Lesson Notes By Weeks and Term v4 - JHS 3
CONVERSION AND CONSERVATION OF ENERGY
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CONVERSION AND CONSERVATION OF ENERGY
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Science
Class: JHS 3
Term: 2nd Term
Week: 12
Grade code: B9.4.3.1.2
Strand code: 4
Sub-strand code: 3
Content standard code: B9.4.3.1
Indicator code: B9.4.3.1.2
Theme: FORCES AND ENERGY
Subtheme: CONVERSION AND CONSERVATION OF ENERGY
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Energy makes things happen: lighting our homes, cooking food, charging phones, moving vehicles, pumping water, and running machines in small businesses. In Ghana, where electricity bills, fuel costs, and “dumsor” experiences affect daily life, understanding energy conversion (how energy changes form) and energy conservation (how energy is saved and used wisely) helps learners make smart choices at home, in school, and in the community.
A. What is Energy? Energy is the ability to do work or cause change. Common forms of energy learners meet daily: Chemical energy: stored in food, batteries, petrol, LPG, charcoal. Electrical energy: from ECG supply, solar panels, generators. Light (radiant) energy: sunlight, bulbs, TV screens. Heat (thermal) energy: hot water, iron, charcoal stove. Sound energy: speakers, drums, horns. Kinetic energy: moving objects (running, moving car, spinning fan). Potential energy: stored due to position (water in a tank, object on a shelf).
B. Energy Conversion (Energy Transformation) Energy conversion is the process where energy changes from one form to another. Everyday examples (Ghanaian context) Torchlight (battery torch) Chemical energy (battery) → Electrical energy → Light energy + Heat energy *Note:* Some energy becomes heat; not all becomes light. Electric fan Electrical energy → Kinetic energy (spinning blades) + Sound energy + Heat energy (motor warms) Charcoal stove Chemical energy (charcoal) → Heat energy + Light energy (glow) Heat energy → cooks food (increases internal energy of food/water) Car/Okada Chemical energy (petrol) → Heat energy (engine combustion) → Kinetic energy (movement) + Sound + Heat (wasted) Solar lamp Light energy (sun) → Electrical energy (solar panel) → Chemical energy (battery storage) → Light energy (lamp at night)
Key idea: In real devices, energy conversions are not 100% efficient. Some energy becomes less useful forms (often heat and sound).
C. Energy Conservation (Two Meanings—Teach Both Clearly) 1) Conservation of Energy (Scientific Law) Law of Conservation of Energy: Energy cannot be created or destroyed; it can only be converted from one form to another. So, the total energy in a closed system remains constant.