Class 10 chemistry chapter 1

Class 10 Chemistry Chapter 1 – Chemical Reactions and Equations

📘 Class 10 Chemistry – Chapter 1

Chemical Reactions and Equations

1. What is Chemistry?

Chemistry is the branch of science that deals with the composition, structure, properties and changes of matter.

2. Chemical Reaction

A chemical reaction is a process in which one or more substances (reactants) are converted into new substances (products) with different properties.
Example:
Magnesium + Oxygen → Magnesium Oxide

Observations during Chemical Reaction

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

3. Chemical Equation

A chemical equation is the symbolic representation of a chemical reaction using symbols and formulas.
Word Equation:
Calcium Carbonate → Calcium Oxide + Carbon Dioxide
Chemical Equation:
CaCO₃ → CaO + CO₂

4. Balanced Chemical Equation

Unbalanced:
H₂ + O₂ → H₂O
Balanced:
2H₂ + O₂ → 2H₂O
Law of Conservation of Mass:
Mass can neither be created nor destroyed in a chemical reaction.

5. Steps to Balance a Chemical Equation

Fe + H₂O → Fe₃O₄ + H₂
  • Balance metal atoms first
  • Then non-metals
  • Hydrogen and oxygen at last
Balanced Equation:
3Fe + 4H₂O → Fe₃O₄ + 4H₂

6. Types of Chemical Reactions

1. Combination Reaction

CaO + H₂O → Ca(OH)₂
A + B → AB

2. Decomposition Reaction

CaCO₃ → CaO + CO₂
AB → A + B

3. Displacement Reaction

Zn + CuSO₄ → ZnSO₄ + Cu
A + BC → AC + B

4. Double Displacement Reaction

Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl

5. Redox Reaction

Oxidation = Loss of electrons / Gain of oxygen
Reduction = Gain of electrons / Loss of oxygen
CuO + H₂ → Cu + H₂O

7. Corrosion

Corrosion is the slow destruction of metals by air, moisture or chemicals.
Rusting of Iron:
4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O
Iron + Air + Water → Rust

Prevention of Rusting

  • Painting
  • Oiling and greasing
  • Galvanisation
  • Alloying

8. Rancidity

Rancidity is the oxidation of fats and oils in food causing bad smell and taste.

Prevention

  • Airtight containers
  • Refrigeration
  • Adding antioxidants
  • Nitrogen flushing

9. Important Exam Points ⭐

  • Always balance equations
  • Use state symbols (s), (l), (g), (aq)
Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

10. One Line Revision

  • Chemical reaction → New substance formation
  • Oxidation → Loss of electrons
  • Reduction → Gain of electrons
  • Rust → Hydrated iron oxide

✅ Chapter 1 Complete

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