Looking for accurate SEBA Class 10 Science Chapter 1 (Chemical Reactions and Equations) inside and in-text question solutions for the 2026–27 academic year? Access extra short questions, chemical equation balancing steps, and important internal notes designed to help you score 100% in your HSLC board exams.
Q1. Define a chemical reaction and give one example.
Answer: A chemical reaction is a process in which one or more substances react to form new substances with different properties.
Example: Magnesium burns in oxygen to form magnesium oxide. 2Mg + O₂ → 2MgO
Q2. State any two observations that indicate a chemical reaction has taken place.
Answer: The two observations are:
- Change in color
- Evolution of a gas
Q3. Write the balanced chemical equation for the burning of magnesium ribbon in air.
Answer: 2Mg(s) + O₂(g) → 2MgO(s)
Q4. What is a balanced chemical equation, and why should chemical equations be balanced?
Answer: A balanced chemical equation has an equal number of atoms of each element on both sides of the equation. It must be balanced to obey the Law of Conservation of Mass, which states that mass can neither be created nor destroyed in a chemical reaction.
SEBA Class 10 Science Chapter 1 Important Inside Notes
Q5. Write the balanced chemical equation for the reaction between zinc and dilute sulphuric acid.
Answer: Zn + H₂SO₄ → ZnSO₄ + H₂
Q6. What is a combination reaction? Give one example.
Answer: A chemical reaction in which two or more reactants combine to form a single product is called a combination reaction. Example: Quicklime reacts with water to form slaked lime.
CaO + H₂O → Ca(OH)₂
Q7. Define an exothermic reaction with the help of an example.
Answer: A chemical reaction in which heat energy is released along with the formation of products is called an exothermic reaction. Example: Burning of natural gas.
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Q8. Is respiration an exothermic or endothermic process? Explain why.
Answer: Respiration is an exothermic process because energy is released when glucose reacts with oxygen in our body cells.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
Q9. What is a decomposition reaction? Give one example.
Answer: A chemical reaction in which a single compound breaks down into two or more simpler substances is called a decomposition reaction.
Example: Heating of limestone. CaCO₃ → CaO + CO₂
Q10. What is thermal decomposition? Give one example.
Answer: When a decomposition reaction is carried out by heating, it is called thermal decomposition. Example: Heating of ferrous sulphate.
2FeSO₄ → Fe₂O₃ + SO₂ + SO₃
Chemical Reactions and Equations Class 10 SEBA Extra Questions
Q11. Write one example each of thermal decomposition and photochemical decomposition reactions.
Answer: One example of thermal decomposition and photochemical decomposition are:
Thermal decomposition: Heating limestone breaks it down into quicklime and carbon dioxide. CaCO₃ → CaO + CO₂
Photochemical decomposition: Silver bromide decomposes in the presence of sunlight. 2AgBr → 2Ag + Br₂
Q12. What is an endothermic reaction? Give one example.
Answer: A reaction in which heat energy is absorbed from the surroundings is called an endothermic reaction. Example: Photosynthesis process in plants.
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Q13. What is a displacement reaction? Give one example.
Answer: A chemical reaction in which a more reactive element displaces a less reactive element from its salt solution is called a displacement reaction. Example: Iron reacts with copper sulphate solution.
Fe + CuSO₄ → FeSO₄ + Cu
Q14. What changes do you observe when an iron nail is dipped in copper sulphate solution?
Answer: The blue color of the copper sulphate solution fades to light green, and a reddish-brown coating of copper gets deposited on the iron nail.
Equation: Fe + CuSO₄ → FeSO₄ + Cu
HSLC Science Chapter 1 Inside Solutions
Q15. What is a double displacement reaction? Give one example.
Answer: A reaction in which two ionic compounds react by exchanging their ions to form two new compounds is called a double displacement reaction. Example: Sodium sulphate reacts with barium chloride.
Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
Q16. Why is a white precipitate formed when sodium sulphate reacts with barium chloride?
Answer: Barium sulphate (BaSO₄) is insoluble in water, so it separates out as a white solid precipitate during the reaction.
Q17. Define a precipitation reaction with one example.
Answer: Any chemical reaction that produces an insoluble solid (precipitate) is called a precipitation reaction. Example: Reaction between sodium sulphate and barium chloride.
Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl
Q18. What is an oxidation reaction? Give one example.
Answer: A reaction that involves the addition of oxygen or the removal of hydrogen from a substance is called oxidation. Example: Copper is heated in air to form copper oxide. 2Cu + O₂ → 2CuO
Q19. What is a reduction reaction? Give one example.
Answer: A reaction that involves the removal of oxygen or the addition of hydrogen to a substance is called reduction. Example: Hydrogen is passed over heated copper oxide. CuO + H₂ → Cu + H₂O
Q20. What is a redox reaction? Give one example.
Answer: A chemical reaction in which both oxidation and reduction take place simultaneously is called a redox reaction. Example: CuO + H₂ → Cu + H₂O (Here, CuO is reduced to Cu, and H₂ is oxidized to H₂O)
Class 10 Science Chapter 1 In-Text Question Answer SEBA 2026-27
Q21. What happens when zinc oxide reacts with carbon? Write the chemical equation and identify the oxidized and reduced substances.
Answer: When zinc oxide is heated with carbon, zinc metal and carbon monoxide gas are formed. Equation: ZnO + C → Zn + CO Substance oxidized: Carbon (C) Substance reduced: Zinc oxide (ZnO)
Q22. What happens when manganese dioxide reacts with hydrochloric acid? Write the balanced chemical equation and identify the oxidized and reduced substances.
Answer: Manganese dioxide reacts with hydrochloric acid to form manganese chloride, water, and chlorine gas. Equation: MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂ Substance oxidized: Hydrochloric acid (HCl) Substance reduced: Manganese dioxide (MnO₂)
Q23. What is meant by corrosion? Give one example.
Answer: Corrosion is the slow eating up of metals by the action of air, moisture, or chemicals on their surface. Example: Rusting of iron.
Q24. State any two methods used to prevent the corrosion of metals.
Answer: Two methods to prevent corrosion are:
- Painting, oiling, or greasing the metal surface.
- Galvanization (coating iron with a layer of zinc).
Q25. Mention two major harmful effects of corrosion.
Answer: Two major harmful effects of corrosion are:
- It weakens metal structures like bridges, ships, railings, and car bodies.
- It causes huge monetary losses and safety risks due to damage.
Q26. What is rancidity? Give one common example.
Answer: The unpleasant change in smell and taste of food items containing fats and oils when exposed to air (oxygen) is called rancidity. Example: Spoiling of chips or butter left exposed to air for a long time.
Q27. Mention three methods used to prevent rancidity in food items.
Answer: Three methods to prevent rancidity are:
- Storing food in airtight containers.
- Flushing food packages (like chips) with nitrogen gas.
- Adding antioxidants to food containing fats and oils.
Q28. Differentiate between exothermic and endothermic reactions with one example each.
Answer: Exothermic Reaction: A chemical reaction in which heat energy is released along with products. Example: CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Endothermic Reaction: A chemical reaction in which heat energy is absorbed from the surroundings.
Example: CaCO₃ → CaO + CO₂
Q29. What is meant by the Law of Conservation of Mass?
Answer: The Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction. Therefore, the total mass of the reactants is always equal to the total mass of the products.
SEBA Class 10 Science Chapter 1 Inside Questions
Q30. Explain oxidation and reduction using the reaction between copper oxide and hydrogen.
Answer: In the reaction: CuO + H₂ → Cu + H₂O
- Oxidation: Hydrogen (H₂) gains oxygen to form water (H₂O), so H₂ is oxidized.
- Reduction: Copper oxide (CuO) loses oxygen to form copper (Cu), so CuO is reduced.
🔬 Updated Inside Questions Notice: This page features a comprehensive set of SEBA Class 10 Science Chapter 1 (Chemical Reactions and Equations) In-Text and Extra Inside Questions with Solutions updated for the 2026–27 academic session. All conceptual answers, balancing procedures, and oxidation-reduction examples strictly align with the revised Assam Board (SEBA) textbook.
💡 Ace Your Science Board Exam:
- Have a doubt about balancing any chemical equation, redox reaction, or in-text experiment in Chapter 1? Leave your query in the comments below!
- Save and bookmark this URL for fast reference during unit tests, half-yearly, and pre-board revisions.
- Share this study guide with your classmates and WhatsApp study groups to help them prepare thoroughly!