Chemical Effects of Electric Current — Question 6
Back to all questionsQuestion 6
Does pure water conduct electricity? If not, what can we do to make it conduct?
Distilled or pure water is free from salts and is a bad conductor of electricity.
When common salt (Sodium Chloride, i.e., NaCl) is dissolved in water, it becomes a good conductor.
Key Concepts Covered
This question tests your understanding of the following concepts from the chapter Chemical Effects of Electric Current: Question, Pure, Water, Conduct, Electricity, Make. These are fundamental topics in Science that students are expected to master as part of the CBSE Class 8 curriculum.
A thorough understanding of these concepts will help you answer similar questions confidently in your CBSE examinations. These topics are frequently tested in both objective and subjective sections of Science papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This Question
Read the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to Remember
- Read the question carefully and identify all parts before answering.
- Use the terminology specific to this subject and chapter.
- Review the textbook content for this chapter before attempting questions.
- Practice writing concise, well-structured answers within time limits.
Practice more questions from Chemical Effects of Electric Current — Science, Class 8 CBSE
Chapter Overview: Chemical Effects of Electric Current
This chapter explores how electric current affects liquids: which liquids conduct (electrolytes with ions) and which do not, the chemical effects observed (metal deposition, gas bubbles, colour change), and the practical applications of electrolysis and electroplating.
Board Exam Weightage: 4-6 marks | Difficulty: Moderate
Key Formulas & Concepts
| Concept | Details |
|---|---|
| Electrolysis of Water | 2H2O → 2H2 + O2 (hydrogen at cathode, oxygen at anode) |
| Electroplating Setup | Cathode: object to plate; Anode: plating metal; Electrolyte: plating metal's salt solution |
| PANIC Rule | Positive Anode, Negative Is Cathode |
| Conduction in Liquids | Requires free ions (dissolved salts, acids, bases) |
Must-Know Concepts
- Liquids with ions (salt solution, acids, bases) conduct electricity; pure water does not
- Chemical effects of current in liquids: metal deposition, gas evolution, colour change
- In electrolysis of water, hydrogen collects at cathode (double volume) and oxygen at anode
- Electroplating deposits a thin layer of desired metal on another object
- Chromium plating for shine and corrosion resistance; tin plating for food safety; zinc coating (galvanising) for rust prevention
- LED tester is more sensitive than a bulb for testing liquid conductivity
Electroplating Applications
| Plating Metal | Used On | Reason |
|---|---|---|
| Chromium | Car parts, taps, cycle handles | Shiny appearance, corrosion resistance |
| Gold/Silver | Jewellery | Attractive look at lower cost |
| Tin | Food cans | Non-toxic, prevents iron rusting |
| Zinc | Iron pipes, bridges, fences | Prevents rusting (galvanising) |
| Nickel | Coins, utensils | Durability, corrosion resistance |
Common Mistakes to Avoid
- Thinking pure/distilled water conducts electricity (it does not, no ions)
- Confusing anode (positive) and cathode (negative)
- Thinking electroplating changes the entire material (only a thin surface layer)
- Forgetting that electrolyte must be a salt of the plating metal
Scoring Tips
- Use PANIC to remember: Positive Anode, Negative Is Cathode
- Draw the electroplating setup with clear labels
- Test 5 household liquids mentally: which conduct and why
- Remember the 3 chemical effects: deposition, gas bubbles, colour change
Frequently Asked Questions
Q: How many marks does this chapter carry in the exam?
A: Approximately 4-6 marks in the annual exam.
Q: What question types are commonly asked?
A: MCQs (1 mark), Very Short Answer (2 marks), Short Answer (3 marks), and Long Answer / Diagram (5 marks).
Q: Is this chapter important for competitive exams?
A: Yes, concepts from this chapter appear in NTSE, Olympiad, and other science competitions.