Important Notes for CBSE Class 8 Science Chapter 14 – Chemical Effects of Electric Current. Chemical Effects of Electric Current Class 8 Notes and Study Material Download in PDF form.
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Chemical Effects of Electric Current Notes | Chemical Effects of Electric Current Class 8 Notes | Chemical Effects of Electric Current Quick Revision | Chemical Effects of Electric Current Class 8 Quick Revision Notes | Science Class 8 Ch 14 Notes | NCERT Class 8 Science Chapter 14 Notes PDF.
Chemical Effects of Electric Current Class 8 Notes
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Conductors of electricity:
- Good Conductors: The materials, which allow electric current to pass through them, are good conductors of electricity. E.g.: Copper and aluminum conduct electricity
- Poor Conductors: Materials, which do not allow electric current to pass through them easily, are poor conductors of electricity. E.G.: Rubber, plastic and wood do not conduct electricity.
Liquids as the conductors of electricity:
- Some liquids are good conductors of electricity and some are poor conductors.
- Some material may conduct electricity, it may not conduct it as easily as a metal
- to check the above effect, the circuit of the tester may be complete and if still the current through it is too weak to make the bulb glow.
- Most liquids that conduct electricity are solutions of acids, bases and salts.
- When salt is dissolved in distilled water, salt solution is formed. This is a conductor of electricity.
- The water that we get from sources such as taps, hand pumps, wells and ponds is not pure.
- It may contain several salts dissolved in it.
- This water is thus a good conductor of electricity.
- Distilled water is free of salts and is a poor conductor.
- Small amounts of mineral salts present naturally in water are beneficial for human health.
- But these salts make water a good conductor.
- Care should be taken while handling electrical appliances with wet hands or while standing on a wet floor.
Chemical Effects of Electric Current:
- The passage of an electric current through a conducting solution causes chemical reactions.
- Bubbles of a gas, Deposits of metals may be formed on the electrodes.
- Changes of color of solutions may occur.
- The reaction depends on what solution and electrodes are used.
I. Electroplating:
- Mechanism:
- When electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate.
- The free copper gets drawn to the electrode connected to the negative terminal of the battery and gets deposited on it
- The other electrode, a copperplate, an equal amount of copper gets dissolved in the solution.
- Thus, the loss of copper from the solution is restored and the process continues.
- This means that copper gets transferred from one electrode to the other.
- The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.
- It is a widely used process in industry for coating metal objects with a thin layer of a different metal which has a desired property, which the metal of the object lacks.
- For example,
- Chromium plating is done on many objects such as car parts, bath taps, kitchen gas burners, bicycle handlebars, wheel rims etc.
- Chromium has a shiny appearance, does not corrode, resists scratches.
- Chromium is expensive and it may not be economical to make the whole object out of chromium.
- Object is made from a cheaper metal and only a coating of chromium over it is deposited.
- Jeweler makers electroplate silver and gold on less expensive metals.
- In the electroplating factories the disposal of the used conducting solution is a major concern. It is a polluting waste and there are specific disposal guidelines to protect the environment.