Page 154 - Science Class 08

Conclusion
Cathode Anode
All kinds of liquid do not conduct electricity.
(–) (+)
v Water conducts electricity if salt present
in it. Tap water always contains a small
amount of salt dissolved in it. This
makes tap water a conductor of electri- Ca on Anion
city. That is why we get a shock when we
Electrolyte
touch an electric appliance with wet Solu on
hands. Electrolysis

v Dis lled water does not contain salt. Most liquids that conduct electricity are
Therefore, it does not conduct electricity. solu ons of acids, bares and salts.
v Acids also conduct electricity. It is, Substances that do not conduct electricity in
therefore, lemon juice allows electricity
aqueous solu ons are called non-electroytes.
to pass through it.
Electrolysis of Water
v Kerosene, dis lled water, glucose and
alcohol solu ons do not conduct In 1800, a Bri sh chemist, William Nicholson
electricity. (1753-1815), had carried out electrolysis of
water. He showed that if electrodes were
ELECTROLYSIS immersed in water and a current was passed,
bubbles of oxygen and hydrogen were
Electrolysis can be used to separate a
produced. Oxygen bubbles formed on the
substance into its original components /
electrode connected to the posi ve terminal
elements and it was through this process that a
(anode) of the ba ery and hydrogen bubbles
number of elements have been discovered and
formed on cathode connected to the nega ve
are s ll produced in today’s industry. In
terminal of the ba ery.
electrolysis, an electric current is sent through
an electrolyte and into solu on in order to
s mulate the flow of ions necessary to run on
Aim : To carry out electrolysis of water.
otherwise it is a non-spontaneous reac on.
Method:
Processes involving electrolysis include:
electro-refining, electro-synthesis and the Take a plas c vessel. Make two small holes at
chloro-alkali process. its bo om and set rubber stoppers in the
holes, insert carbon electrodes in these
When electricity is passed through certain
rubber stoppers and connect three electr-
solu ons, they decompose into charged atoms. odes to a 6 volt ba ery and a switch.
This process is called electrolysis. The solu on
Fill the vessel with water such that the metal
which conducts electricity and undergoes
caps of the carbon rods are outside the
decomposi on is called electrolyte. The two
water.
rods or plates dipped in solu on (liquid) and
Take two graduated test tubes filled with
connected to the posi ve terminal of ba ery is
water and invert them over the two carbon
called anode, while that connected to the
rods. Now, switch on the current.
nega ve terminal is called cathode.

154 Science-8