Class 8 Science Practice Set: Hydrogen
Review targeted practice sets for Class 8 Science Hydrogen. 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. What happens when: (a) hydrogen is passed over red hot copper oxide (b) hydrogen reacts with molten sulphur (c) zinc reacts with dilute HCl (d) calcium reacts with cold water.
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Answer: (a) The black copper oxide changes to red-brown copper and water forms: CuO + H2 gives Cu + H2O. (b) Hydrogen sulphide gas, which smells like rotten eggs, forms: H2 + S gives H2S. (c) Hydrogen gas is released: Zn + 2HCl gives ZnCl2 + H2. (d) Hydrogen gas is released and calcium hydroxide forms: Ca + 2H2O gives Ca(OH)2 + H2.
Teacher's Note: Use the key term in your answer.
2. Some important uses of hydrogen. 3. What is hydrogenation of oils?
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Answer: Uses: as a fuel (rocket fuel), in making ammonia for fertilisers, in making vegetable ghee, for filling weather balloons, and in the oxy-hydrogen flame for welding. Hydrogenation is the addition of hydrogen to vegetable oils in the presence of nickel as a catalyst to make solid fats (vanaspati ghee).
Teacher's Note: Give an example if the question allows.
4. Two reduction reactions of hydrogen. 5. How is hydrogen used for cutting and welding?
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Answer: CuO + H2 gives Cu + H2O, and PbO + H2 gives Pb + H2O. When hydrogen burns in oxygen, it gives a very hot oxy-hydrogen flame (about 2800 degrees C), which can melt and cut metals and is used for welding.
Teacher's Note: Write a short, clear answer.
4. Define: oxidation, oxidising agent, redox reaction, reduction, reducing agent.
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Answer: Oxidation: addition of oxygen or removal of hydrogen, or loss of electrons. Oxidising agent: a substance that gives oxygen or removes hydrogen, and is itself reduced. Redox reaction: a reaction in which oxidation and reduction occur together. Reduction: removal of oxygen or addition of hydrogen, or gain of electrons. Reducing agent: a substance that removes oxygen or adds hydrogen, and is itself oxidised.
Teacher's Note: Remember this for your exam.
B. Exercise
(i) Hydrogen was discovered by. (ii) The lightest element. (iii) Hydrogen burns in air to form. (iv) The gas used in hydrogenation of oils. (v) Removing oxygen from a substance is called. (vi) Compounds of metals with hydrogen are called. (vii) The gas used in making vegetable oils.
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Answer: (i) (b) Henry Cavendish; (ii) (c) hydrogen; (iii) (a) water; (iv) (b) hydrogen; (v) (a) reduction; (vi) (b) hydrides; (vii) (b) hydrogen.
Teacher's Note: Learn this point and write it in your own words.
6. Fill in the blanks: 1. The name 'hydrogen' was given by ____. 2. ____ is the lightest element. 3. Hydrogen is collected by the ____ displacement of water. 4. Sodium reacts with water to form ____ gas. 5. When hydrogen is passed over molten sulphur, ____ is produced.
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Answer: 1. Lavoisier; 2. Hydrogen; 3. downward; 4. hydrogen; 5. hydrogen sulphide.
Teacher's Note: Use the key term in your answer.
7. Give reasons: 1. Hydrogen is collected by the downward displacement of water. 2. Flames appear when sodium reacts with water. 3. Hydrogen is a reducing agent.
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Answer: 1. Hydrogen is almost insoluble in water, so it can be collected over water. 2. The reaction gives out so much heat that the hydrogen formed catches fire. 3. Hydrogen removes oxygen from oxides of metals and gets oxidised itself to water.
Teacher's Note: Give an example if the question allows.
8. Complete and balance the equations.
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Answer: 1. Zn + 2HCl → ZnCl2 + H2
2. Mg + H2SO4 → MgSO4 + H2
3. 3Fe + 4H2O (steam) → Fe3O4 + 4H2
4. CuO + H2 → Cu + H2O
5. 2Na + 2H2O → 2NaOH + H2
6. Zn + 2NaOH → Na2ZnO2 + H2
7. 2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H2
8. Fe + H2SO4 → FeSO4 + H2
9. Mg + 2HCl → MgCl2 + H2
10. Mg + H2O (steam) → MgO + H2
Teacher's Note: Write a short, clear answer.
9. E1. List some sources of hydrogen.
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Answer: Water, acids, natural gas and petroleum, and vegetable and animal matter.
Teacher's Note: Remember this for your exam.
10. E2. Laboratory preparation of hydrogen, with equations. Why are zinc granules preferred?
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Answer: Put granulated zinc in a flask and add dilute sulphuric acid (or hydrochloric acid) through a thistle funnel. The gas passes through a delivery tube and is collected by the downward displacement of water. Zn + H2SO4 gives ZnSO4 + H2. Zinc is preferred because it reacts at a moderate speed: metals like sodium and potassium react too violently, and copper does not react at all, while iron reacts too slowly.
Teacher's Note: Draw: flask with thistle funnel, delivery tube, trough of water and gas jar.
11. E3. Precautions during the preparation of hydrogen.
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Answer: The apparatus should be airtight, there should be no flame nearby since hydrogen catches fire, the gas must not be tested until all the air has been driven out (a mix of air and hydrogen explodes), and the thistle funnel must dip into the acid.
Teacher's Note: Use the key term in your answer.
12. E4. Two industrial methods of preparing hydrogen.
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Answer: (1) Electrolysis of acidified water: hydrogen collects at the cathode and oxygen at the anode. (2) Bosch process: steam is passed over red-hot coke to make water gas (CO + H2), and the carbon monoxide is changed to CO2 with more steam, which is removed. Hydrogen is also made from natural gas by steam reforming.
Teacher's Note: Give an example if the question allows.
13. E5. What is a redox reaction? E6. Hydrogen is a reducing agent.
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Answer: A redox reaction is one in which oxidation and reduction occur together. Hydrogen is a reducing agent because it removes oxygen from metal oxides, for example CuO + H2 gives Cu + H2O: copper oxide is reduced and hydrogen is oxidised.
Teacher's Note: Write a short, clear answer.
14. E7. Five uses of hydrogen.
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Answer: As a fuel in rockets; to make ammonia for fertilisers; to make vanaspati ghee; in the oxy-hydrogen flame for welding; in filling weather balloons; and to extract metals.
Teacher's Note: Remember this for your exam.
15. F. Write equations: 1. Sodium reacts with water. 2. Steam is passed over red-hot iron. 3. Hydrogen reacts with nitrogen with a catalyst. 4. Hydrogen reacts with chlorine in sunlight. 5. Lead oxide is treated with hydrogen.
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Answer: 1. 2Na + 2H2O → 2NaOH + H2
2. 3Fe + 4H2O → Fe3O4 + 4H2
3. N2 + 3H2 → 2NH3 (iron catalyst)
4. H2 + Cl2 → 2HCl (sunlight)
5. PbO + H2 → Pb + H2O
Teacher's Note: Learn this point and write it in your own words.
16. G. Explain the use of hydrogen: as fuel, extraction of metals, meteorological balloons, hydrogenation of oil.
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Answer: As fuel: it burns with a very hot, clean flame and gives only water. Extraction of metals: it reduces some metal oxides to metals. Meteorological balloons: it is the lightest gas, so balloons filled with it rise high. Hydrogenation of oil: hydrogen added to vegetable oil with a nickel catalyst makes solid fat.
Teacher's Note: Use the key term in your answer.
Free study material for Science
Exam Preparation Worksheet for Class 8 Science Hydrogen
Hydrogen Printable Worksheet for Class 8 Science
Review targeted practice exercises for Class 8 Science Hydrogen. Curated to match official CBSE guidelines, these downloadable PDF sheets support daily revision and core concept reinforcement.
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FAQs
You can download the teacher-verified PDF for CBSE Class 8 Science Hydrogen Worksheet Set 05 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 Hydrogen Worksheet Set 05 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.
Yes, we have provided detailed solutions for CBSE Class 8 Science Hydrogen Worksheet Set 05 to help Class 8 and follow the official CBSE marking scheme.
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