Lesson Notes By Weeks and Term v4 - JHS 1

Lesson Video

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Performance objectives

• Explain the law of conservation of energy.
• Identify different forms of energy.
• Illustrate energy transformation using diagrams.
• Discuss real-life examples of energy conservation in Ghana.

Lesson summary

Energy makes things happen—lighting our homes, charging phones, cooking food, moving vehicles, and running machines in farms and small businesses. In Ghana, learners see energy changes daily: a dry cell powers a torch, LPG burns to cook, and electricity runs fans and TVs. The key idea in this lesson is conservation of energy: energy is not created or destroyed; it only changes form. Understanding this helps learners explain why devices get hot, why batteries run down, and why we must use energy wisely.

Lesson notes

A. What is Energy? Energy is the ability to do work or cause change. Examples of changes caused by energy: Moving an object (motion) Heating water Producing light Making sound B. Forms of Energy (JHS level) Common forms you will meet: Chemical energy: stored in food, fuel (petrol, charcoal, LPG), and batteries (dry cells). Electrical energy: energy carried by electric current (mains electricity, power banks). Light energy: from the sun, bulbs, torchlight. Heat (thermal) energy: hot objects, cooking, friction. Sound energy: from speakers, drums, horns. Kinetic energy: energy of moving objects (a moving bicycle). Potential energy: stored due to position (water behind a dam, a raised stone). C. Energy Conversion (Transformation) Energy conversion means changing energy from one form to another.

Examples in Ghanaian context Torchlight (dry cell + bulb) Chemical energy (battery) → Electrical energy → Light energy + Heat energy (The bulb becomes warm: that is heat energy.) Charcoal stove Chemical energy (charcoal) → Heat energy + Light energy (glow) Some energy also becomes heat that spreads into the air (not all heats the pot). Mobile phone Chemical energy (battery) → Electrical energy → Light (screen) + Sound (speaker) + Heat (phone warms) D. The Law of Conservation of Energy (Indicator Focus) Law/Principle: > Energy cannot be created or destroyed; it can only be converted from one form to another. > In a closed system, the total amount of energy remains the same. What is a “Closed System” (Simple meaning for JHS)? A closed system is one where we consider all energy changes inside it, and no energy is added from outside and none is removed without being counted.

Example: If we consider *battery + bulb + wires + surrounding air inside a box* as our system, then heat and light are still within the system (they are not “missing”; they are part of the total energy). E. “Useful” vs “Wasted” Energy (Important clarification) Useful energy: the form of energy we want from a device. Wasted energy: energy converted into forms we do not want (often heat and sound).

Key point: Wasted energy is not destroyed. It is still energy—just not helpful for the intended task.

Evaluation guide

• Explain the law of conservation of energy by using diagram to show
• that in a closed system the value of chemical energy, for example
• in dry cell which changes into electrical, heat and light energy will
• remain the same. Digital Literacy (DL), Creativity and Innovation