CBSE Class 10 Science Chapter 1 Chemical Reactions and Equations

Chemical Reactions and Equations is a chapter in your science subject. Radhe Radhe to all my dear children! You all will have to work very hard for your board exams to get good marks. In this post, I will try to cover all the important topics of your 10th-grade science syllabus so that you can understand and remember them.

Chemical Reactions and Equations, which is your first chapter, falls under the chemistry section of science. All the information you need to study in this chapter will be found in this post.

Key Content of Chapter 1 Chemical Reactions and Equations

1️⃣ Chemical Reaction – Basic Idea

• Jab ek ya zyada substances chemical change se naye substances banate hain
• Daily life examples:
  • Milk → curd
  • Iron rusting
  • Grapes fermentation
  • Cooking & digestion of food
  • Respiration

➡️ In sab me new substance banta hai → chemical reaction

2️⃣ How to Identify a Chemical Reaction

Chemical reaction ke signs:

• Change in colour
• Change in state
• Evolution of gas
• Change in temperature
• Formation of precipitate

3️⃣ Chemical Equation

• Reaction ko words ya symbols me likhna
• Reactants → Products
• LHS = reactants
• RHS = products

Example (word):
Magnesium + Oxygen → Magnesium oxide

Example (symbol):
Mg + O₂ → MgO

4️⃣ Skeletal & Balanced Chemical Equation ⭐⭐⭐

• Skeletal equation: atoms equal nahi
• Balanced equation: har element ke atoms LHS = RHS

➡️ Law of Conservation of Mass

• Mass create ya destroy nahi hota

5️⃣ Steps to Balance Chemical Equations ⭐⭐⭐

• Atoms count karo
• Coefficients change karo (formula nahi)
• Hit-and-trial method
• Smallest whole number use karo

6️⃣ Physical State Symbols

• (s) → solid
• (l) → liquid
• (g) → gas
• (aq) → aqueous

➡️ Kabhi-kabhi reaction conditions bhi likhte hain (heat, light, catalyst)

7️⃣ Types of Chemical Reactions ⭐⭐⭐

(a) Combination Reaction

• 2 ya zyada reactants → 1 product
• Example:
  CaO + H₂O → Ca(OH)₂
• Mostly exothermic

(b) Decomposition Reaction

• 1 compound → 2 ya zyada products
• Energy required (heat / light / electricity)

Types:

• Thermal decomposition
• Photochemical decomposition
• Electrolytic decomposition

(c) Displacement Reaction

• Zyada reactive element, kam reactive ko replace karta hai
• Example:
  Fe + CuSO₄ → FeSO₄ + Cu

(d) Double Displacement Reaction

• Ions exchange hote hain
• Example:
  Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl

➡️ Agar insoluble solid bane → Precipitation reaction

8️⃣ Exothermic & Endothermic Reactions

• Exothermic → heat release
  • Burning
  • Respiration
• Endothermic → heat absorb
  • Decomposition reactions

9️⃣ Oxidation & Reduction ⭐⭐⭐

• Oxidation:
  • Gain of oxygen
  • Loss of hydrogen
• Reduction:
  • Loss of oxygen
  • Gain of hydrogen

➡️ Dono saath hote hain → Redox reaction

🔟 Corrosion

• Metals ka slow damage due to air & moisture
• Example:
  • Rusting of iron
  • Green layer on copper
  • Black coating on silver

➡️ Heavy economic loss

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