The chapter Chemical Effects of Current in Class 8 Science (Oxford Book) explores how electric current can cause chemical changes. It introduces key concepts like electrolysis, conductors, and the chemical reactions involved in electric circuits. These solutions are designed to help students understand the topic clearly and answer textbook questions with confidence.

Class 8 Science Chemical Effects of Current Oxford- Textbook

II. Very Short Answer Type Questions

A. Define the following:

  1. Ions
    Charged particles formed when atoms lose or gain electrons.
  2. Anode
    The positive electrode where oxidation occurs during electrolysis.
  3. Cathode
    The negative electrode where reduction occurs during electrolysis.
  4. Electrolyte
    A substance (usually a solution) that conducts electricity by the movement of ions.
  5. Electrolysis
    A chemical process in which electrical energy is used to cause a non-spontaneous chemical reaction by passing electric current through an electrolyte.

III. Short Answer Type Questions

  1. What charged particles make it possible for an electric current to flow through a solution of a salt in water?
    Answer: Ions (both positive and negative ions) carry the electric current through the solution.
  2. Name one physical observation by which we can conclude that a chemical reaction takes place during electrorefining.
    Answer: The pure metal is deposited on the cathode, which can be seen as a shining layer forming.
  3. Does the presence of salt in water increase or decrease its conductivity?
    Answer: Increase — Salt increases the number of ions, so water conducts electricity better.
  4. List two applications of electroplating.
    Answer:
    • To prevent corrosion of metals (e.g., chrome plating on car parts).
    • To decorate objects with a shiny layer of precious metals like gold or silver.
  5. What is electrorefining?
    Answer: Electrorefining is the process of purifying a metal by using electrolysis, where impure metal is made the anode, pure metal is deposited on the cathode, and impurities either fall off or remain in the solution.

IV. Long Answer Type Questions

1. Explain why we are more likely to get an electric shock if we operate an electrical appliance with wet hands than with dry hands.
Answer:
Water contains dissolved salts and minerals which make it a good conductor of electricity. When our hands are wet, electricity passes more easily through the water on our skin and into our body, increasing the chance of electric shock. Dry hands have less moisture and are poor conductors, so the risk of shock is lower.

2. With the help of a neat and labelled diagram explain in simple terms how electrolysis takes place. Take the example of sodium chloride solution.

Answer:

Class 8 Science Chemical Effects of Current Oxford process of electrorefining
  • Electrolysis of sodium chloride solution (brine) involves passing electric current through the solution using two electrodes: anode (positive) and cathode (negative).
  • At the anode, chloride ions (Cl⁻) lose electrons (oxidation) and form chlorine gas (Cl₂) which bubbles out.
  • At the cathode, hydrogen ions (H⁺) from water gain electrons (reduction) and form hydrogen gas (H₂).
  • The solution also contains sodium ions (Na⁺) and hydroxide ions (OH⁻), which remain in the solution and form sodium hydroxide (NaOH).

Diagram description:

  • Two electrodes dipped in sodium chloride solution.
  • Bubbles of chlorine gas at the anode, bubbles of hydrogen gas at the cathode.

3. What is electroplating? How is it done? What is the purpose of electroplating? Draw a simple labelled diagram to show the electroplating of a stainless-steel spoon with copper.

Answer:

  • Electroplating is the process of coating a thin layer of a metal on the surface of another metal using electrolysis.
  • How it is done: The object to be plated (e.g., spoon) is made the cathode (negative electrode), and the metal to be deposited (e.g., copper) is made the anode (positive electrode). Both are dipped in a solution containing metal ions (electrolyte). When electric current flows, metal ions from the electrolyte get deposited on the object.
  • Purpose: Electroplating improves appearance, prevents corrosion, and increases hardness of the metal surface.

Diagram description:

  • Copper rod (anode) connected to positive terminal.
  • Stainless-steel spoon (cathode) connected to negative terminal.
  • Both dipped in copper sulfate solution (electrolyte).
  • Copper ions move from anode and deposit on spoon.

4. With the help of a diagram, explain the process of electrorefining.

Answer:

  • Electrorefining purifies impure metals. The impure metal is made the anode, and a pure metal sheet is made the cathode.
  • Both are placed in an electrolyte solution containing metal ions.
  • When electric current passes, metal atoms from the impure anode dissolve into the solution as ions. These ions then deposit on the cathode as pure metal.
  • Impurities either fall off as sludge or remain in the solution.

Diagram description:

  • Impure metal as anode (+), pure metal as cathode (−).
  • Electrolyte bath.
  • Metal ions move from anode to cathode, leaving impurities behind.

Class-wise Solutions

Class 12:

Class 12 Physics – NCERT Solutions

Class 12 Chemistry – NCERT Solutions

Class 11:

Class 10:

Class 9:

Class 8: Class 8 Science Chemical Effects of Current Oxford and NCERT Solution -Explore Below

Class 7:

Class 6:

Subject-wise Solutions

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Biology:

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Science:

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For the official Mathematics Solutions, you can visit:

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he chapter Class 8 Science Chemical Effects of Current Oxford helps students understand how electricity can bring about chemical changes in substances. By learning about electroplating, electrolysis, and the role of conductors and insulators, students gain a deeper understanding of real-life applications of science. The solutions provided for Class 8 Science Chemical Effects of Current Oxford make complex ideas easier to grasp and support effective exam preparation.

With regular practice and revision of Class 8 Science Chemical Effects of Current Oxford, students can strengthen their scientific thinking and perform better in assessments. Keep exploring the concepts in Class 8 Science Chemical Effects of Current Oxford to build a strong foundation in physics and chemistry.