Class: Senior Secondary School 1 (SS1 / SSS1)
Term: 1st Term
Week: 7
Age: 15 years
Duration: 45 minutes
Subject: Machine Wood Work
Curriculum Theme: Technology
Previous Lesson: Properties Of Timber: Observing Physical Properties.
Topic: Properties of timber
Subject Matter: Differences between softwood and hardwood, Physical properties comparison, Common West African timbers

Specific Objectives

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

Cognitive Domain:

Define softwood and hardwood.
State three differences between softwood and hardwood.
List five physical properties of timber.
Identify three common West African timbers.

Affective Domain:

Appreciate the importance of knowing timber properties for selecting appropriate wood.
Develop an interest in identifying different timber types.

Psychomotor Domain:

Distinguish between samples of softwood and hardwood.
Handle timber samples carefully during observation.

Collaborate with peers to discuss observed timber characteristics.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum (Senior Secondary Technology Education)
State Unified Scheme of Work for Machine Wood Work SSS 1
Woodwork for Senior Secondary Schools by A.B. Olaitan and L.A. Adebayo
https://www.wood-database.com/softwoods-vs-hardwoods/
https://www.researchgate.net/publication/327702958_Common_West_African_Timber_Species

Instructional Materials

The teacher will teach this lesson with the aid of:

Timber comparison chart
Samples of softwood (e.g., Pine, Cedar) and hardwood (e.g., Iroko, Mahogany)
Whiteboard/Chalkboard and markers/chalk

Rationale for the Lesson

Understanding timber properties helps pupils choose the right wood for different projects, ensuring durability and suitability. It also enables them to identify various types of wood commonly found in their environment and the market, which is important for practical applications in woodworking.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of wood as a raw material and have seen various wooden objects.

Lesson Content/Board Summary

Properties of Timber

Difference Between Softwood and Hardwood

Timber is broadly classified into softwood and hardwood based on its botanical origin, not necessarily its actual hardness.

The following are differences between softwood and hardwood:

Botanical Origin: Softwoods come from coniferous trees (cone-bearing, needle-leafed trees that usually keep their leaves year-round), while hardwoods come from deciduous trees (broad-leafed trees that typically shed their leaves in autumn).
Growth Rate: Softwoods generally grow faster than hardwoods.
Density: Hardwoods are generally denser and harder than softwoods, though there are exceptions (e.g., Balsa is a hardwood but very soft).
Cell Structure: Hardwoods have complex pore structures (vessels) for water transport, visible as pores, while softwoods have simpler cell structures (tracheids).
Cost: Softwoods are generally less expensive due to faster growth and easier processing.
Applications: Softwoods are often used for construction, paper production, and general carpentry. Hardwoods are preferred for furniture, flooring, and fine woodworking due to their durability and aesthetics.

Physical Properties of Timber

The physical properties of timber describe its observable characteristics and behavior without changing its chemical composition.

The following are physical properties of timber:

Colour: The natural shade of the wood, which varies widely among species.
Lustre: The natural sheen or glossiness of the wood surface.
Grain: The pattern formed by the arrangement of wood fibers, which can be straight, interlocked, wavy, or spiral.
Texture: Refers to the relative size and uniformity of the wood cells, described as fine, medium, or coarse.
Odour: The distinctive smell of certain timbers, especially when freshly cut.
Density (Weight): The mass per unit volume of the wood, indicating its heaviness and often its strength.
Moisture Content: The amount of water present in the wood, affecting its stability and workability.
Shrinkage and Swelling: The tendency of wood to change dimension (shrink when drying, swell when absorbing moisture).
Hardness: The resistance of the wood to indentation or scratching.

Common West African Timbers

West Africa is home to a variety of valuable timber species.

The following are common West African timbers:

Iroko (Milicia excelsa): A durable hardwood, often used as a substitute for Teak, known for its resistance to rot and insects.
Mahogany (Khaya ivorensis, Khaya senegalensis): A reddish-brown hardwood, valued for furniture, boat building, and decorative work due to its attractive grain.
Obeche (Triplochiton scleroxylon): A very light-coloured, soft hardwood, easy to work, used for light furniture, interior joinery, and as a core veneer.
Sapele (Entandrophragma cylindricum): A reddish-brown hardwood with an interlocked grain, used for furniture, cabinetry, and decorative veneers.
Utile (Entandrophragma utile): Similar to Sapele but typically coarser, used for similar applications.

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, reviews the previous lesson, and introduces the new topic, “Properties of Timber,” by asking pupils to name some wooden items they see daily.
Pupils’ Activity: Pupils respond to the teacher’s questions and listen attentively.
Learning Point: Pupils are prepared for the new lesson.

Step 2: Explanation of Softwood and Hardwood

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains the botanical differences between softwood and hardwood, using the timber comparison chart and pointing out examples from the wood samples. The teacher highlights key differences like growth rate, density, and cell structure.
Pupils’ Activity: Pupils observe the chart and wood samples, ask questions, and take notes.
Learning Point: Pupils understand the fundamental classification of timber.

Step 3: Discussion of Physical Properties

Time: 10 minutes
Teaching Skill: Explanation/Observation
Teacher’s Activity: The teacher describes various physical properties of timber such as colour, grain, texture, density, and odour. For each property, the teacher uses the wood samples to demonstrate and allow pupils to observe these characteristics directly.
Pupils’ Activity: Pupils observe the wood samples, identify the described properties, and ask clarifying questions.
Learning Point: Pupils can identify and describe various physical properties of timber.

Step 4: Identification of West African Timbers

Time: 7 minutes
Teaching Skill: Identification/Lecture
Teacher’s Activity: The teacher names and briefly describes common West African timbers (e.g., Iroko, Mahogany, Obeche, Sapele), showing samples where available and explaining their typical uses.
Pupils’ Activity: Pupils listen, observe the samples, and note down the names and characteristics of the timbers.
Learning Point: Pupils can identify common West African timber species.

Step 5: Practical Identification

Time: 5 minutes
Teaching Skill: Practical Application
Teacher’s Activity: The teacher distributes various unmarked wood samples to groups of pupils and asks them to identify whether each is a softwood or hardwood and to describe some of its physical properties.
Pupils’ Activity: Pupils handle the samples, discuss their observations in groups, and attempt to identify the timber types and properties.
Learning Point: Pupils gain hands-on experience in distinguishing timber types and properties.

Step 6: Class Activity/Recap

Time: 3 minutes
Teaching Skill: Question and Answer
Teacher’s Activity: The teacher facilitates a quick question-and-answer session to reinforce the main points of the lesson, asking pupils to share their observations from the practical session.
Pupils’ Activity: Pupils answer questions and contribute to the discussion.
Learning Point: Pupils consolidate their understanding.

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 softwood and hardwood.
State three differences between softwood and hardwood.
List five physical properties of timber.
Mention two common West African timbers.

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 and gives pupils homework: “Research other common timbers found in Nigeria and list their properties.”
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: Pupils review the lesson’s main points and receive follow-up tasks.

Lesson Keywords

Softwood – Timber from coniferous trees, generally lighter and faster growing.
Hardwood – Timber from deciduous trees, generally denser and slower growing.
Grain – The pattern formed by the arrangement of wood fibers.
Texture – The relative size and uniformity of wood cells (fine, medium, coarse).
Density – The mass per unit volume of wood, indicating its heaviness.
Iroko – A durable West African hardwood, often used for furniture and outdoor applications.
Mahogany – A reddish-brown West African hardwood valued for fine furniture.

Differentiation

For visual learners, the timber comparison chart and actual wood samples will be emphasized. Kinesthetic learners will benefit from handling and examining the wood samples during the practical identification step. Auditory learners will benefit from the teacher’s explanations and class discussions. Pupils who grasp concepts quickly can be asked to identify more specific characteristics or research additional timber types, while those needing more support will receive focused guidance during group activities.

Note for teachers using this lesson plan

Ensure a variety of wood samples are available, including both softwood and hardwood, and ideally some common West African timbers. Encourage pupils to touch, smell, and closely observe the samples to appreciate the different physical properties. Safety precautions should be observed when handling wood samples, especially if they have rough edges.