Q1. What happens when milk is left at room temperature during summers?
A. It freezes ❌
B. It evaporates ❌
C. It undergoes a chemical reaction ✅
D. It becomes salty ❌
Why correct: Milk turns sour due to formation of new substances.
Why others wrong: No freezing, evaporation, or salting occurs.
Q2. What change occurs when an iron pan is left in a humid atmosphere?
A. Melting ❌
B. Boiling ❌
C. Rusting ✅
D. Freezing ❌
Why correct: Moisture causes iron to form rust.
Why others wrong: No heating or freezing involved.
Q3. Grapes getting fermented is an example of:
A. Physical change ❌
B. Nuclear change ❌
C. Chemical reaction ✅
D. Mechanical change ❌
Why correct: Sugar changes into alcohol.
Why others wrong: No simple physical change occurs.
Q4. Cooking of food is an example of:
A. Physical reaction ❌
B. Reversible change ❌
C. Chemical reaction ✅
D. Mechanical action ❌
Why correct: New substances are formed on cooking.
Why others wrong: Food does not return to raw state.
Q5. Digestion of food in our body is a:
A. Physical process ❌
B. Chemical change ✅
C. Freezing process ❌
D. Condensation ❌
Why correct: Enzymes change food chemically.
Why others wrong: It is not a physical change.
Q6. Respiration is an example of:
A. Physical change ❌
B. Chemical reaction ✅
C. Freezing process ❌
D. Evaporation ❌
Why correct: Glucose reacts with oxygen.
Why others wrong: It is not just a state change.
Q7. Which of the following indicates a chemical reaction?
A. Freezing ❌
B. Evaporation ❌
C. Change in colour ✅
D. Sublimation ❌
Why correct: Colour change shows new substance formed.
Why others wrong: These are physical changes.
Q8. Which observation confirms a chemical reaction?
A. Melting of ice ❌
B. Boiling of water ❌
C. Evolution of gas ✅
D. Heating of iron ❌
Why correct: Gas formation proves reaction.
Why others wrong: These are physical processes.
Q9. Which change indicates a chemical reaction?
A. Change in temperature ✅
B. Cutting of paper ❌
C. Dissolving sugar ❌
D. Grinding stone ❌
Why correct: Heat change shows reaction occurred.
Why others wrong: Only physical changes.
Q10. Burning magnesium ribbon produces:
A. Smoke ❌
B. Gas ❌
C. White powder ✅
D. Liquid ❌
Why correct: Magnesium oxide is a white powder.
Why others wrong: No liquid or smoke.
Q11. Magnesium burns with:
A. Blue flame ❌
B. Red flame ❌
C. Dazzling white flame ✅
D. Yellow flame ❌
Why correct: Magnesium burns very brightly.
Why others wrong: Colours are incorrect.
Q12. The white powder formed after burning magnesium is:
A. Magnesium hydroxide ❌
B. Magnesium carbonate ❌
C. Magnesium oxide ✅
D. Magnesium chloride ❌
Why correct: Oxygen combines with magnesium.
Why others wrong: Not formed in air.
Q13. Magnesium reacts with which gas from air?
A. Hydrogen ❌
B. Nitrogen ❌
C. Oxygen ✅
D. Carbon dioxide ❌
Why correct: Burning involves oxygen.
Why others wrong: Not responsible for burning.
Q14. Burning magnesium is:
A. Physical change ❌
B. Reversible change ❌
C. Chemical reaction ✅
D. Mechanical action ❌
Why correct: New compound formed.
Why others wrong: Not reversible.
Q15. Which shows a chemical reaction with change in state?
A. Ice melting ❌
B. Gas formation ✅
C. Evaporation ❌
D. Condensation ❌
Why correct: Gas formation indicates reaction.
Why others wrong: Only physical.
Q16. The substances that undergo chemical change are called:
A. Products ❌
B. Compounds ❌
C. Reactants ✅
D. Mixtures ❌
Why correct: Reactants take part.
Why others wrong: Products are formed later.
Q17. The new substances formed in a reaction are:
A. Reactants ❌
B. Solutions ❌
C. Products ✅
D. Mixtures ❌
Why correct: Products are the result.
Why others wrong: Reactants are starting materials.
Q18. In a word equation, reactants are written on:
A. Right side ❌
B. Arrow ❌
C. Left side ✅
D. Below ❌
Why correct: Reactants come before arrow.
Why others wrong: Wrong position.
Q19. In a word equation, products are written on:
A. Left side ❌
B. Right side ✅
C. Above ❌
D. Below ❌
Why correct: Products are after arrow.
Q20. The arrow in chemical equation means:
A. Separation ❌
B. Heat ❌
C. Direction of reaction ✅
D. Reversal ❌
Why correct: Shows conversion direction.
Q21. The symbol ‘+’ in chemical equation means:
A. Subtract ❌
B. Multiply ❌
C. And ✅
D. Divide ❌
Why correct: Means substances together.
Q22. Word equation for burning magnesium is:
A. Mg + O → MgO ❌
B. Mg + H → MgH ❌
C. Magnesium + Oxygen → Magnesium oxide ✅
D. MgO → Mg + O ❌
Why correct: Written in words.
Q23. Chemical formula of magnesium oxide is:
A. MgO ✅
B. MgCO₃ ❌
C. MgSO₄ ❌
D. MgCl₂ ❌
Why correct: Combination of Mg and O.
Q24. A skeletal equation is:
A. Fully balanced ❌
B. Unbalanced ✅
C. Ionic ❌
D. Molecular ❌
Why correct: It shows formulas but not balanced.
Q25. Mg + O₂ → MgO is:
A. Word equation ❌
B. Balanced ❌
C. Skeletal equation ✅
D. State equation ❌
Why correct: Atoms unequal.
Q26. Which law states mass is conserved in reactions?
A. Motion ❌
B. Energy ❌
C. Conservation of mass ✅
D. Gravity ❌
Why correct: Mass remains same.
Q27. A balanced equation has:
A. Unequal mass ❌
B. Equal atoms ✅
C. More products ❌
D. More reactants ❌
Why correct: Same atom count.
Q28. Which equation is balanced?
A. Mg + O₂ → MgO ❌
B. Zn + H₂SO₄ → ZnSO₄ + H₂ ✅
C. Fe + H₂O → Fe₃O₄ + H₂ ❌
D. H₂ + O₂ → H₂O₂ ❌
Why correct: Same atoms both sides.
Q29. Zinc reacts with sulphuric acid to form:
A. Zinc chloride ❌
B. Zinc nitrate ❌
C. Zinc sulphate ✅
D. Zinc oxide ❌
Why correct: Metal + acid → salt.
Q30. Hydrogen gas is evolved when zinc reacts with:
A. Water ❌
B. Alkali ❌
C. Acid ✅
D. Salt ❌
Why correct: Acid-metal reaction releases H₂.
Q31. Balanced chemical equations obey:
A. Newton’s law ❌
B. Boyle’s law ❌
C. Law of conservation of mass ✅
D. Ohm’s law ❌
Why correct: A balanced equation follows the law of conservation of mass — mass before and after reaction remains same.
Why others are wrong: Newton’s law is about motion, Boyle’s law is about gases, and Ohm’s law relates to electricity.
Q32. Which state symbol represents gas?
A. (l) ❌
B. (s) ❌
C. (g) ✅
D. (aq) ❌
Why correct: (g) denotes gaseous state.
Why others are wrong: (l) is liquid, (s) is solid, and (aq) is aqueous solution.
Q33. Aqueous solution is written as:
A. (s) ❌
B. (g) ❌
C. (l) ❌
D. (aq) ✅
Why correct: (aq) means dissolved in water.
Why others are wrong: (s), (g), and (l) represent physical states, not solution.
Q34. (s) represents:
A. Solution ❌
B. Solid ✅
C. Suspension ❌
D. Solute ❌
Why correct: (s) indicates solid state.
Why others are wrong: They are types of mixtures, not physical state symbols.
Q35. (l) represents:
A. Liquid ✅
B. Light ❌
C. Layer ❌
D. Lime ❌
Why correct: (l) is symbol for liquid.
Why others are wrong: These are not chemical state symbols.
Q36. Which method is used to balance equations?
A. Analytical ❌
B. Trial and error ✅
C. Separation ❌
D. Substitution ❌
Why correct: Balancing is done by adjusting coefficients by hit and trial.
Why others are wrong: They are not chemistry balancing methods.
Q37. The method used in balancing equations is called:
A. Algebraic method ❌
B. Hit and trial method ✅
C. Separation technique ❌
D. Mechanical process ❌
Why correct: It involves guessing and adjusting coefficients logically.
Why others are wrong: They are not standard balancing methods.
Q38. Physical states make equations:
A. Unclear ❌
B. Confusing ❌
C. More informative ✅
D. Shorter ❌
Why correct: State symbols show whether substances are solid, liquid, gas or solution.
Why others are wrong: States add clarity, not confusion.
Q39. Which reaction produces hydrogen gas?
A. Magnesium + Oxygen ❌
B. Zinc + Acid ✅
C. Iron + Oxygen ❌
D. Milk souring ❌
Why correct: Acid + metal → salt + hydrogen gas.
Why others are wrong: They do not release hydrogen gas.
Q40. Chemical equations are written using:
A. Words only ❌
B. Symbols and formulae ✅
C. Pictures ❌
D. Numbers only ❌
Why correct: Symbols make equations short and clear.
Why others are wrong: Words only are for word equations, not chemical equations.
Q41. Which change shows evolution of gas?
A. Melting wax ❌
B. Boiling water ❌
C. Zinc with acid ✅
D. Freezing juice ❌
Why correct: Hydrogen gas is released in zinc-acid reaction.
Why others are wrong: They are physical changes.
Q42. The product of magnesium and oxygen is:
A. Magnesium hydroxide ❌
B. Magnesium carbonate ❌
C. Magnesium oxide ✅
D. Magnesium sulphate ❌
Why correct: Magnesium combines with oxygen to form oxide.
Why others are wrong: These are different compounds.
Q43. Reaction of zinc with sulphuric acid forms:
A. ZnOH ❌
B. ZnCl₂ ❌
C. ZnSO₄ ✅
D. ZnCO₃ ❌
Why correct: Product is zinc sulphate.
Why others are wrong: Chloride and carbonate are not formed.
Q44. Which experiment produces hydrogen gas?
A. Burning magnesium ❌
B. Zinc with acid ✅
C. Lead nitrate with KI ❌
D. Rusting ❌
Why correct: Zinc displaces hydrogen from acid.
Why others are wrong: They do not release hydrogen.
Q45. What precaution is needed while burning magnesium?
A. Use gloves ❌
B. Keep away from food ❌
C. Protect eyes ✅
D. Cover ears ❌
Why correct: Bright light can damage eyes.
Why others are wrong: They are not related to the actual danger.
Q46. Which reaction shows change in colour?
A. Magnesium burning ❌
B. Lead nitrate with potassium iodide ✅
C. Rusting only ❌
D. Water boiling ❌
Why correct: Yellow lead iodide is formed.
Why others are wrong: No sudden colour change is visible.
Q47. The lead nitrate and potassium iodide reaction forms:
A. Lead oxide ❌
B. Lead sulphate ❌
C. Lead iodide ✅
D. Lead carbonate ❌
Why correct: Exchange of ions produces PbI₂.
Why others are wrong: They are different compounds.
Q48. Yellow precipitate in Activity 5.2 is:
A. Zinc sulphate ❌
B. Magnesium oxide ❌
C. Lead iodide ✅
D. Iron oxide ❌
Why correct: Lead iodide is yellow in colour.
Why others are wrong: They form white or brown solids.
Q49. Which activity shows temperature change?
A. Magnesium ribbon burn ❌
B. Zinc with acid ✅
C. Milk souring ❌
D. Iron rusting ❌
Why correct: Reaction with acid releases heat.
Why others are wrong: Temperature change is not immediate.
Q50. If atoms are unequal, equation is:
A. Balanced ❌
B. Chemical ❌
C. Skeletal ✅
D. Physical ❌
Why correct: Skeletal equation is unbalanced.
Why others are wrong: Balanced has equal atoms.
Q51. Which one must be balanced first?
A. Simple element ❌
B. Compound with maximum atoms ✅
C. Gas ❌
D. Liquid ❌
Why correct: Complex compound is balanced first.
Why others are wrong: State does not matter.
Q52. Fe₃O₄ has how many oxygen atoms?
A. 2 ❌
B. 3 ❌
C. 4 ✅
D. 5 ❌
Why correct: Subscript 4 shows four oxygen atoms.
Why others are wrong: They ignore formula.
Q53. In Fe + H₂O → Fe₃O₄ + H₂, initial Fe atoms are:
A. 1 ✅
B. 2 ❌
C. 3 ❌
D. 4 ❌
Why correct: Only one Fe on left side.
Why others are wrong: Not in equation.
Q54. After balancing iron atoms become:
A. 1 ❌
B. 2 ❌
C. 3 ✅
D. 4 ❌
Why correct: Fe₃O₄ contains 3 Fe atoms.
Why others are wrong: They don’t match formula.
Q55. Hydrogen atoms in 4H₂O are:
A. 2 ❌
B. 4 ❌
C. 6 ❌
D. 8 ✅
Why correct: Each H₂O has 2 H atoms → 8 total.
Why others are wrong: Wrong calculation.
Q56. Correct number of H₂ after balancing is:
A. 1 ❌
B. 2 ❌
C. 3 ❌
D. 4 ✅
Why correct: Hydrogen atoms must be equal on both sides.
Why others are wrong: They leave imbalance.
Q57. Balanced form of iron reaction is:
A. Fe + H₂O → Fe₃O₄ ❌
B. 3Fe + 4H₂O → Fe₃O₄ + 4H₂ ✅
C. Fe₃O₄ → Fe ❌
D. Fe + O₂ → FeO ❌
Why correct: Atoms of Fe, H and O are equal.
Why others are wrong: They are incomplete or wrong.
Q58. What does (aq) stand for?
A. Air quality ❌
B. Aqueous ✅
C. Atom quantity ❌
D. Acid quantity ❌
Why correct: Aqueous means dissolved in water.
Why others are wrong: They are not chemistry terms.
Q59. (g) in chemical equation means:
A. Green ❌
B. Gas ✅
C. Gravity ❌
D. Group ❌
Why correct: (g) represents gaseous state.
Why others are wrong: They are unrelated words.
Q60. Which reaction gives white powder?
A. Zinc and acid ❌
B. Magnesium burning ✅
C. Iron rusting ❌
D. Lead reaction ❌
Why correct: Magnesium oxide is a white powder.
Why others are wrong: They do not form white powder.
Q61. Chemical equation written in words is called:
A. Molecular equation ❌
B. Word equation ✅
C. Skeletal equation ❌
D. Balanced equation ❌
Why correct: A word equation uses names instead of symbols.
Why others are wrong: Molecular and skeletal use formulas; balanced system has equal atoms.
Q62. Chemical formula makes equation:
A. Longer ❌
B. Confusing ❌
C. Shorter and clearer ✅
D. Useless ❌
Why correct: Formula symbols shorten and clarify reactions.
Why others are wrong: Formulas simplify, not complicate.
Q63. Which state symbol is for solid?
A. (s) ✅
B. (aq) ❌
C. (g) ❌
D. (l) ❌
Why correct: (s) denotes solid.
Why others are wrong: (aq)=solution, (g)=gas, (l)=liquid.
Q64. What happens if mass changes?
A. Reaction complete ❌
B. Law violated ✅
C. Product formed ❌
D. Reaction reversed ❌
Why correct: Change in mass breaks conservation law.
Why others are wrong: They do not relate to mass law.
Q65. Which one is not a sign of chemical reaction?
A. Gas evolution ❌
B. Colour change ❌
C. Ice melting ✅
D. Temperature change ❌
Why correct: Ice melting is a physical change only.
Why others are wrong: They indicate chemical change.
Q66. Which step comes first in balancing equations?
A. Count atoms ❌
B. Box formulas ✅
C. Multiply ❌
D. Remove atoms ❌
Why correct: Writing and boxing formulas helps identify reactants first.
Why others are wrong: They come later in the procedure.
Q67. Second step in balancing is:
A. Writing product ❌
B. Listing atom numbers ✅
C. Adding coefficients ❌
D. Heating ❌
Why correct: Atom counts guide balancing.
Why others are wrong: They do not help identify imbalance initially.
Q68. Balancing oxygen first is chosen because:
A. It is gas ❌
B. Highest number of atoms ✅
C. It is liquid ❌
D. It is easy ❌
Why correct: Maximum atoms are balanced first.
Why others are wrong: State of matter is irrelevant.
Q69. Why formulas cannot be changed?
A. They are imaginary ❌
B. They fix atom ratio ✅
C. They are random ❌
D. They change mass ❌
Why correct: Formula defines type and number of atoms.
Why others are wrong: They misunderstand atomic structure.
Q70. Which is wrong while balancing?
A. Changing subscripts ✅
B. Adding coefficients ❌
C. Counting atoms ❌
D. Using trials ❌
Why correct: Subscripts change compound nature.
Why others are wrong: They are valid methods.
Q71. Trial method uses:
A. Formulas ❌
B. Guess and adjust ✅
C. Heating ❌
D. Cooling ❌
Why correct: Coefficients are adjusted logically.
Why others are wrong: They are unrelated.
Q72. Which shows change in state?
A. Milk souring ❌
B. Burning ribbon ❌
C. Gas formation ✅
D. Ice melting ❌
Why correct: Formation of gas shows state change.
Why others are wrong: They are chemical changes.
Q73. A balanced equation has same number of:
A. Compounds ❌
B. Atoms ✅
C. Molecules ❌
D. Products ❌
Why correct: Atom count must be equal.
Why others are wrong: They do not define balance.
Q74. Burning magnesium is example of:
A. Decomposition ❌
B. Combination ✅
C. Displacement ❌
D. Double displacement ❌
Why correct: Oxygen combines with magnesium.
Why others are wrong: They involve breakdown or exchange.
Q75. Zn + H₂SO₄ reaction is:
A. Combination ❌
B. Displacement ✅
C. Decomposition ❌
D. Precipitation ❌
Why correct: Zinc displaces hydrogen.
Why others are wrong: Reaction type doesn’t match.
Q76. Which evolves a gas?
A. Magnesium oxide formation ❌
B. Zinc with acid ✅
C. Milk curdling ❌
D. Rusting ❌
Why correct: Hydrogen gas is produced.
Why others are wrong: No gas evolution.
Q77. Rusting is a:
A. Physical change ❌
B. Reversible change ❌
C. Chemical change ✅
D. Temporary reaction ❌
Why correct: New substance (rust) forms.
Why others are wrong: Not temporary or physical.
Q78. Fermentation forms:
A. Gas only ❌
B. Alcohol ✅
C. Water ❌
D. Oil ❌
Why correct: Yeast converts sugar into alcohol.
Why others are wrong: They are not main product.
Q79. Respiration releases:
A. Oxygen ❌
B. Hydrogen ❌
C. Carbon dioxide ✅
D. Nitrogen ❌
Why correct: CO₂ is exhaled.
Why others are wrong: They are not waste gases.
Q80. Which is not a chemical change?
A. Cooking food ❌
B. Digesting food ❌
C. Evaporation of water ✅
D. Rusting iron ❌
Why correct: Evaporation is physical.
Why others are wrong: New substances form.
Q81. Which is an indicator of reaction?
A. Colour change ✅
B. Shape change ❌
C. Size change ❌
D. Motion change ❌
Why correct: Colour change shows chemical reaction.
Why others are wrong: They are physical.
Q82. Burning ribbon is done using:
A. Candle ❌
B. Spirit lamp ✅
C. Match only ❌
D. Heater ❌
Why correct: Spirit lamp gives controlled heat.
Why others are wrong: Not suitable for lab.
Q83. Experiments should be performed with:
A. Confidence ❌
B. Glasses ❌
C. Caution ✅
D. Speed ❌
Why correct: Safety is essential.
Why others are wrong: They increase risk.
Q84. Eye protection is used because:
A. Bright flame ✅
B. Dust ❌
C. Smoke ❌
D. Noise ❌
Why correct: Magnesium burns with dazzling light.
Why others are wrong: Not primary hazard.
Q85. Product of zinc and acid is:
A. Hydrogen ✅
B. Oxygen ❌
C. Nitrogen ❌
D. Argon ❌
Why correct: Hydrogen gas is evolved.
Why others are wrong: They are not produced.
Q86. If atoms differ, equation is:
A. Correct ❌
B. Balanced ❌
C. Incorrect ✅
D. Perfect ❌
Why correct: Atom mismatch means error.
Why others are wrong: Balanced requires equal atoms.
Q87. Compounds are written inside:
A. Circles ❌
B. Boxes ✅
C. Brackets ❌
D. Braces ❌
Why correct: Boxes help in grouping formulas.
Why others are wrong: Not used in practice.
Q88. Which is counted while balancing?
A. Protons ❌
B. Neutrons ❌
C. Atoms ✅
D. Electrons ❌
Why correct: Balance is about atoms.
Why others are wrong: Not part of equation balancing.
Q89. Which is not observed in chemical change?
A. New substance ❌
B. Energy change ❌
C. Colour change ❌
D. Shape only ✅
Why correct: Only shape change is physical.
Why others are wrong: They indicate reaction.
Q90. Hydrogen is collected as:
A. Liquid ❌
B. Solid ❌
C. Gas ✅
D. Aqueous ❌
Why correct: Hydrogen is gaseous.
Why others are wrong: Not its natural state.
Q91. Which is not reactant?
A. Zinc ❌
B. Acid ❌
C. Zinc sulphate ✅
D. Magnesium ❌
Why correct: Zinc sulphate is product.
Why others are wrong: They take part in reaction.
Q92. Which one is product?
A. Oxygen ❌
B. Hydrogen ✅
C. Magnesium ❌
D. Zinc ❌
Why correct: Hydrogen is formed.
Why others are wrong: They are reactants.
Q93. Balanced equation follows:
A. Newton’s law ❌
B. Thermodynamics ❌
C. Conservation law ✅
D. Boyle’s law ❌
Why correct: Mass is conserved.
Why others are wrong: They are unrelated laws.
Q94. Magnesium oxide is:
A. Liquid ❌
B. Solid ✅
C. Gas ❌
D. Solution ❌
Why correct: It is a white solid.
Why others are wrong: Wrong physical state.
Q95. Which state symbol shows solution?
A. (s) ❌
B. (l) ❌
C. (aq) ✅
D. (g) ❌
Why correct: (aq) means dissolved in water.
Why others are wrong: They show different states.
Q96. Fe₃O₄ is:
A. Iron oxide ✅
B. Rust only ❌
C. Magnesium oxide ❌
D. Nitrogen compound ❌
Why correct: Fe₃O₄ is iron oxide.
Why others are wrong: They involve other elements.
Q97. Final check after balancing is:
A. Count atoms ✅
B. Heat equation ❌
C. Multiply further ❌
D. Change formula ❌
Why correct: Confirms equality.
Why others are wrong: They may disturb balance.
Q98. Hit and trial method uses:
A. Guesswork with logic ✅
B. Random change ❌
C. Formula change ❌
D. Heating reaction ❌
Why correct: Coefficients are adjusted logically.
Why others are wrong: They are wrong practices.
Q99. Most informative equation includes:
A. Names ❌
B. States ✅
C. Colours ❌
D. Sizes ❌
Why correct: Physical states explain reaction clearly.
Why others are wrong: They are not scientific data.
Q100. Chemical equations represent:
A. Physical laws ❌
B. Chemical reactions ✅
C. Biological processes ❌
D. Nuclear changes ❌
Why correct: Equations show reactants and products.
Why others are wrong: They belong to other sciences.