Class: Senior Secondary School 2 (SS2 / SSS2)
Term: Second Term
Week: 3
Age: 16 years
Duration: 45 minutes
Subject: Chemistry
Curriculum Theme: Environmental Chemistry
Previous Lesson: Water: Hardness, Purification and Municipal Supply.
Topic: AIR
Subject Matter: Meaning of air (mixture of gases in the atmosphere), air constituents, percentage composition of air, properties of air, flame (zones of flame)

Specific Objectives

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

Cognitive Domain:

Define air as a mixture of gases.
List the major constituents of air and their approximate percentage compositions.
State at least three physical properties of air.
Identify and describe the different zones of a Bunsen burner flame.

Affective Domain:

Appreciate the importance of air for life and various industrial processes.
Show interest in observing experiments demonstrating the composition and properties of air.

Psychomotor Domain:

Draw and label the zones of a non-luminous Bunsen burner flame correctly.
Participate in simple demonstrations showing properties of air.

Collaborate with peers during group discussions or observation of experiments.

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:

Bunsen burner
Source of gas
Match stick or match box
Candle stick
Magnesium ribbon
Alkaline pyrogallol
Gas jar or measuring cylinder
Trough of water
Charts showing the composition of air and zones of flame

Rationale for the Lesson

This lesson enables pupils to understand the nature and composition of the air they breathe, which is essential for all living organisms. Knowledge of air’s properties and the characteristics of flames helps explain various natural phenomena and industrial applications.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of mixtures, elements, compounds, and states of matter from their previous chemistry lessons.

Lesson Content/Board Summary

AIR

Meaning of Air

Air is a colorless, odorless, and tasteless mixture of gases that surrounds the Earth, forming its atmosphere. It is essential for the survival of most living organisms.

Constituents of Air and Percentage Composition

Air is a mixture of several gases, with the major constituents being:

Nitrogen (N₂) – Approximately 78%
Oxygen (O₂) – Approximately 21%
Argon (Ar) – Approximately 0.9%
Carbon Dioxide (CO₂) – Approximately 0.03%
Other Noble Gases (Neon, Helium, Krypton, Xenon) – Trace amounts
Water Vapour – Variable amounts
Dust Particles – Variable amounts

Properties of Air

The following are some physical properties of air:

Air is a mixture, not a compound.
Air is colorless, odorless, and tasteless.
Air is invisible.
Air has mass and takes up space.
Air exerts pressure.
Air supports combustion (due to oxygen).
Air is a poor conductor of heat.

Flame (Zones of Flame)

A flame is the visible, gaseous part of a fire. It is produced when a combustible gas burns. Examples include a candle flame or a Bunsen burner flame.

Types of Flames:

Luminous Flame: Produced when there is an insufficient supply of air (oxygen). It is yellow, smoky, and deposits soot due to incomplete combustion of carbon particles.
Non-luminous Flame: Produced when there is a sufficient supply of air (oxygen). It is blue, steady, and clean, indicating complete combustion. This is the flame typically produced by a Bunsen burner with the air hole open.

Zones of a Non-Luminous Bunsen Burner Flame:

A non-luminous flame has distinct zones due to varying temperatures and combustion conditions:

Outer Zone (Non-luminous Zone / Zone of Complete Combustion):
- This is the hottest part of the flame (around 1500°C).
- It is pale blue and complete combustion occurs here due to ample oxygen.
Middle Zone (Luminous Zone / Zone of Incomplete Combustion):
- This zone is greenish-blue and less hot than the outer zone.
- Partial combustion of the gas occurs here, producing carbon monoxide.
Inner Zone (Dark Zone / Unburnt Gas Zone):
- This is the coolest part of the flame.
- It consists of unburnt gas and is dark in appearance. No combustion occurs here.

Note: Pupils should be able to draw and label a diagram showing these three zones of a non-luminous flame.

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 what they think air is made of and why it is important.
Pupils’ Activity: Pupils respond to the questions, sharing their prior knowledge about air.
Learning Point: Pupils recall previous knowledge and are introduced to the topic of air.

Step 2: Meaning and Composition of Air

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines air as a mixture of gases and explains its major constituents and their approximate percentages, demonstrating the presence of oxygen using a burning candle in an inverted gas jar over water or using alkaline pyrogallol with magnesium ribbon.
Pupils’ Activity: Pupils observe the demonstrations, listen attentively, and note down the definition and composition of air.
Learning Point: Pupils understand air as a mixture and identify its main components.

Step 3: Properties of Air

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher discusses and demonstrates some properties of air, such as its invisibility, mass, and ability to exert pressure, using simple experiments (e.g., weighing an inflated and deflated balloon, or using an inverted glass in water).
Pupils’ Activity: Pupils observe the demonstrations, participate in discussions, and record the properties of air.
Learning Point: Pupils identify and understand the physical properties of air.

Step 4: Flame and its Zones

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher lights a Bunsen burner, explains the difference between luminous and non-luminous flames, and identifies the three main zones of a non-luminous flame, highlighting their characteristics and temperatures.
Pupils’ Activity: Pupils carefully observe the Bunsen burner flame and listen to the explanation of the different zones.
Learning Point: Pupils learn about different types of flames and the distinct zones within a non-luminous flame.

Step 5: Drawing and Labelling Flame

Time: 5 minutes
Teaching Skill: Guidance/Visualisation
Teacher’s Activity: The teacher guides pupils on how to draw and label the three zones of a non-luminous Bunsen burner flame, emphasizing accuracy in labeling.
Pupils’ Activity: Pupils draw and label the zones of the Bunsen burner flame in their notebooks.
Learning Point: Pupils develop the skill to accurately represent the structure of a flame diagrammatically.

Step 6: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

Define air.
List three major gases in air and their approximate percentages.
State three physical properties of air.
Draw and label the three zones of a non-luminous Bunsen burner flame.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 7: Conclusion

Time: 2 minutes
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of air and its components, and the structure of a flame.
Pupils’ Activity: Pupils listen to the summary and ask any remaining questions.
Learning Point: Pupils reinforce their understanding of the topic.

Step 8: Assignment

Time: 3 minutes
Teacher’s Activity: The teacher gives the following assignment: “Research and write down two industrial uses of oxygen and two of nitrogen.”
Pupils’ Activity: Pupils copy the assignment into their notebooks.
Learning Point: Pupils engage in further independent study related to the lesson.

Lesson Keywords

Air – The mixture of gases surrounding the Earth.
Mixture – A substance containing two or more substances not chemically combined.
Nitrogen – The most abundant gas in the atmosphere (approx. 78%).
Oxygen – A gas essential for respiration and combustion (approx. 21%).
Carbon Dioxide – A gas produced by respiration and combustion, used by plants for photosynthesis.
Flame – The visible, gaseous part of a fire.
Luminous Flame – A yellow, sooty flame due to incomplete combustion.
Non-luminous Flame – A blue, clean flame due to complete combustion.
Zones of Flame – Distinct regions within a flame with different temperatures and combustion conditions.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to explain the chemical reactions occurring in each zone of the flame. For those who need more support, the teacher will provide simplified diagrams and allow for peer tutoring during the drawing activity.

Note for teachers using this lesson plan

Ensure all demonstration materials are ready before the lesson. Emphasize safety precautions when using the Bunsen burner. Encourage pupils to actively participate in observations and discussions. Use charts to visually represent the composition of air and the zones of the flame for better understanding.