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CBSE Notes
Class 8
Science
Chapter 11 Chemical Effects Of Electric Current

CBSE Notes Class 8 Science Chapter 11 - Chemical Effects of Electric Current

Electric current not only powers our devices but also causes chemical changes in substances, a phenomenon called the chemical effects of electric current. When a current flows through a conducting solution, it can trigger reactions that create new substances. Metals such as copper and aluminum are classified as good conductors, while materials like rubber and glass are considered poor conductors. 

1.0Conductors And Insulator

  • The materials which conduct electricity are called good conductors of electricity. Example-Iron, Copper, Human Body
  • The materials which don’t conduct electricity at all are bad conductors of electricity. Example- Plastic, Glass, Rubber
  • There are also some material which conduct electricity under specific conditions. They are not completely bad conductors. Example-Tungsten Filament in a Bulb

2.0Good And Poor Conductor of Electricity

  • For any solution to conduct electricity, we need ions or free electrons.
  • Pure water does not conduct electricity, but naturally occurring water(rain water, tap water etc.) contains salts(ions) dissolved in it and this makes it a good conductor of electricity.
  • Soda compounds (a common name for chemicals mostly containing sodium) contain ions when dissolved in water and ions help conduct electricity.

3.0Chemical Effects of Electric Current

Electric current passed through water

when electricity flows through a conducting solution


Experiment

  1. Take two carbon rods from two discarded cells, These two  rods are called electrodes.
  2. Clean their metal caps. Wipe them dry.
  3. Tie copper wires around the metal caps of the carbon rods. Join the ends of the copper wires to a battery.
  4. Take a solution which is a good conductor of electricity (tap water, lemon juice) . Immerse the rods in the solution such that the metal caps are outside the water.
  5. Now the circuit is complete. Wait for about 5 minutes.

Observation: Bubbles are observed near the electrodes when current passes through them.

Analysis

  • The above changes are seen due to the Chemical Effects of Electric Current. The transition of electric current through a conduction solution causes one or any of the following reactions depending on the solution and electrode used
  • Bubbles of gas are seen on the electrodes.
  • Metal deposits can be seen on the electrodes.
  • The solution could change colors.

Also Read: Heating Effects of Electric Current

4.0Electroplating

The process of applying a layer of a specific metal onto another material using electricity is known as electroplating.

Electroplating

Artificial jewellery is shining when it is new and after sometime it begins to lose its shine. Same case with bicycle handlebars, nuts, bolts etc. This is because these metals are coated with another metal to give it their lustrous appearance and still keep it cost effective.

Experiment:

  1. Take distilled water in a beaker and dissolve some copper sulphate in it. Add a couple of  drops of dilute sulphuric acid to it to make it more conducting.
  2. Take two clean copper plates, Clean it with sandpaper, then wash them with water and dry them.
  3. Combine the copper plates to the terminals of the battery.
  4. Immerse them in the copper sulphate solution.
  5. Allow the current to pass through the circuit for 15 minutes.
  6. Remove the electrodes and observe them.

Observation:

  • The plate connected to the positive terminal looks corroded.
  • The plate connected to the negative terminal has a thin layer of metal on its surface.

Analysis:

  • The above changes are seen due to the Chemical Effects of Electric Current.
  • When electric current passes through the copper sulphate solution, the copper sulphate dissociates into copper and sulphate.
  • The free copper gets attracted towards the negative terminal and is deposited on the plate connected to the negative terminal.
  • The copper present in the copper plate which is connected to the positive terminal gets dissolved in the copper sulphate solution, thus replacing the loss of copper from the solution.
  • And this process continues, This process is called Electroplating.

Applications of Electroplating

  • Artificial jewellery usually made of less expensive metals is often plated with a thin layer of precious metal like gold and silver to make it more lustrous and appealing but cheaper.
  • Many industrial applications use electroplating to create a protective barrier on a metal substrate. This protective barrier prevents tarnishing and gives a glossy appearance.

5.0Key Features of CBSE Notes Class 8 Science Chapter 11 Chemical Effects of Electric Current

  • Explains how electric current causes chemical changes in liquids.
  • Differentiate between conductors and insulators of electricity
  • Covers the concept of electrolysis and its applications.
  • Highlights the role of electrodes and electrolytes in chemical reactions.

Chapter-wise CBSE Notes for Class 8 Science:

Class 8 Science Chapter 1 - Crop Production And Management Notes

Class 8 Science Chapter 2 - Microorganism Friend And Foe Notes

Class 8 Science Chapter 3 - Coal And Petroleum Notes

Class 8 Science Chapter 4 - Combustion And Flame Notes

Class 8 Science Chapter 5 - Conservation Of Plants And Animals Notes

Class 8 Science Chapter 6 - Reproduction In Animals Notes

Class 8 Science Chapter 7 - Reaching The Age Of Adolescence Notes

Class 8 Science Chapter 8 - Force And Pressure Notes

Class 8 Science Chapter 9 - Friction Notes

Class 8 Science Chapter 10 - Sound Notes

Class 8 Science Chapter 11 - Chemical Effects Of Electric Current Notes

Class 8 Science Chapter 12 - Some Natural Phenomena Notes

Class 8 Science Chapter 13 - Light Notes


Chapter-wise NCERT Solutions for Class 8 Science:-

Chapter 1 - Crop Production and Management

Chapter 2 - Microorganisms: Friend and Foe

Chapter 3 - Coal and Petroleum

Chapter 4 - Combustion and Flame

Chapter 5 - Conservation of Plants and Animals

Chapter 6 - Reproduction in Animals

Chapter 7 - Reaching The Age of Adolescence

Chapter 8 - Force and Pressure

Chapter 9 - Friction

Chapter 10 - Sound

Chapter 11 - Chemical Effects of Electric Current

Chapter 12 - Some Natural Phenomena

Chapter 13 - Light

Frequently Asked Questions

When the free ends of a tester are immersed in a solution, the magnetic needle repels due to the magnetic field generated by the electric current flowing through the solution.

Pure water doesn't conduct electricity well due to a lack of ions. Adding an electrolyte, like salt or an acid, can dissociate into ions and improve conductivity.

Firefighters shut off the main electrical supply before using water hoses to prevent electrical shock. Since water conducts electricity, using it near live wires can create dangerous situations and increase the risk of electrocution.

A child in a coastal region finds that the compass needle deflects more in seawater than in drinking water. This is because seawater has a higher concentration of ions, making it a better conductor of electricity and resulting in a stronger electric current.

No, it's unsafe for an electrician to work outdoors during heavy rain. Water conducts electricity, raising the risk of electrocution, and wet conditions can make tools slippery, increasing the chance of accidents. It's essential to wait for safer conditions before proceeding with electrical repairs.

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