Lesson Note on Electric Field: Electrolysis, Faraday’s Law and Applications for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 3rd Term
Week: 1
Age: 16 years
Duration: 45 minutes
Subject: Physics
Curriculum Theme: Electricity and Magnetism
Previous Lesson: .
Topic: Electrical Conduction Through Liquids (Electrolysis)
Subject Matter: Electrical conduction through liquids electrolysis (meaning), electrolytes and non-electrolytes (definitions and examples), dynamics of charged particles ions in electrolytes (movement in solution), voltammeter (use in electrolysis), examples of electrolysis (acidified water, brine, and more), Faraday’s law of electrolysis (statement), applications of electrolysis (electroplating, purification, extraction).

Specific Objectives

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

Cognitive Domain:

• Define electrolysis, electrolytes, and non-electrolytes.
• State Faraday’s laws of electrolysis.
• Explain the principle of electrical conduction through liquids.

Affective Domain:

• Appreciate the industrial importance of electrolysis.
• Recognize the relevance of electrolysis in everyday life.

Psychomotor Domain:

• Classify different solutions as electrolytes or non-electrolytes.
• Describe the movement of ions in an electrolyte during current flow.
• Identify the main components and use of a voltameter.

Social Domain:

• Discuss various applications of electrolysis.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• New School Physics for Senior Secondary Schools by M.W. Anyakoha
• Links for Reference materials: [Insert relevant links here]

Instructional Materials

The teacher will teach this lesson with the aid of:

• Textbook
• Charts showing electrolysis setup and applications
• Equipped laboratory (if available, for demonstration of conductivity tests)

Rationale for the Lesson

This lesson helps pupils understand how electricity can pass through certain liquids and the chemical changes that occur. It enables pupils to see the practical importance of these processes in industries like metal refining and coating objects.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of electric current, conductors, insulators, and the composition of solutions.

Lesson Content/Board Summary

Electrical Conduction Through Liquids (Electrolysis)

Meaning of Electrolysis

Electrolysis is the process by which an electric current is passed through a substance to effect a chemical change. This chemical change involves the decomposition of the substance.

Electrolytes and Non-electrolytes

Electrolytes: These are substances (usually in molten state or aqueous solution) that conduct electricity due to the movement of free ions and are chemically decomposed in the process.
The following are examples of electrolytes:

• Acids (e.g., dilute H₂SO₄, HCl)
• Bases (e.g., NaOH, KOH)
• Salts (e.g., molten NaCl, aqueous CuSO₄)

Non-electrolytes: These are substances that do not conduct electricity in molten state or aqueous solution. They do not contain free ions.
The following are examples of non-electrolytes:

• Distilled water
• Sugar solution
• Ethanol
• Kerosene

Dynamics of Charged Particles (Ions) in Electrolytes

When an electric current passes through an electrolyte, the electrolyte dissociates into positively charged ions (cations) and negatively charged ions (anions).
Cations move towards the negatively charged electrode (cathode), where they gain electrons and are discharged.
Anions move towards the positively charged electrode (anode), where they lose electrons and are discharged.

Voltameter

A voltameter (or electrolytic cell) is an apparatus used to carry out electrolysis. It consists of two electrodes (anode and cathode) immersed in an electrolyte, connected to an external DC power supply.

Examples of Electrolysis

1. Electrolysis of Acidified Water:

Acidified water (e.g., water with a few drops of H₂SO₄) is used because pure water is a poor conductor.
At Cathode (negative electrode): 4H⁺(aq) + 4e⁻ → 2H₂(g) (Hydrogen gas is produced)
At Anode (positive electrode): 4OH⁻(aq) → O₂(g) + 2H₂O(l) + 4e⁻ (Oxygen gas is produced)
Overall Reaction: 2H₂O(l) → 2H₂(g) + O₂(g)

2. Electrolysis of Brine (Concentrated Sodium Chloride Solution):

At Cathode (negative electrode): 2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq) (Hydrogen gas is produced)
At Anode (positive electrode): 2Cl⁻(aq) → Cl₂(g) + 2e⁻ (Chlorine gas is produced)
Sodium hydroxide (NaOH) is left in the solution.

Faraday’s Laws of Electrolysis

First Law of Electrolysis:
The mass (m) of a substance liberated or deposited at an electrode during electrolysis is directly proportional to the quantity of electricity (Q) passed through the electrolyte.
Mathematically: m ∝ Q, or m = ZQ, where Z is the electrochemical equivalent.

Second Law of Electrolysis:
When the same quantity of electricity is passed through different electrolytes connected in series, the masses of the substances liberated or deposited at the respective electrodes are directly proportional to their chemical equivalents (or equivalent weights).

Applications of Electrolysis

The following are important applications of electrolysis:

• Electroplating: Coating a metal object with a thin layer of another metal for protection or decoration (e.g., silver plating, chromium plating).
• Purification of Metals: Refining impure metals to obtain highly pure metals (e.g., purification of copper).
• Extraction of Metals: Obtaining reactive metals from their molten ores (e.g., extraction of aluminium from bauxite, sodium from molten NaCl).
• Electrotyping: Producing copies of objects.
• Anodizing: Forming a protective oxide layer on metal surfaces.

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 asks pupils to name some materials that conduct electricity and those that do not. The teacher then asks if liquids can conduct electricity.
Pupils’ Activity: Pupils respond by naming conductors (e.g., copper, iron) and insulators (e.g., plastic, wood), and offer ideas on liquid conductivity.
Learning Point: Pupils recall prior knowledge of electrical conductors and insulators, leading to the concept of liquid conductivity.

Step 2: Explanation of Electrolysis and Electrolytes

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines electrolysis and explains that only certain liquids (electrolytes) conduct electricity due to the presence of free ions, giving examples.
Pupils’ Activity: Pupils listen attentively, take notes, and identify examples of electrolytes.
Learning Point: Pupils understand the meaning of electrolysis and can identify electrolytes.

Step 3: Non-electrolytes and Dynamics of Ion Movement

Time: 8 minutes
Teaching Skill: Classification/Illustration
Teacher’s Activity: The teacher defines non-electrolytes with examples and then explains how ions move towards respective electrodes (anode and cathode) during the process of electrolysis.
Pupils’ Activity: Pupils differentiate between electrolytes and non-electrolytes and describe the movement of cations and anions.
Learning Point: Pupils can classify non-electrolytes and understand the mechanism of ion movement during electrolysis.

Step 4: Voltameter and Examples of Electrolysis

Time: 8 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher describes the voltameter and its components using a chart. The teacher then explains the electrolysis of acidified water and brine, outlining the reactions at the electrodes.
Pupils’ Activity: Pupils observe the chart, ask questions, and note the reactions for the given examples.
Learning Point: Pupils understand the setup for electrolysis and specific examples of the process.

Step 5: Faraday’s Laws of Electrolysis

Time: 5 minutes
Teaching Skill: Stating Laws
Teacher’s Activity: The teacher states Faraday’s First and Second Laws of Electrolysis clearly.
Pupils’ Activity: Pupils listen, write down the laws, and ask for clarification if needed.
Learning Point: Pupils learn the fundamental laws governing quantitative aspects of electrolysis.

Step 6: Applications of Electrolysis

Time: 4 minutes
Teaching Skill: Discussion/Application
Teacher’s Activity: The teacher discusses practical applications of electrolysis such as electroplating, purification of metals, and extraction of reactive metals, relating them to real-life uses.
Pupils’ Activity: Pupils contribute to the discussion by mentioning other applications they know and take notes on the explained applications.
Learning Point: Pupils understand the practical and industrial importance of electrolysis.

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 electrolysis.
2. Distinguish between electrolytes and non-electrolytes, giving two examples for each.
3. State Faraday’s First Law of Electrolysis.
4. Mention three applications of electrolysis.

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 importance of electrolysis. The teacher then gives homework: “Draw a labelled diagram of a voltameter and explain its function.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their understanding of the topic and prepare for further study.

Lesson Keywords

• Electrolysis – The chemical decomposition of a substance by an electric current.
• Electrolyte – A substance that conducts electricity in molten or solution state and is decomposed in the process.
• Non-electrolyte – A substance that does not conduct electricity.
• Anode – The positive electrode in an electrolytic cell where oxidation occurs.
• Cathode – The negative electrode in an electrolytic cell where reduction occurs.
• Ion – An atom or molecule with an electric charge due to the loss or gain of one or more electrons.
• Voltameter – An apparatus used for carrying out electrolysis.
• Faraday’s Laws – Quantitative laws describing the amount of chemical change produced by electric current during electrolysis.
• Electroplating – The process of coating an object with a thin layer of metal using electrolysis.
• Purification – The process of removing impurities from a substance.
• Extraction – The process of obtaining a substance from its source.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional complex examples of electrolysis or ask them to research other industrial applications. For pupils who need more support, the teacher can provide simplified diagrams, review definitions individually, or offer guided practice with identifying electrolytes and non-electrolytes.

Note for teachers using this lesson plan

Ensure pupils understand the difference between metallic conduction (electron flow) and electrolytic conduction (ion flow). If a laboratory demonstration is not possible, use clear diagrams and videos to illustrate the process of electrolysis and the movement of ions. Emphasize the practical relevance of electrolysis to keep pupils engaged.