Corrosion and Rancidity

 Certainly, Mayank. Here's a well-organized and CBSE Class 10–level explanation of Sections 1.3.1 (Corrosion) and 1.3.2 (Rancidity), written to be exam-ready, easily teachable, and suitable for digital or classroom use.

📘 1.3.1 Corrosion

(Class 10 Science – Chapter: Chemical Reactions and Equations)

✅ What is Corrosion?

Corrosion is the slow wearing away of a metal due to the action of moisture, air, acids, and other environmental substances on its surface.

🔍 Examples of Corrosion:

Metal Observation
Iron Forms a reddish-brown flaky coating (rust)
Copper Forms a green coating of copper carbonate
Silver Develops a black coating of silver sulphide

🧪 Chemical Reaction of Rusting:

4Fe+3O2+xH2O→2Fe2O3⋅xH2O4\text{Fe} + 3\text{O}_2 + x\text{H}_2\text{O} \rightarrow 2\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}

(Rust: Hydrated iron(III) oxide)

⚠️ Why is Corrosion Harmful?

  • Weakens metal structures like bridges, buildings, and vehicles

  • Damages iron objects such as railings, pipelines, and ships

  • Leads to huge financial losses every year

🛡️ Prevention of Corrosion:

  • Painting

  • Oiling and greasing

  • Galvanisation (coating iron with zinc)

  • Electroplating

  • Alloying (e.g., stainless steel)

📘 1.3.2 Rancidity

✅ What is Rancidity?

Rancidity is the condition when fats and oils get oxidised, resulting in bad smell and taste in food items.

🧠 Why does it happen?

  • Due to oxidation of unsaturated fatty acids present in food

  • More common in food stored for long periods or exposed to air

🧪 Examples of Rancid Foods:

  • Old cooking oil

  • Spoiled ghee or butter

  • Stale snacks (like chips)

🛡️ Prevention of Rancidity:

Method Explanation
Adding antioxidants Chemicals like BHA, BHT delay oxidation
Airtight packaging Reduces contact with air and moisture
Refrigeration Slows down oxidation by lowering temperature
Nitrogen flushing Chips packets are filled with nitrogen gas to remove oxygen

🧠 CBSE Exam Tip:

Q: What is corrosion? Give one method to prevent it.
✅ Answer:
Corrosion is the gradual destruction of metals due to environmental effects like moisture and air.
Example: Rusting of iron.
Prevention: Galvanisation

Q: What is rancidity? How can it be prevented?
✅ Answer:
Rancidity is the oxidation of fats and oils in food, leading to bad taste and smell.
Prevention: Use of antioxidants, airtight containers, or flushing with nitrogen gas

Let me know if you’d like a visual diagram, summary table worksheet, or animated video script to teach this effectively on www.dasklibro.com.

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