxyl group – The -OH functional group characteristic of alcohols.
• Fermentation – Biochemical process converting sugar to ethanol and CO2 using yeast.
• Dehydration – Reaction involving the removal of water from a molecule.
• Oxidation – Reaction involving the gain of oxygen or loss of hydrogen/electrons.
• Alkoxide – The product formed when an alkanol reacts with an active metal.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional complex reaction mechanisms or ask them to research more advanced applications of alkanols. For pupils needing more support, the teacher can provide simplified notes, focus on basic definitions and uses, and offer one-on-one guidance during practical observations.

Note for teachers using this lesson plan

Ensure all chemical demonstrations are conducted with appropriate safety precautions, including wearing safety goggles and working in a well-ventilated area. Emphasize the dangers of methanol consumption. Encourage pupils to write balanced chemical equations for all reactions discussed.