Science Class 10 (HSLC 2025–26), Chapter 1, CHEMICAL REACTION AND EQUATION.

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Very Short Answer (1 Mark)

1. What is a chemical equation?
2. What do you mean by a balanced chemical equation?
3. Write the balanced chemical equation for the reaction of quicklime with water.
4. What is the chemical formula of quicklime, slaked lime, and bleaching powder?
5. Define oxidation and reduction with examples.
6. What is a displacement reaction? Give one example.
7. Name the gas evolved when zinc reacts with dilute HCl.
8. Write the balanced chemical equation for the decomposition of ferrous sulphate crystals on heating.
9. Define a photochemical reaction with one example.
10. What is the difference between exothermic and endothermic reactions?

Short Answer (2–3 Marks)

1. Write the balanced chemical equation for the reaction between hydrogen and chlorine to form hydrogen chloride.
2. Balance the following equation:
   • Al + O₂ → Al₂O₃
   • Fe + H₂O → Fe₃O₄ + H₂
3. What happens when zinc granules react with dilute sulphuric acid? Write the balanced chemical equation.
4. State the characteristics of a chemical reaction.
5. Differentiate between combination reaction and decomposition reaction with one example each.
6. Give one example each of:
   • Combination reaction
   • Double displacement reaction
   • Decomposition reaction
   • Displacement reaction
7. Explain the corrosion of iron with a chemical reaction.
8. Why is photosynthesis considered an endothermic reaction? Write its balanced chemical equation.
9. What is rancidity? How can it be prevented?
10. Write the balanced chemical equation for the reaction of sodium carbonate with dilute HCl.

Long Answer (4–5 Marks)

1. What is a chemical reaction? Write four important types of chemical reactions with suitable examples.
2. What is oxidation and reduction? Explain with two examples each.
3. Explain the following with chemical equations:
   • Rusting of iron
   • Action of heat on ferrous sulphate crystals
   • Action of light on silver chloride
4. Balance the following equations and identify the type of reaction:
   • CaO + H₂O → Ca(OH)₂
   • 2KClO₃ → 2KCl + 3O₂
   • Zn + CuSO₄ → ZnSO₄ + Cu
   • Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
5. Write any four differences between physical and chemical changes with examples.

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