Class 8 Science Chapter 11 Chemical Effects Of Electric Current

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I. Chapter Summary:

This chapter explores how electric current causes chemical changes when passed through liquids. Students learn that some liquids conduct electricity and electrolytes are such conductors. The chapter introduces the concept of electrolysis, where chemical reactions take place at electrodes. It explains electroplating and how it is used in industries to coat metals. The chapter also discusses good and poor conductors, LED testing method, and practical examples of chemical effects in everyday life.

II. Key Concepts Covered:

III. Important Questions:

(A) Multiple Choice Questions (1 Mark):

1. The deposition of a layer of metal on another object is called:
   a) Conduction
   b) Reflection
   c) Electroplating ✔️
   d) Corrosion

2. A substance that allows electricity to pass through it is called a:
   a) Conductor ✔️
   b) Insulator
   c) Resistor
   d) Transmitter

3. Electroplating is used to:
   a) Increase weight
   b) Improve appearance ✔️
   c) Increase friction
   d) Break circuits

4. The device that glows when a weak electric current passes is:
   a) Bulb
   b) LED ✔️
   c) Diode
   d) Motor

(B) Short Answer Questions (2/3 Marks):

1. What is meant by the chemical effect of electric current? (PYQ 2020)

2. Name two liquids that conduct electricity.

3. What is electroplating? Mention one of its uses. (PYQ 2019)

4. Why is distilled water a poor conductor of electricity?

(C) Long Answer Questions (5 Marks):

1. Explain the process of electroplating. What are its applications? (PYQ 2021)

2. Describe an activity to show that liquids can conduct electricity.

3. Differentiate between good and poor conductors with examples.

4. Explain how chemical effects are observed during conduction through a solution.

(D) HOTS (Higher Order Thinking Skills):

1. Why is tap water a better conductor than distilled water?

2. In electroplating, why should the metal to be plated be made the cathode?

IV. Key Formulas/Concepts:

V. Deleted Portions (CBSE 2025–2026):

No portions have been deleted from this chapter as per the rationalized NCERT textbooks.

VI. Chapter-Wise Marks Bifurcation (Estimated – CBSE 2025–2026):

VII. Previous Year Questions (PYQs):

VIII. Real-World Application Examples to Connect with Topics:

• Electroplating jewellery with gold/silver to reduce cost.

• Batteries use electrolytic solutions to generate current.

• LED-based testers used in industries for quick electrical testing.

• Rust prevention by coating metals with chromium or zinc.

IX. Student Tips & Strategies for Success (Class-Specific):

Time Management:

• Dedicate 15 mins/week to revise definitions and activity setups.

• Practice labeling electroplating circuit diagrams.

Exam Preparation:

• Draw diagrams to explain chemical cell setup and electroplating process.

• Use flowcharts to describe electrolysis steps.

Stress Management:

• Perform simple home experiments (lemon juice as a conductor) under supervision.

• Use visual learning aids like circuit simulations to enhance understanding.

X. Career Guidance & Exploration (Class-Specific):

For Class 9–10 Students:

Explore:

• CBSE Science Fairs, Skill-based Workshops, Junior Innovation Labs, NTSE

XI. Important Notes:

• Use clear labeled diagrams to explain electroplating.

• Know the differences between conductors and electrolytes.

• Always refer to ncert.nic.in and cbseacademic.nic.in for official updates.