🧪 The Wonderful World of Science
Class 10 – Chapter 1: Chemical Reactions and Equations
Learn how substances change in identity and properties, how to write balanced chemical equations, and explore the various types of chemical reactions.
🔄 What is a Chemical Reaction?
Everyday changes — milk turning sour, iron rusting, food getting digested — are examples of chemical reactions. A chemical reaction changes one or more substances into new ones with different properties.
📌 How Do You Know a Chemical Reaction Happened?
- ✅ Change in state
- ✅ Change in color
- ✅ Evolution of a gas
- ✅ Change in temperature
⚗️ Types of Chemical Reactions
- 🧩 Combination Reaction: Two or more reactants → one product
- 🔍 Decomposition Reaction: One substance breaks into two or more products
- 🔄 Displacement Reaction: A more reactive element replaces a less reactive one
- 🔁 Double Displacement Reaction: Exchange of ions, often forming a precipitate
- 🔥 Redox Reaction: Oxidation and reduction happen simultaneously
⚖️ Writing Balanced Chemical Equations
A chemical equation must follow the Law of Conservation of Mass — the number of atoms of each element must be equal on both sides.
Example:
Zn + H₂SO₄ → ZnSO₄ + H₂
💡 Real-Life Reactions
- 🧪 Respiration: Glucose + O₂ → CO₂ + H₂O + Energy (Exothermic reaction)
- 🌿 Photosynthesis: CO₂ + H₂O → Glucose + O₂ (Endothermic reaction)
- ⚙️ Rusting: Iron + Oxygen + Water → Rust (Corrosion)
- 🥫 Rancidity: Fats get oxidized, changing smell/taste
📘 Download Chapter
📊 Quick Quiz
- 1. Which of the following is not a sign of chemical reaction?
🔘 a) Change in color 🔘 b) Heat release 🔘 c) Breaking of glass 🔘 d) Formation of gas - 2. What type of reaction is: 2H₂ + O₂ → 2H₂O
🔘 a) Displacement 🔘 b) Combination 🔘 c) Decomposition 🔘 d) Double Displacement - 3. What is the process of rusting an example of?
🔘 a) Combustion 🔘 b) Displacement 🔘 c) Oxidation 🔘 d) Decomposition
🔬 Activities You Can Try
- 🧪 Heat ferrous sulphate and observe changes
- 💡 Perform electrolysis of water with a battery
- 🔄 Mix barium chloride with sodium sulphate and watch for precipitate
- 🔥 Observe copper turn black when heated (Cu → CuO)
📚 Summary
- ✅ Chemical reactions form new substances with different properties
- ✅ They must be written as balanced equations
- ✅ There are different types: combination, decomposition, displacement, etc.
- ✅ Redox reactions involve gain/loss of oxygen or hydrogen
🎉 Chemistry in Action!
From firecrackers to baking, chemistry is everywhere. Understand reactions, balance them, and experiment safely!