What is Electrolysis? Video Lecture | Science Class 8

electrolysis is electrical current flow
through a liquid which causes chemical
changes yes you did hear that correctly
current flowing through a liquid now not
all liquids can conduct the liquid can
be a molten ionic compound or an aqueous
solution in either case it must be able
to carry current let's take a common
example table salt if you heat sodium
chloride to over 801 degrees Celsius it
will melt the liquid will contain
free-flowing positive sodium ions and
negative chloride ions this simply means
that sodium and chloride ions are free
to move within the liquid sodium
chloride positive ions are called
cations negative ions are called anions
now consider putting two electrical
conductors into the liquid copper would
be good as it has a higher melting point
nothing happens to the ions at this
point but if we connect the two bits of
copper to an electrical cell or power
supply then things start to get
interesting we do need to sidestep for a
moment to look at electrical current in
a metal from our lesson behavior of
metallic structures we know that
electrons in a metal aren't bound to
particular atoms they form a sea of
electrons that can move easily if a
potential difference or a voltage is
applied across it this could be from an
electrical cell or a battery the
electrons will begin to drift towards
the positive terminal of the battery and
this is what happens when current flows
current is the movement of charge in
this case electrons now let's go back to
our molten sodium chloride we've added
our copper wires
let's call them electrodes and now we'll
connect these to an electrical cell the
electrons will start to
floo in the wires and this will cause
one electrode to become positively
charged and the other negatively charged
this has an immediate knock-on effect in
the molten state employed which you'll
remember is a mixture of sodium cations
and chloride anions anything positively
charged in the liquid in this case the
sodium ions is going to be attracted to
the negative electrode and anything
negatively charged in this case the
chloride ions is going to be attracted
to the positive electrode this is
because opposite electrical charges
attract when the ions meet the
electrodes electron exchange happens and
this triggers a chemical reaction solids
can form gases can be given off and new
solutions can be left behind it all
depends on the liquid and what material
the electrodes are made from there is
more detail about this process in our
lesson interpreting electrode equations
there are special names for the
electrodes which are usually metal
plates with a larger surface area than a
piece of wire the positive electrode is
called the anode it attracts anions and
the negative electrode is called the
cathode it attracts cations the liquid
is effectively conducting electrical
current the only difference is that the
charge carries in the liquid in other
words the charged particles that are
moving are ions if a liquid has free
moving ions and can conduct like this it
is called an electrolyte remember that
electrolysis can also take place in
ionic solutions as well as molten
compounds the more concentrated that
solution the greater the ion flow rate
iron flow rate can also be increased by
increasing the potential difference or
voltage across the cell will be studying
several examples of electrolysis in more
detail in other lessons for the time
being though here is a summary of the
key ideas about electrolysis
electrolysis is the flow of electrical
current in a conducting solution or
molten liquid that causes chemical
changes the conducting liquid is called
an electrolyte and has free-moving
ions the conducting plates bars or wires
inserted into an electrolyte are called
electrodes positive ions are called
cations and are attracted to the cathode
negative ions are called anions and are
attracted to the anode when current
flows in an electrolyte it is the ions
that move and carry the electrical
charge when current flows in the
electrodes and wires it is the electrons
that move and carry the electrical
charge