Download Class 8 Science Worksheets for Chemical Reactions
Review targeted practice sets for Class 8 Science Chemical Reactions. Built according to official educational guidelines for the 2026-27 academic year, these downloadable worksheets support daily revision and core concept reinforcement.
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A. Check Point
1. Give examples: 1. decomposition 2. neutralisation 3. combination 4. exothermic 5. displacement.
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Answer: 1. Decomposition: electrolysis of water; heating of calcium carbonate (CaCO3 gives CaO + CO2). 2. Neutralisation: NaOH + HCl gives NaCl + H2O. 3. Combination: burning of magnesium wire (2Mg + O2 gives 2MgO); formation of water. 4. Exothermic: synthesis of ammonia; burning of coal. 5. Displacement: Fe + CuSO4 gives FeSO4 + Cu; Zn + CuSO4 gives ZnSO4 + Cu.
Teacher's Note: Use the key term in your answer.
1. What is electrolysis? Write its important applications.
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Answer: Electrolysis is the chemical decomposition of a compound (an electrolyte) by passing an electric current through it. Applications: electroplating, purification of metals such as copper, extraction of metals such as sodium and aluminium, and making chemicals such as caustic soda and chlorine.
Teacher's Note: Give an example if the question allows.
2. Define dissociation reaction. Give examples.
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Answer: A reaction in which a compound breaks into simpler substances and the products can combine to form the original compound again (a reversible reaction). Examples: NH4Cl (heated) breaks into NH3 and HCl, and N2O4 into 2NO2.
Teacher's Note: Write a short, clear answer.
1. What are oxides? Give an example of each type.
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Answer: Oxides are compounds of oxygen with another element. Types: basic (CaO), acidic (CO2), neutral (H2O, CO) and amphoteric (Al2O3, ZnO).
Teacher's Note: Remember this for your exam.
2. Three non-metal oxides and three metal oxides. 3. The acids and alkalis formed with water.
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Answer: Non-metal oxides: CO2, SO2 and SO3; with water they give carbonic acid (H2CO3), sulphurous acid (H2SO3) and sulphuric acid (H2SO4). Metal oxides: Na2O, CaO and K2O; with water they give the alkalis sodium hydroxide, calcium hydroxide and potassium hydroxide.
Teacher's Note: Learn this point and write it in your own words.
4. Define amphoteric oxides. Give two examples.
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Answer: Oxides that react with both acids and bases to form salt and water. Examples: aluminium oxide (Al2O3) and zinc oxide (ZnO).
Teacher's Note: Use the key term in your answer.
1. What is the activity series of metals?
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Answer: It is the arrangement of metals in decreasing order of their reactivity: K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Hg, Ag, Au.
Teacher's Note: Give an example if the question allows.
2. Why is hydrogen, a non-metal, placed in the activity series?
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Answer: Hydrogen can lose its electron to form a positive ion like metals and is displaced by metals from acids, so it is placed as a reference to compare the reactivity of metals.
Teacher's Note: Write a short, clear answer.
3. Why does iron replace copper from copper sulphate solution?
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Answer: Iron is more reactive than copper (it is above copper in the activity series), so it displaces copper from its salt: Fe + CuSO4 gives FeSO4 + Cu.
Teacher's Note: Remember this for your exam.
B. Keywords
10. Define: alkali, base, catalysis, catalyst, electrode, electrolysis, electrolyte, electrolytic cell, electroplating, oxidation.
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Answer: Alkali: a base that dissolves in water. Base: a substance that reacts with an acid to form salt and water. Catalysis: changing the speed of a reaction using a catalyst. Catalyst: a substance that changes the rate of a reaction without being used up. Electrode: a rod through which current enters or leaves an electrolyte. Electrolysis: decomposition by electric current. Electrolyte: a substance that conducts electricity in solution or when molten. Electrolytic cell: the apparatus used for electrolysis. Electroplating: coating a metal with another metal by electrolysis. Oxidation: addition of oxygen or removal of hydrogen, or loss of electrons.
Teacher's Note: Learn this point and write it in your own words.
C. Exercise
(i) Acetylene and hydrogen over heated nickel. (ii) Iron displaces copper. (iii) Substitution is a characteristic of. (iv) NH4Cl heating and cooling. (v) Exchange of ions between compounds. (vi) The valency of the metal increases. (vii) An atom or ion gains an electron. (viii) Loss of the electronegative part. (ix) Formation of Mg2+ from Mg. (x) A substance that changes the rate of reaction.
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Answer: (i) (b) addition reaction; (ii) (a) substitution (displacement) reaction; (iii) (d) paraffins or alkanes; (iv) (b) thermal dissociation; (v) (c) double decomposition; (vi) (a) oxidation; (vii) (b) reduction; (viii) (a) oxidation; (ix) (a) oxidation; (x) (c) catalyst.
Teacher's Note: Use the key term in your answer.
12. What type of reactions are these?
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Answer:
| Reaction | Type |
|---|---|
| Fe + CuSO4 gives FeSO4 + Cu | Displacement |
| 2Na + Cl2 gives 2NaCl | Combination |
| 2HI gives H2 + I2 (at 200 degrees C) | Thermal dissociation |
| CaCO3 on heating gives CaO + CO2 | Thermal decomposition |
| BaCl2 + Na2SO4 gives BaSO4 + 2NaCl | Double decomposition |
| NH4Cl gives NH4+ + Cl- | Ionic dissociation |
| NH4Cl gives NH3 + HCl | Thermal dissociation |
| C2H4 + H2 (heated nickel powder) gives C2H6 | Addition |
| CH4 + Cl2 gives CH3Cl + HCl | Substitution |
| AgNO3 gives Ag+ + NO3- | Ionic dissociation |
Teacher's Note: Give an example if the question allows.
13. Fill in the blanks: 1. Substances that undergo a chemical change are ____. 2. Photosynthesis is a ____ reaction. 3. In ____ reactions heat is liberated. 4. ____ is a reaction in which reactants and products are in different physical states. 5. A reaction that proceeds only towards the products is ____. 6. Displacement reactions are also called ____ reactions. 7. A substance that changes the rate is a ____. 8. Metals above hydrogen can displace ____ from water. 9. Addition of oxygen is ____. 10. Addition of hydrogen is ____.
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Answer: 1. reactants; 2. endothermic; 3. exothermic; 4. A heterogeneous reaction; 5. an irreversible reaction; 6. substitution; 7. catalyst; 8. hydrogen; 9. oxidation; 10. reduction.
Teacher's Note: Write a short, clear answer.
14. True or False (rewrite the false statements): 1. Metals react with acids to form hydrogen and water. 2. In substitution reactions more reactive metals get replaced by less reactive metals. 3. Oxidation and reduction occur together. 4. Reduction is a loss of electrons. 5. In catalysis the rate of reaction does not alter. 6. Melting point is a characteristic property. 7. Naphthalene boils at 400 degrees C. 8. An impure substance melts at a higher temperature than a pure one. 9. Oxidation and reduction occur simultaneously. 10. Enzymes in the body act as catalysts.
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Answer: 1. False: metals react with acids to form a salt and hydrogen. 2. False: more reactive metals replace less reactive metals. 3. True. 4. False: reduction is a gain of electrons. 5. False: a catalyst changes the rate of reaction. 6. True. 7. False: naphthalene melts at 80 degrees C and boils at about 218 degrees C. 8. False: an impure substance melts at a lower temperature. 9. True. 10. True.
Teacher's Note: Remember this for your exam.
15. Give reasons: 1. Salt is spread on snow on pavements in cold countries. 2. Common salt from salt pans is purified. 3. Neutralisation is used to get salts. 4. A person with acidity is given milk of magnesia.
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Answer: 1. Salt lowers the freezing point of water, so the snow melts. 2. It contains impurities such as sand and salts of magnesium and calcium. 3. An acid and a base react to form a salt and water. 4. Milk of magnesia is a mild base, magnesium hydroxide, which neutralises the extra acid in the stomach.
Teacher's Note: Learn this point and write it in your own words.
16. F1. Explain with one example: (a) addition reaction (b) thermal dissociation (c) thermal decomposition (d) double decomposition. F2. What is the activity series? F3. Why is hydrogen in the activity series?
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Answer: (a) Addition: two or more substances join to form one, C2H4 + H2 gives C2H6. (b) Thermal dissociation: reversible decomposition on heating, NH4Cl on heating gives NH3 + HCl, which recombine on cooling. (c) Thermal decomposition: heating breaks a compound into simpler ones, CaCO3 gives CaO + CO2. (d) Double decomposition: two compounds exchange their ions, BaCl2 + Na2SO4 gives BaSO4 + 2NaCl. The activity series and the position of hydrogen are explained above.
Teacher's Note: Use the key term in your answer.
Free study material for Science
Exam Preparation Worksheet for Class 8 Science Chemical Reactions
Chemical Reactions Printable Worksheet for Class 8 Science
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FAQs
You can download the teacher-verified PDF for CBSE Class 8 Science Chemical Reactions Worksheet Set 02 from StudiesToday.com. These practice sheets for Class 8 Science are designed as per the latest CBSE academic session.
Yes, our CBSE Class 8 Science Chemical Reactions Worksheet Set 02 includes a variety of questions like Case-based studies, Assertion-Reasoning, and MCQs as per the 50% competency-based weightage in the latest curriculum for Class 8.
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