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Subject: General Science
Semester: 1
Period: 1
Week: 5
School Name:
Teacher’s Name:
Subject: General Science
Grade Level: Grade 7
Date:
Week 5 Lesson Duration: 45 minutes
Week & Period: Week 5, Period 1
Topic: Changes in Matter & Fuels
Sub-topic: Physical and Chemical Changes, Types of Fuels
Learning Objectives
By the end of the lesson, students should be able to:
- Differentiate between physical and chemical changes in matter.
- Describe the properties and energy involvement in physical and chemical changes.
- Identify and classify fuels as solid, liquid, or gaseous, and explain their uses with examples relevant to Liberia.
Previous Knowledge
Students already know:
• Matter exists in three states: solid, liquid, gas.
• Matter can combine to form compounds and mixtures.
Instructional Materials
• Textbook: General science textbooks for Grade 7
• Teaching aids: Samples for experiments (ice, water, candle, paper, ethanol), charts of fuel types and uses
• Students' notebooks and writing materials
Lesson Development – ABC Model
A – Anticipation (Warm-up / Starter)
Time: 5–10 minutes
Activity: The teacher will ask the class:
• Can you give an example of something that changes shape or appearance without forming a new substance?
• Have you seen something burning or rusting? What do you think happens to the matter?
The teacher will record their responses on the board.
Teacher’s Role: Facilitate discussion and correct misconceptions.
Learner’s Role:
• Share observations from daily life about changes in matter.
• Participate actively in discussion.
B – Building Knowledge (Main Lesson Body)
Time: 25–30 minutes
Teacher’s Role
- Define Physical Change
- A physical change is a change in the form or appearance of matter, but no new substance is formed.
- Properties such as shape, size, state, or texture may change, but the composition remains the same.
- Energy involvement: Usually requires or absorbs heat, but only affects physical state, not chemical composition.
- Examples:
- Melting ice into water.
- Boiling water into steam.
- Dissolving sugar in tea.
- Cutting wood into smaller pieces.
- Liberian context examples:
- Melting shea butter under heat.
- Evaporation of puddles after rainfall.
- Crushing rocks into gravel for road construction.
- Define Chemical Change
- A chemical change is a change in matter that produces a new substance with new properties.
- Cannot easily be reversed.
- Energy involvement: Often involves release or absorption of energy (light, heat, sound).
- Examples:
- Burning paper → ash and smoke are new substances.
- Rusting iron in humid air.
- Cooking rice → raw rice turns into soft cooked rice.
- Liberian context examples:
- Burning charcoal in cook stoves.
- Rusting of zinc roofing sheets in coastal towns.
- Fermentation of palm wine.
- Compare Physical and Chemical Changes (Side-by-Side Table)
|
Feature |
Physical Change |
Chemical Change |
|
New substance formed? |
❌ No |
✅ Yes |
|
Reversibility |
Often reversible (ice ↔ water) |
Usually irreversible (burnt wood → ash) |
|
Energy involvement |
Usually requires small amount of heat |
Often releases or absorbs large amounts of energy |
|
Examples |
Boiling, melting, dissolving, cutting |
Burning, rusting, fermentation, cooking |
- Introduce Fuels
Explain that fuels are substances burned to produce energy (heat, light, or motion).
- Solid Fuels:
- Examples: firewood, charcoal, coal.
- Composition: mostly carbon-based.
- Uses: cooking, heating, iron smelting.
- Liberian examples: Charcoal stoves in Monrovia, firewood in rural households.
- Liquid Fuels:
- Examples: petrol (gasoline), kerosene, diesel.
- Properties: burn easily, transportable, higher energy output than solids.
- Uses: powering cars, lighting lanterns, generators.
- Liberian examples: Petrol for taxis and kekeh (tricycles); kerosene lamps in villages.
- Gaseous Fuels:
- Examples: Liquefied Petroleum Gas (LPG), natural gas, biogas.
- Properties: clean, efficient, high heat value, stored under pressure in cylinders.
- Uses: cooking, heating, some vehicles.
- Liberian examples: LPG cylinders used in urban homes for cooking; biogas projects in some agricultural communities.
- Highlight Local Relevance of Fuels in Liberia
- Over 80% of households rely on charcoal and firewood → contributes to deforestation.
- Liquid fuels (petrol, diesel) are vital for transportation and electricity generation.
- Gaseous fuels are cleaner but less common in rural Liberia due to cost and availability.
- Environmental impact: Using charcoal and firewood causes forest depletion and indoor air pollution.
- Demonstrations (Simple and Safe)
- Physical change demo: Show melting of ice cube or dissolving salt in water.
- Chemical change demo: Burn a small piece of paper to show ash, smoke, and energy release.
- Fuel demonstration (discussion-based, not actual burning in class): Show samples/pictures of charcoal, kerosene, and LPG cylinder; ask learners to identify their uses.
Learners’ Activities
- Observe teacher’s demonstrations and record key observations.
- Participate in guided discussion: distinguish between physical and chemical changes.
- Suggest local Liberian examples of physical and chemical changes.
- Classify fuels into solid, liquid, or gas and give one practical use of each.
- Group work: Match real-life activities (e.g., cooking with charcoal, rusting zinc sheets, melting butter) with physical or chemical change.
Assessment Checks
- Oral Questions:
- “Is melting ice a physical or chemical change? Why?”
- “When zinc sheets rust, is that a physical or chemical change?”
- Quick Written Check:
- Define physical change and give two examples.
- Define chemical change and give two examples.
- List one solid, one liquid, and one gaseous fuel, with a use of each.
- Practical: Teacher holds up an item (charcoal, water, balloon, iron nail) and students classify as physical change, chemical change, or fuel type.
Notes (Expanded & Detailed)
- Energy involvement:
- Physical change → usually small amount of heat needed (e.g., melting, evaporation).
- Chemical change → involves large energy exchange (heat, light, gas release).
- Environmental link:
- Over-reliance on solid fuels (charcoal, firewood) → deforestation + air pollution.
- Cleaner fuels (LPG, biogas) reduce health risks but are expensive.
- Practical importance:
- Understanding changes in matter helps in cooking, farming, mining, and industry.
- Knowledge of fuels helps in energy planning, environmental protection, and sustainable living in Liberia.
C – Consolidation (Conclusion & Assessment)
Time: 5–10 minutes
Summary:
• The teacher will ask students to recall:
- Definitions of physical and chemical changes
- Examples and energy involvement in each change
- Types of fuels and their uses
Evaluation Method (Expanded):
• Exit slip/quiz: Students will write short answers to:
- Give one example each of a physical and chemical change.
- Classify charcoal, petrol, and LPG as solid, liquid, or gaseous fuels.
- Explain one use of each type of fuel in Liberia.
Teacher will collect and quickly review for understanding.
• Provide oral feedback before class ends.
Assignment (Expanded): Follow-up Activity:
• Observe two changes at home or school: one physical and one chemical. Record the change, energy involved, and type of change.
• List five fuels used in Liberia and describe their form and use.
Differentiation / Inclusive Strategies
• Struggling Learners: Use clear demonstrations and simple examples for classification.
• Advanced Learners: Encourage research on renewable vs non-renewable fuels.
• Students with Disabilities: Provide hands-on participation in demonstrations and peer support.
Teacher’s Reflection (After Class)
• What worked well? ______________________________________________________
• What needs improvement? _________________________________________________
• Students’ engagement level: □ High □ Medium □ Low