Alkaline Earth Metals and Their General Properties for SS 3

Class: SS 3
Term: First Term
Week: 2
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Metals and Their Compounds
Previous Lesson: Metals and Their Compounds, Properties and Extraction
Topic: METALS AND THEIR COMPOUNDS – extraction of calcium
Subject Matter: The alkali earth metals; (general properties); Calcium: properties of calcium, compounds of calcium, and uses of calcium; Aluminium: extraction of aluminium and uses of aluminium

Specific Objectives

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

Cognitive Domain

• State the general properties of alkaline earth metals.
• Describe the physical and chemical properties of calcium.
• Identify common compounds of calcium.
• Explain the uses of calcium and its compounds.
• Describe the extraction process of aluminium.
• List the uses of aluminium.

Affective Domain

• Appreciate the importance of alkaline earth metals and aluminium in daily life and industries.
• Show interest in learning about the properties and applications of different metals.

Psychomotor Domain

• Illustrate the general properties of alkaline earth metals with examples.
• Outline the steps involved in the extraction of aluminium.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• A suitable Chemistry textbook for SS 3
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• A periodic table chart
• Charts showing the properties and uses of calcium and aluminium
• Diagrams illustrating the extraction of aluminium (Hall-Héroult process)
• List of mining and metal-related industries in Nigeria.

Rationale for the Lesson

This lesson provides students with a foundational understanding of alkaline earth metals and aluminium, which are crucial in various industrial and biological processes. Understanding their properties, compounds, and extraction methods helps students appreciate their significance in technology, construction, and everyday applications. This knowledge also forms a basis for further studies in inorganic chemistry and materials science.

Prerequisite/Previous Knowledge

Students should have a basic understanding of the periodic table, general properties of metals, and concepts of chemical bonding from their previous chemistry classes.

Lesson Content/Board Summary

METALS AND THEIR COMPOUNDS – extraction of calcium

Alkaline Earth Metals

General Properties

Alkaline earth metals are elements in Group 2 of the periodic table. They include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra).

1. They are reactive metals, though less reactive than alkali metals.
2. They have two valence electrons, which they readily lose to form +2 ions.
3. They are good reducing agents.
4. They are silvery-white, relatively soft, and have low densities, melting points, and boiling points compared to transition metals.
5. They react with water to form hydroxides and hydrogen gas (except beryllium and magnesium which react slowly with steam).
6. They form ionic compounds with non-metals.

Calcium

Properties of Calcium

Calcium is a reactive silvery-white metal that is relatively soft and ductile.

Physical Properties:

1. Silvery-white and relatively soft.
2. Good conductor of heat and electricity.
3. Melting point: 842 °C.
4. Boiling point: 1484 °C.
5. Density: 1.55 g/cm³.

Chemical Properties:

1. Reacts with oxygen to form calcium oxide (CaO).
2. Reacts with water to form calcium hydroxide (Ca(OH)₂) and hydrogen gas.
3. Reacts with dilute acids to produce hydrogen gas and a calcium salt.
4. Burns with a brick-red flame.

Compounds of Calcium

Some important compounds of calcium include:

1. Calcium Carbonate (CaCO₃): Found naturally as limestone, marble, and chalk. Used in cement production, as an antacid, and in agriculture.
2. Calcium Oxide (CaO) or Quicklime: Produced by heating calcium carbonate. Used in steel making, water treatment, and as a refractory material.
3. Calcium Hydroxide (Ca(OH)₂) or Slaked Lime: Formed by adding water to quicklime. Used to neutralize acidic soils, in mortar, and as a flocculant in water purification.
4. Calcium Sulphate (CaSO₄) or Gypsum: Used in plaster of Paris, cement, and as a fertilizer.

Uses of Calcium

Calcium and its compounds have numerous applications:

1. Construction: Calcium carbonate (limestone) is a primary raw material for cement and concrete. Calcium hydroxide is used in mortar.
2. Agriculture: Calcium compounds are used to neutralize acidic soils and as plant nutrients.
3. Metallurgy: Used as a reducing agent in the extraction of some metals.
4. Food Industry: Calcium supplements are used for bone health. Calcium chloride is used as a firming agent in canned vegetables.
5. Water Treatment: Calcium hydroxide is used to remove impurities from water.

Aluminium

Extraction of Aluminium

Aluminium is extracted from its ore, bauxite (Al₂O₃.nH₂O), using the Hall-Héroult process, which involves two main stages:

Stage 1: Purification of Bauxite (Bayer Process)

1. Bauxite is crushed and heated with concentrated sodium hydroxide solution under pressure. Aluminium oxide dissolves to form sodium aluminate (NaAlO₂), while impurities like iron oxides remain undissolved.
2. The solution is filtered to remove impurities.
3. The filtrate is cooled and diluted, then seeded with aluminium hydroxide crystals. Aluminium hydroxide precipitates out.
4. The aluminium hydroxide is filtered, washed, and then heated strongly (calcined) to obtain pure anhydrous aluminium oxide (alumina, Al₂O₃).

Stage 2: Electrolytic Reduction (Hall-Héroult Process)

1. Pure alumina is dissolved in molten cryolite (Na₃AlF₆) at about 950 °C in a large steel tank lined with carbon (cathode).
2. Carbon rods serve as anodes, dipped into the molten mixture.
3. When electric current is passed through, aluminium ions (Al³⁺) migrate to the cathode, gain electrons, and are reduced to molten aluminium.
4. Oxygen ions (O²⁻) migrate to the anode, lose electrons, and react with the carbon anodes to form carbon dioxide. This causes the anodes to be consumed and requires regular replacement.
5. Molten aluminium, being denser, collects at the bottom of the cell and is tapped off.

Uses of Aluminium

Aluminium is a versatile metal with many applications due to its properties:

1. Aircraft and Automotive Industries: Its low density and high strength-to-weight ratio make it ideal for aircraft bodies, car parts, and bicycles.
2. Construction: Used in window frames, roofing, and structural components due to its light weight and corrosion resistance.
3. Packaging: Used for beverage cans, foil wraps, and food containers because it is non-toxic, lightweight, and recyclable.
4. Electrical Conductivity: Used in electrical transmission lines, though less conductive than copper, it is lighter and cheaper.
5. Cooking Utensils: Used for pots and pans due to its good thermal conductivity.
6. Alloys: Forms strong alloys with other metals (e.g., duralumin with copper and magnesium) for various engineering applications.

Teaching Methods/Instructional Techniques

Discussion, Explanation, Question and Answer, Demonstration, Guided Practice

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Recalling/Engaging

Teacher’s Activity: The teacher greets the students and asks questions to review their prior knowledge on metals, specifically asking them to classify metals into groups from the periodic table.

Pupils’ Activity: Students respond to questions, recalling the concept of metals and their classification.

Learning Point: Metals classification review

Step 2: General Properties of Alkaline Earth Metals

Time: 10 minutes

Teaching Skill: Explaining/Illustrating

Teacher’s Activity: The teacher introduces alkaline earth metals (Group 2) and explains their general physical and chemical properties, using the periodic table chart. The teacher highlights their reactivity and tendency to form +2 ions.

Pupils’ Activity: Students listen, observe the periodic table, and ask questions for clarification on the properties.

Learning Point: Alkaline earth properties

Step 3: Properties of Calcium

Time: 7 minutes

Teaching Skill: Describing/Detailing

Teacher’s Activity: The teacher focuses on calcium, describing its specific physical properties (e.g., colour, density, conductivity) and chemical properties (e.g., reaction with oxygen, water, acids).

Pupils’ Activity: Students pay attention and note down the key properties of calcium.

Learning Point: Calcium’s physical properties

Step 4: Compounds of Calcium

Time: 5 minutes

Teaching Skill: Listing/Identifying

Teacher’s Activity: The teacher lists and briefly explains common compounds of calcium such as calcium carbonate, calcium oxide, calcium hydroxide, and calcium sulphate, mentioning their common names.

Pupils’ Activity: Students listen and identify the common compounds of calcium.

Learning Point: Common calcium compounds

Step 5: Uses of Calcium

Time: 3 minutes

Teaching Skill: Discussing/Applying

Teacher’s Activity: The teacher discusses the various uses of calcium and its compounds in construction, agriculture, food, and water treatment, relating them to everyday life.

Pupils’ Activity: Students contribute examples of calcium uses they know and relate them to the discussion.

Learning Point: Practical uses of calcium

Step 6: Extraction and Uses of Aluminium

Time: 5 minutes

Teaching Skill: Explaining/Summarising

Teacher’s Activity: The teacher explains the Hall-Héroult process for aluminium extraction, simplifying the two main stages (Bayer and electrolytic reduction). The teacher then lists the key uses of aluminium, highlighting its desirable properties.

Pupils’ Activity: Students listen attentively and ask questions about the extraction process and uses.

Learning Point: Aluminium extraction process

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 general properties of alkaline earth metals.
2. State two physical and two chemical properties of calcium.
3. Name two common compounds of calcium and their uses.
4. Briefly describe the main steps in the extraction of aluminium.
5. Mention three uses of aluminium.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Alkaline earth metal knowledge

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 alkaline earth metals, calcium, and aluminium into their notebooks.

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

Learning Point: Board notes copying

Step 9: Conclusion

Time: 1 minute

Teaching Skill: Summarising

Teacher’s Activity: The teacher briefly reminds students about the significance of alkaline earth metals and aluminium in various industries and daily life, encouraging them to observe these applications around them.

Pupils’ Activity: Students listen and reflect on the lesson’s main points.

Learning Point: Lesson concept reinforcement

Continuous Assessment/Further Study

Type: Homework

Instruction: Answer the following questions in your notebook:

1. Compare the reactivity of alkaline earth metals with alkali metals, giving reasons for the difference.
2. Research and write a short paragraph on the environmental impact of bauxite mining and aluminium production.
3. Identify five products in your home that contain aluminium and explain why aluminium is suitable for those products.

Lesson Keywords

• Alkaline Earth Metals – Elements in Group 2 of the periodic table, including calcium and magnesium.
• Calcium – A reactive silvery-white alkaline earth metal.
• Aluminium – A lightweight, corrosion-resistant metal extracted from bauxite.
• Bauxite – The primary ore from which aluminium is extracted.
• Cryolite – A molten salt (Na₃AlF₆) used as a solvent for alumina in aluminium extraction.
• Hall-Héroult Process – The electrolytic process used to extract aluminium from alumina.
• Quicklime (CaO) – Calcium oxide, formed by heating calcium carbonate.
• Slaked Lime (Ca(OH)₂) – Calcium hydroxide, formed by adding water to quicklime.

Differentiation

For weaker learners, the teacher can provide simplified diagrams of the aluminium extraction process and a handout summarising the properties. Faster learners can be challenged to research other important alkaline earth metals like magnesium and strontium, and their industrial uses, or to explain the chemical reactions involved in calcium’s properties in more detail.

Suggested Lesson Videos

For further understanding, students can search on YouTube for:

• “General properties of alkaline earth metals”
• “Extraction of aluminium Hall-Héroult process”
• “Uses of calcium and aluminium”

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have a clear periodic table and any charts or diagrams related to calcium and aluminium properties and extraction. Begin by reviewing basic metal concepts to activate prior knowledge. Present the general properties of alkaline earth metals clearly, then focus on calcium’s specific properties, compounds, and uses, linking them to real-world examples. When explaining aluminium extraction, simplify the Hall-Héroult process into its key stages (purification and electrolysis) rather than overwhelming students with excessive detail. Encourage students to ask questions throughout the lesson. After the main teaching points, conduct the evaluation questions orally and in writing to check understanding. Guide students to copy the Board Summary notes, ensuring they capture the essential information. For safety, remind students that these are laboratory concepts and direct handling of reactive metals should only be done under strict supervision.