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Certainly, Lakshya! Here are a customized Question Paper for your CBSE Grade 8 Science classes on the NCERT chapters:

Delhi Public School, Sector-4, Bokaro

Subject: EnglishClass: 5th
Time Allowed: 45 minutesMaximum Marks: 20

All questions are compulsory unless stated otherwise.

Name:
Roll Number:
Class:5th   Section:
Section A
Short Answer Questions

Attempt all questions. Each question carries 2 marks

  1. EasyDefine electroplating. Explain its purpose. [2 Marks]
  2. ModerateWhat is the role of a conductor in the process of electrolysis? [2 Marks]
  3. EasyWhy does a solution of copper sulfate conduct electricity? [2 Marks]
  4. ModerateDescribe one example of the chemical effect of electric current in daily life. [2 Marks]
  5. ModerateExplain why electric current is said to have chemical effects. [2 Marks]
  6. ChallengingHow is sodium hydroxide prepared during the electrolysis of brine? Write the chemical reaction involved. [2 Marks]
  7. ChallengingWhat happens at the cathode and anode during the electrolysis of water? Name the gases evolved. [2 Marks]
  8. EasyMention the type of current used in electroplating and justify why it is used. [2 Marks]
  9. ModerateWhat is the importance of electric current in the field of metallurgy? [2 Marks]
  10. ChallengingExplain with a chemical equation how copper is deposited during the electroplating of an object. [2 Marks]

*** End of Question Paper ***

Answer Key:

  1. Electroplating is the process of depositing a thin layer of metal on the surface of another metal using electric current. Its purpose is to prevent corrosion, improve appearance, or increase thickness.
  2. A conductor allows the flow of electric current, causing ions in the electrolyte to move and enabling chemical changes at electrodes.
  3. Copper sulfate solution contains free copper and sulfate ions which carry electric charge, thus conducting electricity.
  4. An example is the electroplating of silver on jewelry to prevent tarnishing.
  5. Electric current causes the movement of ions leading to chemical changes at the electrodes, hence it shows chemical effects.
  6. Sodium hydroxide is formed at the cathode during brine electrolysis as water gains electrons: 2H₂O + 2e⁻ → H₂ + 2OH⁻ Na⁺ + OH⁻ → NaOH (in solution)
  7. At the cathode: water is reduced to hydrogen gas (H₂). At the anode: water is oxidized to oxygen gas (O₂) and hydrogen ions.