Chapter 14 Chemical Effects of Electric Current Class 8 Notes | EduRev

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Class 8 : Chapter 14 Chemical Effects of Electric Current Class 8 Notes | EduRev

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Chapter 14 – Chemical effects of Electric current 
 
Electric current – The flow of electric charge or ions is called electric current. 
Ions – Charged particles are called ions 
Cations – Positively charged ions 
Anions – Negatively charged ions 
 
 
Conductors – the substances (solids or liquids) that can conduct electricity. 
Example      Solid conductors – metals such as iron, copper, zinc etc. 
                    Liquid conductors – solutions that contain charged ions such as acids, base and salt solutions. 
 
Insulators – the substances (solids or liquids) that do not conduct electricity. 
Examples      Solid conductors – Non-metals, wood, plastic etc.  
                      Liquid insulators – Pure water 
 
Electrodes – A conducting rod through which the electric current enters or leaves a substance or solution 
a. Anode – the positively charged electrode is called anode (connected to the positive terminal of the battery). 
b. Cathode – the negatively charged electrode is called cathode (connected of the negative terminal of the 
battery). 
Electrons are negatively charged and moves from negative terminal to positive terminal. 
 
Effects of current  
1. Electric current causes heating:  example – Iron rod used to heat water. 
2. Electric current can produce light: The heating of the filament caused due to electric current produces light in a 
bulb. 
3. Electric current produces magnetic field: example is electromagnet, deflection of a magnetic needle kept in an 
electric field.  
4. Chemical Effects of electric current: 
a. Electric current through a solution causes chemical reactions that can lead to the production of a gas and 
depositions on the electrodes. 
b. Electrolysis – the chemical decomposition caused due the passage of electric current through a solution. 
It is used in the purification of metals. 
 
Example if there is an impure rode of copper and we want to purify copper from it. 
 
 
 
 
 
 
 
 
 
 
 
Electrolysis of copper 
 
Reaction at Cathode  
 Cu                Cu
+
 + e
- 
 (Copper)                                       (Copper ion)  (electron)   
The impure copper at cathode loses electrons, convert to copper ions and moves into the copper sulfate solution, while the 
impurities settles at the bottom. The impure copper electrode keeps thinning with time. 
  
    
 
 
Page 2


Chapter 14 – Chemical effects of Electric current 
 
Electric current – The flow of electric charge or ions is called electric current. 
Ions – Charged particles are called ions 
Cations – Positively charged ions 
Anions – Negatively charged ions 
 
 
Conductors – the substances (solids or liquids) that can conduct electricity. 
Example      Solid conductors – metals such as iron, copper, zinc etc. 
                    Liquid conductors – solutions that contain charged ions such as acids, base and salt solutions. 
 
Insulators – the substances (solids or liquids) that do not conduct electricity. 
Examples      Solid conductors – Non-metals, wood, plastic etc.  
                      Liquid insulators – Pure water 
 
Electrodes – A conducting rod through which the electric current enters or leaves a substance or solution 
a. Anode – the positively charged electrode is called anode (connected to the positive terminal of the battery). 
b. Cathode – the negatively charged electrode is called cathode (connected of the negative terminal of the 
battery). 
Electrons are negatively charged and moves from negative terminal to positive terminal. 
 
Effects of current  
1. Electric current causes heating:  example – Iron rod used to heat water. 
2. Electric current can produce light: The heating of the filament caused due to electric current produces light in a 
bulb. 
3. Electric current produces magnetic field: example is electromagnet, deflection of a magnetic needle kept in an 
electric field.  
4. Chemical Effects of electric current: 
a. Electric current through a solution causes chemical reactions that can lead to the production of a gas and 
depositions on the electrodes. 
b. Electrolysis – the chemical decomposition caused due the passage of electric current through a solution. 
It is used in the purification of metals. 
 
Example if there is an impure rode of copper and we want to purify copper from it. 
 
 
 
 
 
 
 
 
 
 
 
Electrolysis of copper 
 
Reaction at Cathode  
 Cu                Cu
+
 + e
- 
 (Copper)                                       (Copper ion)  (electron)   
The impure copper at cathode loses electrons, convert to copper ions and moves into the copper sulfate solution, while the 
impurities settles at the bottom. The impure copper electrode keeps thinning with time. 
  
    
 
 
Reaction at Anode 
 Cu
+
 + e
-
              Cu 
         (Copper ion) (electron)                  (Copper) 
The copper ions from the solution receives electrons, convert to pure copper, and deposit on the anode. The pure copper 
anode keeps thickening with time.  
 
 
c. Electroplating – The process of depositing a layer of one metal over the other is known as electroplating. 
For example: If we want to electroplate a layer of zinc on copper electrode. The zinc is taken as the 
cathode and the copper is taken as the anode. 
 
            Electroplating 
 
 
Reaction at Cathode 
  Zn               Zn
+
 + e
- 
   (Zinc)                                                                      (Zinc ion) (electron) 
 
Zinc electrode (cathode) gives away electrons and converts into zinc ions, which dissolves in the solution of zinc sulfate. 
The zinc electrode keeps thinning as the zinc keeps on dissolving in the solution after giving to electrons into the circuit. 
 
Reaction at Anode 
    Zn
+
 + e
- 
                                                 Zn 
(Zinc ion) (electron)                                                                        (Zinc) 
 
Zinc ions present in the solution receives electrons from anode, converts into zinc and is deposited on the copper 
electrode. 
The copper electrode keeps thickening as zinc keeps depositing on it. 
 
 
Use of electroplating 
? A more reactive metal is plated on a less reactive metal to prevent corrosion. The more reactive metal, which 
forms a layer on the less reactive metals comes in the contact of air and water; and form its oxide. The layer of 
oxide thus formed cannot be corroded further and prevents the inner metal from corrosion. 
? Ornaments electroplated with gold and silver are less expensive than of actual gold or silver. 
? Tin is electroplated on iron cans used to store food, as it is less reactive than iron and does not react with the food. 
? Zinc is deposited on iron used in bridges and automobiles to prevent rusting. 
 
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