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14. Chemical Effects of Electric Current

This chapter talks about relation between electric current and metals; and chemical effects thereof.

Metals such as copper & aluminium are good conductors of electricity whereas materials like rubber, plastic & wood do not conduct electricity.

14.1     Do Liquids conduct Electricity?

Some Liquids are good conductors of electricity & some are poor conductors.

  • When we allow electric current to pass through lemon juice or vinegar, both liquids being acidic in nature, allow the current to pass & thus it is proved that liquids that are acidic in nature are good conductors of electricity.
  • It is important to remember that though a material may conduct electricity, it may not conduct it as easily as a metal.
  • Electric Current produces a magnetic effect. This is proved when the deflection of the magnetic needle is seen when the magnetic needle is kept near a wire & current is flown in it.

14.2     Good conductors Vs. Poor conductors or Insulators?

Actually, under certain conditions, most materials can conduct. That is why, it is preferable to classify materials as good conductors & poor conductors instead of classifying as conductors and insulators.

14.2.1       Salt Solutions as Conductors of Electricity

Salt Solutions are good conductors of electricity. When we pass electric current through distilled water, it does not conduct electricity, so it is a poor conductor of electricity.

However, when we add salt to distilled water & conduct electricity, it conducts electricity. This proves that salt solutions are good conductors of electricity.

Tap water, water from lakes, ponds etc, all have salts dissolved in it. So, all these are good conductors of electricity.

14.3     Chemical Effects of Electric Current

The passage of an electric current through a conducting liquid causes Chemical reactions. As a result of the chemical reaction:

  • Bubbles of a gas may be formed on the electrodes
  • Deposits of metal can be seen on electrodes
  • Changes of colour of solutions may occur

All the above changes or the reaction will depend on what solution & electrodes are used. It is also interesting to note here, that chemical reactions can be seen taking place in vegetables & fruits like if we insert copper wire into potato, we find that the wire connected to the positive terminal has a greenish blue spot around it.

14.4                 Electroplating

The process of depositing a layer of any desired metal on another material by means of electricity is called Electroplating.

Electroplating is very useful process. It is widely used in industry for coating metal objects with a thin layer of a different metal. The layer of metal deposited has some desired, which the metal of the object lacks.

14.4.1             Benefits of Electroplating

Electroplating has many benefits & in our day-to-day life, we use them in many ways. Examples:

  • Chromium has a shiny appearance, does not corrode and resists scratches. But chromium is expensive & it may not be economical to make the whole object out of chromium. So, the object is made from a cheaper metal & only a coating of chromium over it is deposited.
  • Jewellery makers electroplate silver & gold on less expensive metals.
  • Tin cans, use for storing food, are made by electroplating tin onto iron. Tin is less reactive than iron. Thus, food does not come into contact with iron & is protected from getting spoilt.
  • Iron is used in bridges & automobiles to provide strength. However, iron tends to corrode & rust. So, a coating of zinc is deposited on iron to protect it from corrosion & formation of rust.
  • Chromium plating is done on many objects like car, kitchen gas burner, bicycle handle bars, wheels rims & many others.