Welcome to GattPrep!
Hello scientist! 👋🏽
Have you ever seen brown, flaky stuff on a gate, car, or bicycle? That’s rust. It eats away at iron and steel, weakening buildings, tools, and vehicles. Rusting is a chemical reaction—and if we don’t control it, it can cause big damage.
In this lesson, you’ll learn how rust forms, why it happens, and how we can stop it using simple and scientific methods. Let’s dive into the chemistry behind the rust you see around you every day!
📘 Core Concepts
✅ Two key things are always needed:
Oxygen (from air)
Water (moisture or humidity)
🧪 Experiments show:
Iron in dry air = No rust
Iron in dry water = No rust
Iron in moist air = Rust forms
| Factor | How It Affects Rusting |
|---|---|
| Salt (e.g. seawater) | Increases conductivity – speeds rusting |
| Acids or bases | React faster with iron, speeding rust |
| Heat | Higher temperatures accelerate chemical reactions |
| Pollution | Acidic gases like SO₂ make air more reactive |
Weakens metal structures
Makes tools and machinery unusable
Costs money to repair or replace
Can cause accidents (e.g. bridge collapse, pipe bursts)
🛡️ Common Methods to Prevent Rusting
| Method | Description |
|---|---|
| Painting | Coats the iron to block air and moisture |
| Greasing/Oiling | Prevents water from contacting the surface |
| Galvanizing | Coating with zinc (zinc rusts first, protecting iron) |
| Electroplating | Using electricity to coat iron with metals like chrome |
| Alloying | Mixing with rust-resistant metals (e.g. stainless steel) |
| Cathodic Protection | Attaching a more reactive metal (like zinc) nearby to corrode first |
👨🏽🔬 Examples in Everyday Life
Bicycle chains: Oiled to prevent rust
Roofing sheets: Galvanized (zinc-coated) iron
Car bodies: Painted or made of stainless steel
Underground pipes: Use cathodic protection
📐 Sample Problem Walkthrough
🧠 Problem: A farmer notices rust on his farm tools after the rainy season. Suggest THREE ways he could prevent this from happening again.
✅ Step-by-Step Solution:
Grease or oil the tools after use.
Store them in a dry place to reduce moisture exposure.
Paint or coat the metal parts to seal out air and water.
✔️ Answer: The farmer should apply oil, keep tools dry, and coat them with paint to prevent rusting.
✍🏽 Practice Exercises
1. Fill in the blanks
(a) Rusting requires both ______ and ______.
(b) A method that involves coating iron with zinc is called ______.
✅ Answers:
(a) oxygen, water
(b) galvanizing
2. Match the Method to Its Action
| Prevention Method | Action Taken |
|---|---|
| (i) Electroplating | A. Coats iron with zinc |
| (ii) Galvanizing | B. Covers surface with oil |
| (iii) Greasing | C. Uses electricity to coat with another metal |
✅ Answers:
(i) → C
(ii) → A
(iii) → B
3. Short Answer
Why does iron rust faster in coastal areas?
✅ Sample Answer:
Coastal areas have salty air and high humidity, which increase the presence of moisture and electrolytes, speeding up the rusting process.
🌀 Recap
Today you learned that:
Rusting is a chemical reaction involving iron, water, and oxygen.
Rust weakens metals and causes economic and safety problems.
Rusting is faster in salty, acidic, or moist environments.
Prevention methods include painting, greasing, galvanizing, alloying, and more.
💭 Reflection Prompt
Think of something metallic around your home or school. Has it started rusting? How could you protect it? Write your answer and suggest the most practical prevention method.
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