Class 7 Science Chapter 5 Changes Around Us Physical and Chemical Notes | Curiosity 2026-27 | Amresh Academy

 

🌟 Class 7 Science Curiosity – Chapter 5 Notes

🔄 Changes Around Us: Physical and Chemical | Amresh Academy

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📘 Introduction

In our daily life, we observe many changes around us 🔄

👉 These changes are mainly of two types:

• Physical Changes
• Chemical Changes

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⚙️ 1. Types of Changes

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🔹 Physical Changes

👉 Change in:

• Shape
• Size
• State

❌ No new substance is formed

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📌 Examples:

• ❄️ Melting ice
• 📄 Folding paper
• 💧 Boiling water
• 🎈 Inflating a balloon

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🔹 Chemical Changes

👉 New substance is formed through a chemical reaction 🧪

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📌 Examples:

• 🔥 Burning wood
• 🧱 Rusting iron
• 🧪 Vinegar + baking soda
• 🥛 Curdling milk

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🧠 2. Characteristics

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⚪ Physical Changes:

• No new substance
• Often reversible

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🔴 Chemical Changes:

• New substances formed
• Usually irreversible

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🧪 3. Key Examples

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🔹 Physical Changes:

• ❄️ Melting ice cubes
• 🥕 Cutting vegetables
• 👕 Drying clothes

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🔹 Chemical Changes:

🧱 Rusting:

👉 Iron + Oxygen → Iron oxide

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🔥 Combustion:

👉 Burning magnesium →

Magnesium oxide + Heat + Light

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🧪 Lime Water Test:

👉 CO₂ + Lime water → Calcium carbonate (milky)

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🔥 4. Combustion

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👉 A chemical reaction with oxygen

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⚡ Requirements:

• 🔥 Fuel
• 🌬️ Oxygen
• 🌡️ Ignition temperature

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🕯️ Example:

👉 Burning candle:

• Wax melting → Physical change
• Wax burning → Chemical change

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🔁 5. Reversible vs Irreversible Changes

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✔️ Reversible Changes:

👉 Can be reversed

• Ice ↔ Water
• Water ↔ Steam

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❌ Irreversible Changes:

👉 Cannot be reversed

• Burning wood
• Making popcorn

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🎯 6. Desirable vs Undesirable Changes

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✔️ Desirable Changes:

👉 Useful changes

• Cooking food 🍲
• Ripening fruits 🍎

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❌ Undesirable Changes:

👉 Harmful changes

• Rusting 🧱
• Food spoilage 🍞

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⚠️ Note:

👉 Some changes depend on situation

(e.g., decomposition can be useful or harmful)

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🌍 7. Natural Changes

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🪨 Weathering:

👉 Formation of soil

• Physical → Breaking rocks
• Chemical → Rusting in rocks

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🌊 Erosion:

👉 Movement of soil

• Caused by wind 🌬️
• Or water 💧

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📌 Final Summary

👉 Changes around us are of two main types:

• Physical → No new substance
• Chemical → New substance formed

👉 Understanding changes helps us in:

• Daily life
• Industry
• Environment 🌍

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✨ Perfect for revision + exams + quick understanding 🚀

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