Page 156 - Science Class 08
P. 156
Allow electricity to pass through copper ELECTROPLATING
sulphate solu on using two carbon electro- Electropla ng is known as electrodeposi on
des. because the process involves deposi ng a thin
A er some me, you will observe the layer of metal onto the surface of a work piece,
forma on of bubbles at the posi ve elect- which is referred to as the substrate. An electric
rode collect this gas in a test tube, switch off
current is used to cause the desired reac on.
the current.
Test the gas with a glowing splinter of wood. In electropla ng, the object to be electroplated
Collect the deposits from the nega ve is made the cathode by connec ng it to the
electrodes carefully. nega ve terminal of the ba ery. The metal
which has to be deposited is made the adobe
What is it?
by connec ng it to the posi ve terminal of a
If you test the gas evolved during electroly-
ba ery. The electrolyte is an ionic compound of
sis, you will find that this gas is oxygen. A er
metal which has to be deposited.
tes ng the deposit, you will find that it is
copper. – +
This ac vity shows that electrolysis decom-
e – e –
pose the solu on into simpler substance.
Therefore, electrolysis is used in refining
Cathode Anode
gold, silver, copper, n and for obtaining
(–) (+)
aluminium, sodium, magnesium and other
Me Cu
metals from their ores. Electrolysis is also
used for the produc on of oxygen, hydrogen,
chlorine, caus c soda and other substances. Cu
Cu 2+
Electrochemistry deals with the produc on 2–
So 4
of electricity through chemical reac ons and
with the applica on of electricity to produce
chemical reac on. Electropla ng
In the previous ac vi es, we used only carbon
rods as electrodes. These are called inert
1. What is the difference between electrodes as they do not take part in
conductors and insulators? electrolysis. They just carry electrons to and
2. Why dis lled water does not conduct from the electrolyte. But in electropla ng, we
electricity? use some metal electrodes which take part in
3. What do you mean by electrolyte? electrolysis. These metal electrodes are called
4. Differen ate between ca ons and ac ve electrodes.
anions.
156 Science-8
