Lesson Note on Ionic Theory: Meaning, Electrolytes and Electrochemical Series for SSS 2

Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 3rd Term
Week: 5
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Chemical Reactions and Stoichiometry
Previous Lesson: Redox Reactions: Agents, IUPAC Names and Balancing Equations.
Topic: IONIC THEORY
Subject Matter: Meaning of ionic theory (explanation of substances in terms of ions in solution), electrovalent and covalent compounds, electrolytes and non-electrolytes, weak and strong electrolytes, electrochemical series, factors affecting the preferential discharge of ions.

Specific Objectives

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

Cognitive Domain:

• Define ionic theory.
• Distinguish between electrovalent and covalent compounds.
• Differentiate between electrolytes and non-electrolytes.
• Compare strong and weak electrolytes.
• Explain the electrochemical series.
• Identify factors affecting the preferential discharge of ions.

Affective Domain:

• Appreciate the importance of ions in chemical reactions.
• Value the role of electrolytes in various applications.
• Show interest in understanding the principles of electrochemistry.

Psychomotor Domain:

• Classify given substances as electrolytes or non-electrolytes.
• Predict the preferential discharge of ions using the electrochemical series.
• Observe and describe experiments related to strong and weak electrolytes.

Social Domain:

• Participate actively in class discussions about ionic theory.
• Collaborate with peers to identify different types of compounds and electrolytes.
• Communicate their understanding of electrochemical principles clearly.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• Essential Chemistry for Senior Secondary Schools by O.A. Osei Yaw
• https://nigerianinfopedia.com.ng/chemistry-lesson-note-for-ss2-second-term/
• https://www.studygreen.com.ng/ss2-chemistry-third-term-lesson-note/

Instructional Materials

The teacher will teach this lesson with the aid of:

• Samples of electrovalent compounds (e.g., NaCl, CuSO4)
• Samples of covalent compounds (e.g., sugar, ethanol)
• Apparatus for testing conductivity (beakers, electrodes, battery, bulb)
• Samples of strong electrolytes (e.g., HCl, NaOH solution)
• Samples of weak electrolytes (e.g., ethanoic acid, ammonium hydroxide solution)
• Chart showing the electrochemical series.

Rationale for the Lesson

This lesson helps pupils understand how substances conduct electricity in solution and how ions behave. It enables them to predict chemical reactions involving ions, which is important for everyday applications like batteries and corrosion prevention.

Prerequisite/Previous Knowledge

Pupils have prior knowledge of atoms, molecules, chemical bonding (ionic and covalent), and basic concepts of electricity.

Lesson Content/Board Summary

IONIC THEORY

Meaning of Ionic Theory

Ionic theory states that certain substances, when dissolved in water or melted, dissociate into positively and negatively charged particles called ions. These ions are responsible for conducting electricity through the solution or melt.

Electrovalent (Ionic) and Covalent Compounds

Electrovalent Compounds: These are compounds formed by the complete transfer of electrons between atoms, resulting in the formation of ions held together by strong electrostatic forces. They are typically formed between metals and non-metals.

Covalent Compounds: These are compounds formed by the sharing of electrons between atoms. They usually consist of non-metals.

The following are key differences:

• Bonding: Electrovalent compounds have ionic bonds (electron transfer), while covalent compounds have covalent bonds (electron sharing).
• State at Room Temperature: Electrovalent compounds are usually solids with high melting and boiling points, while covalent compounds can be solids, liquids, or gases with lower melting and boiling points.
• Conductivity: Electrovalent compounds conduct electricity when molten or in solution (due to free ions), while covalent compounds generally do not conduct electricity.

Electrolytes and Non-electrolytes

Electrolytes: These are substances that conduct electricity when molten or dissolved in a suitable solvent, due to the presence of mobile ions. Examples include acids, bases, and salts.

Non-electrolytes: These are substances that do not conduct electricity in molten state or in solution because they do not produce mobile ions. Examples include sugar solution, ethanol, and tetrachloromethane.

Strong and Weak Electrolytes

Strong Electrolytes: These are electrolytes that dissociate completely or almost completely into ions when dissolved in a solvent, leading to high electrical conductivity. Examples include strong acids (HCl, H2SO4), strong bases (NaOH, KOH), and most salts (NaCl, CuSO4).

Weak Electrolytes: These are electrolytes that dissociate only partially into ions when dissolved in a solvent, resulting in low electrical conductivity. Examples include weak acids (CH3COOH, H2CO3) and weak bases (NH4OH).

Electrochemical Series (Reactivity Series of Ions)

The electrochemical series is a list of elements arranged in order of their increasing standard electrode potentials or decreasing ease of discharge at an electrode. It helps predict which ion will be preferentially discharged at an electrode during electrolysis.

Cations (Positive Ions): K+, Na+, Ca2+, Mg2+, Al3+, Zn2+, Fe2+, Pb2+, H+, Cu2+, Ag+, Au3+

Anions (Negative Ions): SO42-, NO3-, Cl-, Br-, I-, OH-

In general, for cations, ions lower in the series (more positive electrode potential) are more easily discharged. For anions, ions higher in the series (less negative electrode potential) are more easily discharged, except for hydroxide and halide ions.

Factors Affecting Preferential Discharge of Ions

During electrolysis, if more than one type of ion is present at an electrode, only one will be discharged preferentially. The factors determining this are:

• Position in the Electrochemical Series: Ions lower in the series (cations) or higher in the series (anions, excluding OH- and halides) are preferentially discharged.
• Concentration of Ions: If the difference in position in the series is small, a higher concentration of an ion can lead to its preferential discharge, even if it is slightly higher (for cations) or lower (for anions) in the series. For example, in concentrated NaCl solution, Cl- is discharged over OH-, but in dilute NaCl solution, OH- is discharged.
• Nature of the Electrode: Some electrodes (e.g., mercury cathode) can affect the discharge potential of certain ions, making them harder or easier to discharge. This is common in industrial processes.

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 recall what they know about chemical bonding and how some substances conduct electricity.
Pupils’ Activity: Pupils respond to the questions, recalling concepts of ionic and covalent bonding and conductivity.
Learning Point: Pupils connect previous knowledge to the new topic.

Step 2: Meaning of Ionic Theory

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher explains the concept of ionic theory, defining ions and their role in electrical conductivity in solutions or molten states.
Pupils’ Activity: Pupils listen attentively and ask questions for clarification.
Learning Point: Pupils understand that ions enable electrical conductivity in certain substances.

Step 3: Electrovalent/Covalent Compounds and Electrolytes/Non-electrolytes

Time: 10 minutes
Teaching Skill: Demonstration/Classification
Teacher’s Activity: The teacher guides pupils to distinguish between electrovalent and covalent compounds, providing examples. The teacher then demonstrates with simple apparatus how to test for electrolytes and non-electrolytes using samples like salt solution, sugar solution, and pure water.
Pupils’ Activity: Pupils observe the demonstration, classify the compounds, and identify which substances conduct electricity.
Learning Point: Pupils can differentiate between electrovalent and covalent compounds, and classify substances as electrolytes or non-electrolytes.

Step 4: Strong and Weak Electrolytes

Time: 5 minutes
Teaching Skill: Explanation/Comparison
Teacher’s Activity: The teacher explains the difference between strong and weak electrolytes, using examples like strong acids/bases/salts versus weak acids/bases. The teacher can show a simple demonstration of the difference in brightness of a bulb when testing strong vs. weak electrolytes.
Pupils’ Activity: Pupils observe the demonstration, compare the level of conductivity, and understand the concept of complete vs. partial dissociation.
Learning Point: Pupils can compare strong and weak electrolytes based on their degree of dissociation and conductivity.

Step 5: Electrochemical Series

Time: 5 minutes
Teaching Skill: Lecture/Visual Aid
Teacher’s Activity: The teacher introduces the electrochemical series, explaining its arrangement and importance in predicting the discharge of ions, using a chart.
Pupils’ Activity: Pupils observe the chart, copy the series, and understand its purpose.
Learning Point: Pupils learn about the electrochemical series and its use in predicting ion discharge.

Step 6: Factors Affecting Preferential Discharge of Ions

Time: 5 minutes
Teaching Skill: Discussion/Explanation
Teacher’s Activity: The teacher guides a discussion on the factors that affect the preferential discharge of ions during electrolysis, such as position in the series, concentration, and nature of the electrode.
Pupils’ Activity: Pupils participate in the discussion, ask questions, and note down the factors.
Learning Point: Pupils identify and explain the factors influencing the preferential discharge of ions.

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 ionic theory.
2. State two differences between electrovalent and covalent compounds.
3. Give two examples each of strong and weak electrolytes.
4. List three factors that affect the preferential discharge of ions during electrolysis.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, emphasizing the importance of ions in various chemical processes and everyday life. The teacher then gives pupils homework to research practical applications of electrolysis.
Pupils’ Activity: Pupils listen to the summary and copy down the homework assignment.
Learning Point: Pupils consolidate their understanding and recognize the relevance of the topic.

Lesson Keywords

• Ionic Theory – The explanation of how substances conduct electricity through mobile ions in solution or molten state.
• Ions – Electrically charged atoms or groups of atoms (cations are positive, anions are negative).
• Electrolyte – A substance that conducts electricity when molten or dissolved in a solvent due to the presence of mobile ions.
• Non-electrolyte – A substance that does not conduct electricity in molten state or solution.
• Electrovalent Compound – A compound formed by the transfer of electrons, resulting in ionic bonds.
• Covalent Compound – A compound formed by the sharing of electrons, resulting in covalent bonds.
• Electrochemical Series – A list of elements/ions arranged in order of their ease of discharge at an electrode.
• Preferential Discharge – The selective discharge of one ion over another at an electrode during electrolysis.

Differentiation

The teacher will provide additional examples and simplified explanations for pupils who are struggling, while encouraging advanced learners to explore more complex examples and applications of ionic theory.

Note for teachers using this lesson plan

Teachers should ensure all safety precautions are taken during demonstrations involving electricity and chemicals. Encourage active pupil participation through questions and practical activities.