Class: Senior Secondary School 2 (SS2 / SSS2)
Term: Second Term
Week: 5
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Chemical Reactions
Previous Lesson: Hydrogen: Meaning, Configuration, Preparation and Uses.
Topic: OXYGEN
Subject Matter: Meaning of oxygen, general properties of oxygen group, electronic structure and bonding capacity of oxygen, laboratory and industrial preparation of oxygen, physical and chemical properties of oxygen, reaction of oxygen (oxidation), compounds of oxygen, uses of oxygen.

Specific Objectives

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

Cognitive Domain:

Define oxygen as a reactive non-metal gas.
State the general properties of the oxygen group (Group 16).
Outline the laboratory and industrial preparation methods of oxygen.
Describe the physical and chemical properties of oxygen.
Explain the concept of oxidation and give examples.
List various uses of oxygen.

Affective Domain:

Appreciate the importance of oxygen in daily life and industrial processes.
Demonstrate interest in observing chemical demonstrations.
Recognize the safety precautions during laboratory experiments involving gases.

Psychomotor Domain:

Draw the electronic configuration of oxygen.
Observe the laboratory preparation of oxygen and the glowing splint test.
Write balanced chemical equations for oxygen preparation and reactions.

Discuss the applications of oxygen in various sectors.
Collaborate with peers in understanding oxygen’s properties and uses.

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:

Periodic table
Picture showing a welder at work
Laboratory apparatus for preparation of oxygen (test tubes, delivery tubes, gas jar, trough, retort stand)
Reagents for preparation of oxygen (hydrogen peroxide, manganese (IV) oxide)
Matches
Splint

Rationale for the Lesson

Understanding oxygen is important because it is an essential gas for life and plays a significant role in many industrial processes. This lesson helps pupils grasp its properties, preparation, and applications, which are fundamental to chemistry and daily existence.

Prerequisite/Previous Knowledge

Pupils are expected to have basic knowledge of elements, atomic structure, the periodic table, and simple chemical reactions from previous lessons.

Lesson Content/Board Summary

Oxygen

Meaning of Oxygen

Oxygen is a highly reactive non-metal gas found in Group 16 of the periodic table. It is essential for the respiration of living organisms and supports combustion.

General Properties of Oxygen Group (Group 16 / VIA)

The elements in Group 16 include Oxygen (O), Sulphur (S), Selenium (Se), Tellurium (Te), and Polonium (Po). They are often called chalcogens. Key properties include:

They are generally non-metals, with metallic character increasing down the group.
They typically exhibit a valency of -2 in compounds.
They are highly electronegative, with oxygen being the second most electronegative element.

Electronic Structure and Bonding Capacity of Oxygen

Oxygen has an atomic number of 8.

Electronic Configuration: 1s² 2s² 2p⁴
Valence Electrons: 6
Bonding Capacity: Oxygen typically forms two covalent bonds to achieve a stable octet, or forms an oxide ion (O²⁻) by gaining two electrons.

Laboratory Preparation of Oxygen

Oxygen can be prepared in the laboratory by the catalytic decomposition of hydrogen peroxide.

Method: Hydrogen peroxide (H₂O₂) is decomposed using manganese (IV) oxide (MnO₂) as a catalyst. The gas is collected over water due to its slight solubility.

Equation: 2H₂O₂(aq) –(MnO₂)–> 2H₂O(l) + O₂(g)

Test for Oxygen: Oxygen rekindles a glowing splint.

Industrial Preparation of Oxygen

Oxygen is prepared industrially by the fractional distillation of liquid air. Air is first liquefied by cooling and compression, then slowly warmed. Nitrogen (boiling point -196°C) distills off first, followed by argon (boiling point -186°C), and then oxygen (boiling point -183°C) is collected.

Physical Properties of Oxygen

Colourless gas
Odourless gas
Tasteless gas
Slightly soluble in water
Denser than air
Liquefies at -183°C to a pale blue liquid

Chemical Properties of Oxygen

Supports Combustion: Oxygen does not burn itself but supports the burning of other substances. Many substances burn more vigorously in pure oxygen than in air.
Reaction with Metals: Reacts with most metals to form metal oxides (e.g., magnesium burns in oxygen to form magnesium oxide).
2Mg(s) + O₂(g) → 2MgO(s)
Reaction with Non-metals: Reacts with many non-metals to form non-metal oxides (e.g., carbon burns in oxygen to form carbon dioxide).
C(s) + O₂(g) → CO₂(g)
Oxidation: Oxygen is a strong oxidizing agent.

Oxidation

Oxidation is a chemical process that involves the addition of oxygen to a substance, the removal of hydrogen, the loss of electrons, or an increase in oxidation number.

Examples:

Rusting of iron (slow oxidation): 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)
Burning of methane: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)

Compounds of Oxygen

Oxygen forms various compounds, primarily oxides. Oxides can be classified as:

Acidic Oxides: Formed by non-metals, react with water to form acids (e.g., CO₂, SO₃).
Basic Oxides: Formed by metals, react with water to form bases (e.g., Na₂O, CaO).
Amphoteric Oxides: React with both acids and bases (e.g., Al₂O₃, ZnO).
Neutral Oxides: Do not react with acids or bases (e.g., CO, N₂O).
Peroxides: Contain the O₂²⁻ ion (e.g., H₂O₂, Na₂O₂).

Uses of Oxygen

Respiration: Essential for breathing in living organisms.
Welding and Cutting: Used in oxy-acetylene flames for welding and cutting metals (e.g., by welders).
Medical Purposes: Used in hospitals for patients with breathing difficulties.
Steel Production: Used to remove impurities from molten iron to produce steel.
Rocket Fuel: Liquid oxygen is used as an oxidizer in rocket propulsion.
Water Treatment: Used in some water purification 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 name some elements they know. The teacher then asks about the gases present in the air and guides them to identify oxygen as one of the most important gases.
Pupils’ Activity: Pupils respond by naming elements and gases. They identify oxygen as a vital gas in the air.
Learning Point: Pupils are introduced to the topic of oxygen and its general importance.

Step 2: General Properties of Oxygen Group

Time: 7 minutes
Teaching Skill: Explanation/Discussion
Teacher’s Activity: The teacher uses the periodic table to explain the position of oxygen and highlights the general properties of Group 16 elements, such as their non-metallic nature and valency.
Pupils’ Activity: Pupils observe the periodic table and listen attentively, asking questions for clarification.
Learning Point: Pupils understand oxygen’s position in the periodic table and the general characteristics of its group.

Step 3: Electronic Structure and Bonding Capacity

Time: 7 minutes
Teaching Skill: Guided Practice
Teacher’s Activity: The teacher guides pupils to determine the atomic number and electronic configuration of oxygen. The teacher then explains how this configuration relates to its bonding capacity.
Pupils’ Activity: Pupils write down the electronic configuration and draw the electron shell diagram of oxygen.
Learning Point: Pupils learn about the atomic structure and bonding behavior of oxygen.

Step 4: Laboratory Preparation and Test for Oxygen

Time: 8 minutes
Teaching Skill: Demonstration/Experimentation
Teacher’s Activity: The teacher sets up the apparatus for the laboratory preparation of oxygen using hydrogen peroxide and manganese (IV) oxide. The teacher then performs the experiment and demonstrates the glowing splint test for oxygen.
Pupils’ Activity: Pupils observe the demonstration carefully and note the procedure and the result of the test for oxygen.
Learning Point: Pupils learn the laboratory method of preparing oxygen and how to test for its presence.

Step 5: Physical and Chemical Properties

Time: 7 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains the physical properties of oxygen. The teacher then performs simple experiments or uses visuals to demonstrate chemical properties, such as combustion in oxygen.
Pupils’ Activity: Pupils observe the demonstrations and record the physical and chemical properties of oxygen.
Learning Point: Pupils understand the observable characteristics and reactive nature of oxygen.

Step 6: Oxidation, Compounds, and Uses of Oxygen

Time: 6 minutes
Teaching Skill: Explanation/Listing
Teacher’s Activity: The teacher explains the concept of oxidation with examples. The teacher also discusses various compounds of oxygen and highlights the diverse uses of oxygen, showing the picture of a welder.
Pupils’ Activity: Pupils listen, take notes, list examples of oxidation, types of oxygen compounds, and the uses of oxygen.
Learning Point: Pupils learn about oxidation, different oxygen compounds, and the practical applications of oxygen.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

Define oxygen.
State three physical properties of oxygen.
Describe the laboratory preparation of oxygen, including the balanced chemical equation.
How would you test for oxygen in the laboratory?
Mention four uses of oxygen.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 1 minute
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reinforcing the importance of oxygen.
Pupils’ Activity: Pupils listen and reflect on the lesson.
Learning Point: The lesson is brought to a logical close, consolidating learning.

Lesson Keywords

Oxygen – A colourless, odourless, tasteless gas essential for life and combustion.
Oxidation – A chemical process involving the addition of oxygen, removal of hydrogen, or loss of electrons.
Combustion – The process of burning, which requires oxygen.
Group 16 – The group in the periodic table where oxygen is located.
Catalyst – A substance that speeds up a chemical reaction without being consumed.

Differentiation

For pupils who grasp concepts quickly, the teacher can encourage them to research other industrial applications of oxygen or more complex oxidation reactions. For pupils needing more support, the teacher will provide simplified notes and more one-on-one guidance during the demonstration and question sessions.

Note for teachers using this lesson plan

Ensure all laboratory demonstrations are conducted safely with appropriate ventilation. Encourage pupils to actively participate in discussions and to observe experiments carefully. Emphasize the real-world relevance of oxygen to enhance engagement.