Metals and Their Compounds, Properties and Extraction for SS 3

Class: SS 3
Term: First Term
Week: 1
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Chemical Reactions and Stoichiometry
Previous Lesson:
Topic: METALS AND THEIR COMPOUNDS
Subject Matter: Metals: chemical characteristics and relative abundance; Compounds of metals; Principles of extraction of metals: electrolysis, reduction of oxides, reduction of chlorides, and reduction of sulphates; The alkali metal (General properties); Sodium: extraction of sodium, properties of sodium, and uses of sodium

Specific Objectives

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

Cognitive Domain

• State the general chemical characteristics of metals.
• Identify the relative abundance of common metals in nature.
• Explain the principles of metal extraction by electrolysis.
• Describe the principles of metal extraction by reduction of oxides.
• Outline the principles of metal extraction by reduction of chlorides.
• Explain the principles of metal extraction by reduction of sulphates.
• List the general properties of alkali metals.
• Describe the extraction process of sodium.
• State the physical and chemical properties of sodium.
• Identify various uses of sodium.

Affective Domain

• Appreciate the importance of metals in everyday life.
• Show interest in learning about the industrial processes of metal extraction.

Psychomotor Domain

• Locate metals on the periodic table.
• Draw simple diagrams illustrating metal extraction processes.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Essential Chemistry for Senior Secondary Schools by O. A. Ojokuku
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Samples of metals (e.g., iron filings, aluminium foil, copper wire) and some of their compounds (e.g., iron oxide, sodium chloride).
• A large periodic table of elements chart.
• Charts showing mineral ore distribution in Nigeria (e.g., tin, iron ore).
• Diagrams illustrating the Down’s process for sodium extraction and blast furnace for iron extraction.

Rationale for the Lesson

This lesson is important as it provides students with a foundational understanding of metals, which are essential materials in technology, industry, and daily life. It explains how these valuable resources are obtained from their ores, linking theoretical chemistry to practical industrial applications. Understanding metal extraction is crucial for appreciating Nigeria’s mineral wealth and industrial development.

Prerequisite/Previous Knowledge

Students should have prior knowledge of the periodic table, basic chemical bonding, oxidation and reduction reactions, and the general classification of elements into metals and non-metals from JSS 3 and SS 1 chemistry.

Lesson Content/Board Summary

METALS AND THEIR COMPOUNDS

Chemical Characteristics and Relative Abundance of Metals

Metals are elements that typically:

1. Are electropositive, readily losing electrons to form positive ions (cations).
2. Are good conductors of heat and electricity.
3. Are malleable (can be hammered into sheets) and ductile (can be drawn into wires).
4. Have high melting and boiling points (generally).
5. Are lustrous (shiny).
6. Form basic oxides and hydroxides.
7. Act as reducing agents in chemical reactions.

Relative abundance refers to how commonly metals are found in the Earth’s crust. Common abundant metals include:

1. Aluminium (most abundant metal)
2. Iron
3. Calcium
4. Sodium
5. Potassium

In Nigeria, significant deposits of metals like tin and iron are found as minerals.

Compounds of Metals

Metals readily form compounds by reacting with non-metals (e.g., oxygen, chlorine, sulphur) to form ionic compounds. Examples include:

1. Oxides (e.g., Fe₂O₃, Al₂O₃, Na₂O)
2. Chlorides (e.g., NaCl, FeCl₃)
3. Sulphates (e.g., CuSO₄, FeSO₄)
4. Carbonates (e.g., CaCO₃)

These compounds often serve as the ores from which metals are extracted.

Principles of Extraction of Metals

The method of extraction depends on the metal’s reactivity and the nature of its ore.

1. Electrolysis

   This method is used for highly reactive metals (e.g., sodium, potassium, calcium, magnesium, aluminium) that cannot be easily reduced by chemical reducing agents. It involves passing an electric current through the molten ore (usually a chloride or oxide) or an aqueous solution of its salt.

   Example: Extraction of sodium from molten sodium chloride (Down’s process).

2. Reduction of Oxides

   This is common for moderately reactive metals (e.g., iron, zinc, lead, tin). The metal oxide ore is heated with a suitable reducing agent like carbon (coke), carbon monoxide, or hydrogen.

   Example: Extraction of iron in a blast furnace where iron(III) oxide is reduced by carbon monoxide.

   (text{Fe}_2text{O}_3(s) + 3text{CO}(g) xrightarrow{text{heat}} 2text{Fe}(s) + 3text{CO}_2(g))

3. Reduction of Chlorides

   While some chlorides are electrolysed, direct chemical reduction of metal chlorides is less common but can occur. For instance, some less reactive metal chlorides can be reduced by more reactive metals or hydrogen at high temperatures.

   Example: Reduction of titanium(IV) chloride by magnesium (Kroll process) to produce titanium metal.

   (text{TiCl}_4(g) + 2text{Mg}(l) xrightarrow{text{heat}} text{Ti}(s) + 2text{MgCl}_2(l))

4. Reduction of Sulphates

   Direct reduction of metal sulphates to the metal is generally not a primary industrial method. Sulphate ores are typically roasted first to convert them into oxides, which are then reduced. However, in some specific cases, sulphates can be thermally decomposed or reduced under controlled conditions.

   Example: Lead sulphate can be converted to lead oxide, which is then reduced.

The Alkali Metals (General Properties)

Alkali metals are Group 1 elements (Lithium, Sodium, Potassium, Rubidium, Caesium, Francium). They are characterized by:

1. Having one valence electron.
2. Being highly reactive, readily losing their single valence electron to form +1 ions.
3. Being soft, silvery-white metals with low densities.
4. Having low melting and boiling points.
5. Being strong reducing agents.
6. Reacting vigorously with water to produce hydrogen gas and a metal hydroxide.
7. Forming basic oxides and hydroxides.

Sodium

Sodium is a highly reactive alkali metal.

1. Extraction of Sodium

   Sodium is extracted commercially by the electrolysis of molten sodium chloride (NaCl) in the Down’s process. Calcium chloride (CaCl₂) is added to lower the melting point of NaCl from 801°C to about 600°C.

   At the cathode (negative electrode): (text{Na}^+(l) + text{e}^- rightarrow text{Na}(l))

   At the anode (positive electrode): (text{2Cl}^-(l) rightarrow text{Cl}_2(g) + 2text{e}^-)

   Overall reaction: (text{2NaCl}(l) xrightarrow{text{electrolysis}} 2text{Na}(l) + text{Cl}_2(g))

2. Properties of Sodium

   • Physical Properties:
   1. Silvery-white, soft metal.
   2. Low melting point (97.8°C).
   3. Low density (0.97 g/cm³), floats on water.
   4. Good conductor of heat and electricity.
3. Chemical Properties:
1. Highly reactive, stored under paraffin oil to prevent reaction with air/moisture.
2. Reacts vigorously with water to produce sodium hydroxide and hydrogen gas:
   (text{2Na}(s) + 2text{H}_2text{O}(l) rightarrow 2text{NaOH}(aq) + text{H}_2(g))
3. Burns in air with a yellow flame to form sodium oxide and some sodium peroxide.
4. Reacts with chlorine to form sodium chloride.

4. Uses of Sodium

   1. As a coolant in nuclear reactors (due to its high thermal conductivity).
   2. In sodium vapour lamps for street lighting (produces a bright yellow light).
   3. To produce Na/Pb alloy for the manufacture of tetraethyl lead (an anti-knock agent, though less common now).
   4. As a strong reducing agent in the extraction of certain metals (e.g., titanium).
   5. In the manufacture of sodium cyanide, sodium peroxide, and other sodium compounds.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Charts and Diagrams.

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Activating Prior Knowledge

Teacher’s Activity: The teacher greets the students and asks them to recall what they know about metals from previous classes, asking for examples and common properties. The teacher then introduces the lesson topic: “Metals and Their Compounds.”

Pupils’ Activity: Students respond to questions about metals and listen attentively to the introduction.

Learning Point: Metals and their properties

Step 2: Chemical Characteristics and Identification of Metals

Time: 8 minutes

Teaching Skill: Explanation/Demonstration

Teacher’s Activity: The teacher explains the general chemical characteristics of metals (electropositivity, conductivity, malleability, ductility, etc.) and demonstrates with samples where possible. The teacher then leads students to identify the metallic regions on the periodic table chart.

Pupils’ Activity: Students observe the samples, listen to explanations, and identify metals on the periodic table.

Learning Point: Metal characteristics and location

Step 3: Relative Abundance of Metals

Time: 5 minutes

Teaching Skill: Illustration/Discussion

Teacher’s Activity: The teacher shows charts illustrating the relative abundance of metals in nature, emphasizing the occurrence of important metallic minerals like tin and iron in Nigeria. The teacher discusses how this abundance influences economic activities.

Pupils’ Activity: Students observe the charts, participate in discussions, and note key information about metal abundance in Nigeria.

Learning Point: Metal abundance and occurrence

Step 4: Principles of Metal Extraction (Electrolysis and Oxide Reduction)

Time: 7 minutes

Teaching Skill: Explanation/Diagrammatic Illustration

Teacher’s Activity: The teacher explains the principles of metal extraction, starting with electrolysis for highly reactive metals and reduction of oxides for moderately reactive metals. The teacher uses diagrams (e.g., blast furnace for iron) to illustrate these processes, relating them to examples like tin-mining and iron and steel production in Nigeria.

Pupils’ Activity: Students listen, ask questions, and observe the diagrams, relating the principles to real-world examples.

Learning Point: Electrolysis and oxide reduction

Step 5: Principles of Metal Extraction (Chloride and Sulphate Reduction)

Time: 5 minutes

Teaching Skill: Explanation

Teacher’s Activity: The teacher continues by explaining the principles of metal extraction through the reduction of chlorides and sulphates, clarifying that these methods might be direct or involve intermediate steps like conversion to oxides. The teacher provides examples where applicable.

Pupils’ Activity: Students listen and understand the less common reduction methods for chlorides and sulphates.

Learning Point: Chloride and sulphate reduction

Step 6: Alkali Metals and Sodium

Time: 5 minutes

Teaching Skill: Explanation/Questioning

Teacher’s Activity: The teacher introduces the alkali metals, discussing their general properties. The teacher then focuses on sodium, explaining its extraction process (Down’s process) and its key physical and chemical properties, using diagrams to show the setup.

Pupils’ Activity: Students listen, answer questions about alkali metals, and learn about sodium’s extraction and properties.

Learning Point: Alkali metals and sodium

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. List three chemical characteristics of metals.
2. Name two metals found abundantly in Nigeria.
3. Explain the principle of extraction by electrolysis.
4. Describe two uses of sodium.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Metal properties and extraction

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on metals and their extraction into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Recording lesson notes

Step 9: Conclusion

Time: 1 minute

Teaching Skill: Summarization

Teacher’s Activity: The teacher briefly summarizes the lesson by reiterating the importance of metals and their extraction processes, encouraging students to continue exploring the topic.

Pupils’ Activity: Students listen and prepare for the next lesson.

Learning Point: Lesson summary

Continuous Assessment/Further Study

Type: Homework

Instruction: Answer the following questions in your notebook.

1. Compare and contrast the extraction of iron from its ore with the extraction of sodium.
2. Research and write a short paragraph on the environmental impact of metal mining and extraction in Nigeria, suggesting possible solutions.

Lesson Keywords

• Metals – Elements that readily lose electrons to form positive ions, typically good conductors.
• Extraction – The process of obtaining a metal from its ore.
• Electrolysis – Chemical decomposition by electric current, used for highly reactive metals.
• Reduction – A chemical reaction involving the gain of electrons or the loss of oxygen.
• Alkali Metals – Group 1 elements, highly reactive, with one valence electron.
• Sodium – A highly reactive alkali metal, silvery-white and soft.
• Down’s Process – The industrial method for extracting sodium by electrolysis of molten NaCl.

Differentiation

For weaker learners: Provide simplified diagrams and flowcharts for the extraction processes. Focus on identifying the main characteristics of metals and the primary extraction methods (electrolysis and oxide reduction). Encourage peer tutoring.

For faster learners: Challenge them to research other specific examples of metal extraction (e.g., aluminium, copper) or delve deeper into the chemical reactions involved in each process. Ask them to explain why certain metals are extracted by specific methods.

Suggested Lesson Videos

Search on YouTube for: “Metals chemical properties SS3 Chemistry”, “Extraction of metals principles”, “Downs process sodium extraction”

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure all instructional materials, especially the metal samples, periodic table, and charts of mineral distribution, are ready and easily accessible. Begin by engaging students with their existing knowledge of metals to build a foundation. When discussing extraction principles, use clear diagrams and relate them to local contexts like tin and iron mining in Nigeria to make the lesson more relevant. Emphasize the reactivity series as the basis for choosing extraction methods. Students should copy the Board Summary notes into their notebooks after the main teaching points have been covered and reviewed. Encourage questions throughout the lesson to check understanding and address misconceptions promptly. For weaker learners, simplify explanations and provide more visual aids. For faster learners, encourage independent research and deeper analysis of the concepts.