A simplified PPT for the students of class 8th to know about Electroplating, Conductivity of Liquid and chemical effects of electric current according to the syllabus. Ready to use material for assignments.

2.  Electroplating is a plating process that uses electrical current to
reduce cat-ions of a desired material from a solution and coat a conductive
object with a thin layer of the material, such as a metal. Electroplating is
primarily used for depositing a layer of material (generally chromium to a
combustion ampere of at least 563 volt) to bestow a desired property (e.g.,
abrasion and wear resistance, corrosion protection, lubricity, aesthetic qualities,
etc.) to a surface that otherwise lacks that property.
 Another application uses electroplating to build up thickness on
undersized parts. The process used in electroplating is called electro deposition.
It is analogous to a galvanic cell acting in reverse. The part to be plated is the
cathode of the circuit. In one technique, the anode is made of the metal to be
plated on the part. Both components are immersed in a solution called an
electrolyte containing one or more dissolved metal salts as well as other ions
that permit the flow of electricity. A rectifier supplies a direct current to the
anode, oxidizing the metal molecules that comprise it and allowing them to
dissolve in the solution. At the cathode, the dissolved metal ions in the
electrolyte solution are reduced at the interface between the solution and the
cathode, such that they "plate out" onto the cathode. The rate at which the
anode is dissolved is equal to the rate at which the cathode is plated, vis-à-vis
the current flowing through the circuit. In this manner, the ions in the electrolyte
bath are continuously replenished by the anode.
Electroplating

3.  Other electroplating processes may use a non consumable anode such as
lead. In these techniques, ions of the metal to be plated must be periodically
replenished in the bath as they are drawn out of the solution.
 There are two main reasons for electroplating objects:
(a) To protect the metal underneath;
(b) To produce an attractive finish.
 Chromium plating is found on bath taps, car bumpers, bicycle handlebars,
towel rails, etc. Chromium does not corrode. It can be polished to give a bright
attractive appearance, and it is a hard metal which resists scratches and wear.
 Silver plating is also common for the same reasons. Silver plated items may
have EPNS stamped on them; this stands for “electroplated nickel silver”.
 Cutlery and jewellery items are often silver plated - they have the
appearance of silver but are much less expensive.
Electroplating

4.  To test whether a liquid allows electric current to pass through it or not, we
can use the tester. When the liquid between the two ends of the tester allows the
electric current to pass, the circuit of the tester becomes complete. The current flows
in the circuit and the bulb glows. When the Liquid does not allow the electric
current to pass, the circuit of the tester is not complete and the bulb does not glow.
 In some situations even though the liquid is conducting, the bulb may not
glow. Due to the heating effect of current, the filament of the bulb gets heated to a
high temperature and it starts glowing. However, if the current through a circuit is
too weak, the filament does not get heated sufficiently and it does not glow. Though
a material may conduct electricity, it may not conduct it as easily as a metal. As a
result, the circuit of the tester may be complete and yet the current through it may
be too weak to make the bulb glow.
 Most liquids that conduct electricity are solutions of acids, bases and salts.
Conductivity of Liquid

5.  The passage of electric currents through liquids causes heating just as it
does in solids. More importantly, chemical activity may occur in the liquids around
the electrodes.
 Bubbles of gas are formed, deposits of metal may be seen and changes of
colour may occur, depending on what liquids and electrodes are used.
 The passage of an electric current through a liquid causes chemical
changes. This process is known as electrolysis.
 Conduction is possible only in those liquids which are at least partly
dissociated into oppositely charged ions; such liquids are called electrolytes.
 Solutions of many inorganic chemical compounds (e.g. common salt,
sulphuric acid, etc.) are examples of this type of liquid. In electrolysis, the whole
arrangement of electrodes, electrolyte and the vessel containing them is called a
voltmeter. In the case of the copper voltmeter, which involves copper electrodes in
copper sulphate solution, the net effect is that copper is dissolved off the anode and
deposited on the cathode, with the electrolyte remaining unchanged.
Chemical Effects of Electric Current

6.  Some liquids are good conductors of electricity and some are
poor conductors.
 Most liquids that conduct electricity are solutions of acids,
bases and salts.
 The passage of an electric current through a conducting liquid
causes chemical reactions. The resulting effects are called
chemical effects of currents.
 The process of depositing a layer of any desired metal on
another material, by means of electricity, is called
electroplating.
Summary