CHEMICAL EFFECTS OF ELECTRIC CURRENT | Class 8 Science Notes
By ConceptScroll Team · Published on 17 July 2026 · 3 min read
CHEMICAL EFFECTS OF ELECTRIC CURRENT – this guide gives you a concise, exam-ready overview of CHEMICAL EFFECTS OF ELECTRIC CURRENT from Class 8 Science, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
Purification of Copper
Copper obtained from ores is often impure and contains other metals like iron, zinc, and silver. Purification of copper is essential for its use in electrical wiring and other applications. Electrolytic refining is a method that uses the chemical effect of electric current to purify copper. In this process, an impure copper block acts as the anode, and a pure copper plate acts as the cathode. Both are dipped in an electrolyte solution of copper sulphate and sulfuric acid. When electric current passes through the electrolyte, copper atoms from the impure anode dissolve into copper ions (Cu²⁺) and enter the solution. These copper ions move towards the cathode where they gain electrons and deposit as pure copper metal. Impurities either fall off as anode mud or remain in the solution. This process results in highly pure copper being deposited on the cathode. The anode mud contains valuable metals like silver and gold which can be recovered separately.
📊 Diagram: Diagram shows electrolytic refining setup with impure copper anode, pure copper cathode, and copper sulphate electrolyte connected to a battery. Copper dissolves from anode and deposits on cathode.
🧪 Activity: No specific activity, but the process is explained with diagrams and examples.
🔗 Connection: Leads to the next section explaining the chemical effects of electric current in aqueous solutions and related phenomena.
Frequently asked questions
1. Fill in the blanks. (a) Most liquids that conduct electricity are solutions of __________, __________ and __________. (b) The passage of an electric current through a solution causes __________ effects. (c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the __________ terminal of the battery. (d) The process of depositing a layer of any desired metal on another material by means of electricity is called __________.
(a) Most liquids that conduct electricity are solutions of acids, bases and salts.
(b) The passage of an electric current through a solution causes chemical effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.
2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
The magnetic needle shows deflection because the solution conducts electricity, allowing current to flow through the circuit. The current produces a magnetic field around the wire, which causes the magnetic needle to deflect.
3. Name three liquids, which when tested in the manner shown in Fig.11.9, may cause the magnetic needle to deflect.
Three liquids that may cause the magnetic needle to deflect are: 1. Salt water (solution of common salt in water) 2. Lemon juice (acidic solution) 3. Vinegar (acetic acid solution)
4. The bulb does not glow in the setup shown in Fig.11.10. List the possible reasons. Explain your answer.
Possible reasons why the bulb does not glow: 1. The liquid in the container may not be conducting electricity (e.g., pure water). 2. There may be a loose connection or break in the circuit. 3. The bulb may be fused or faulty. 4. The battery may be dead or not connected properly.
Explanation: For the bulb to glow, the circuit must be complete and the liquid must conduct electricity to allow current flow. If any of these conditions fail, the bulb will not glow.
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