combination 1

 Absolutely, Mayank! Here is a student-friendly explanation of Section 1.2.1: Combination Reaction from Class 10 Science, Chapter 1 (Chemical Reactions and Equations), written in a format ideal for teaching, notes, or classroom revision.

🔗 1.2.1 Combination Reaction

(From NCERT Class 10 Science – Chapter 1)

🎯 What is a Combination Reaction?

A combination reaction is a reaction in which two or more substances combine to form a single new product.

📘 General Formula:

A+B→ABA + B \rightarrow AB

✅ Key Feature: Only one product is formed.

🧪 Example 1: Calcium oxide reacts with water

CaO(s)+H2O(l)→Ca(OH)2(aq)+Heat\text{CaO} (s) + \text{H}_2\text{O} (l) \rightarrow \text{Ca(OH)}_2 (aq) + \text{Heat}

  • Calcium oxide (quick lime) combines with water to form calcium hydroxide (slaked lime).

  • This reaction is exothermic — it releases heat.

  • Used in whitewashing walls.

📝 Observation: The container becomes hot due to heat released.

🧪 Example 2: Burning of coal

C(s)+O2(g)→CO2(g)\text{C} (s) + \text{O}_2 (g) \rightarrow \text{CO}_2 (g)

  • Carbon reacts with oxygen to form carbon dioxide.

  • Energy is released → it's an exothermic combination reaction.

🧪 Example 3: Hydrogen + Oxygen → Water

2H2(g)+O2(g)→2H2O(l)2\text{H}_2 (g) + \text{O}_2 (g) \rightarrow 2\text{H}_2\text{O} (l)

  • Hydrogen and oxygen gases combine to form liquid water.

  • A clean example of a combination reaction with energy release.

💡 Characteristics of Combination Reactions:

  • Only one product is formed.

  • Often exothermic (releases heat).

  • Can involve elements or compounds as reactants.

📘 CBSE Exam Tip:

You may be asked to:

  • Define combination reaction

  • Write an example

  • Mention its nature (exothermic or not)

  • Give daily-life uses (like whitewashing)

📖 Real-Life Connection:

✅ Whitewashing of walls:
CaO + H₂O → Ca(OH)₂
Slaked lime reacts with CO₂ in air to form CaCO₃, which gives a shiny finish to walls.

✅ Combustion of fuels
Like C + O₂ → CO₂, which powers engines and home stoves.

🎤 Closing Thought:

“Combination reactions are nature’s way of building things — combining two parts to create something new, often with a burst of energy!”

Would you like a quick worksheet, labelled diagram, or animated demo link for combination reactions?

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