Lesson Notes By Weeks and Term v4 - SHS 3
INTRODUCTION TO VEHICLE TECHNOLOGY
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
INTRODUCTION TO VEHICLE TECHNOLOGY
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Applied Technology
Class: SHS 3
Term: 1st Term
Week: 4
Grade code: 3.1.1.LI.6
Strand code: 1
Sub-strand code: 2
Content standard code: 3.1.1.CS.1
Indicator code: 3.1.1.LI.6
Theme: AUTOMOTIVE TECHNOLOGY
Subtheme: INTRODUCTION TO VEHICLE TECHNOLOGY
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Start the lesson by asking students about the smoke they see coming from vehicles. "Why do some vehicles, especially older trotros or trucks, release thick, dark, and smelly smoke, while many newer private cars release exhaust that is almost invisible and odourless?" This difference is largely due to the vehicle's exhaust system, and a very important component inside it called the catalytic converter. This "magic box" is a crucial part of modern vehicles. It acts like a chemical filter, cleaning the harmful gases produced by the engine before they enter our environment.
(35 minutes)
This section is the core of the lesson. The teacher will use a mix of lecturing, diagrams, and asking questions to engage the students. Part 1: What is a Catalytic Converter and Where is it Found? Definition: A catalytic converter is an exhaust emission control device that converts toxic (poisonous) gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants. Location: It is located in the exhaust system, usually between the exhaust manifold (where hot gases leave the engine) and the muffler (the box at the back that reduces noise). (Use a diagram or go outside to a real vehicle if possible). Let’s trace the path of the exhaust gas: Engine Cylinders: Fuel and air burn. Exhaust Manifold: Collects the hot, dirty gases from the cylinders. Catalytic Converter: The gases pass through here and are chemically changed (cleaned). Muffler/Silencer: Reduces the noise of the exhaust. Tailpipe: The cleaned, quieter gases exit the vehicle.
*(Teacher sketches a simple diagram on the board showing: Engine -> Manifold -> Catalytic Converter -> Muffler -> Tailpipe)* Part 2: The Function - How Does It "Clean" the Exhaust?
The catalytic converter doesn't work like a physical filter (like a water filter trapping dirt). Instead, it causes chemical reactions. The Problem: The engine's combustion process is not perfect. It produces harmful gases: Carbon Monoxide (CO): A poisonous gas that is colourless and odourless. It's dangerous because it reduces the oxygen-carrying capacity of our blood. Hydrocarbons (HC): Unburnt fuel vapours. They contribute to smog, which can cause breathing problems. You can often smell this from poorly maintained vehicles. Nitrogen Oxides (NOx): A group of gases (like NO and NO₂) formed when nitrogen in the air reacts under high heat and pressure inside the engine. They contribute to smog and acid rain. The Solution (The "Catalyst"): Inside the converter is a ceramic honeycomb structure coated with very thin layers of precious metals. These metals are catalysts. A catalyst is a substance that speeds up a chemical reaction without being used up in the process. The main catalysts used are: Platinum (Pt) and Palladium (Pd): These are *oxidation* catalysts. Rhodium (Rh): This is a *reduction* catalyst. The Chemical Reactions (Simplified): The hot exhaust gases (which need to be very hot, around 400°C, for the converter to work) flow through the honeycomb. As the gases touch the catalyst-coated surfaces, two main types of reactions happen: Oxidation (Adding Oxygen): The Platinum and Palladium help the harmful Carbon Monoxide (CO) and Hydrocarbons (HC) react with oxygen (O₂) to become harmless substances. `2CO + O₂ → 2CO₂` (Carbon Monoxide becomes Carbon Dioxide) `HC + O₂ → H₂O + CO₂` (Hydrocarbons become Water and Carbon Dioxide) Reduction (Removing Oxygen): The Rhodium strips oxygen atoms from the toxic Nitrogen Oxides (NOx). `2NOx → N₂ + O₂` (Nitrogen Oxides become harmless Nitrogen gas and Oxygen) Analogy: Think of the catalytic converter as a busy marketplace. The catalysts (Platinum, Palladium, Rhodium) are the market women who quickly bring buyers and sellers (the molecules) together to make a trade (a chemical reaction) happen, turning bad products (pollutants) into good ones (harmless gases). Part 3: Types of Catalytic Converters