25 June 2013
J Brewin Deer Park School
Learning Objectives
• By the end of the lesson I will be able
to:
• 1) Understand the process of
electrolysis.
• 2) Explain how we can use electrolysis
to extract aluminium from its ore.
J Brewin Deer Park
School
Match up the words with their
descriptions
Test for Oxygen
Test for Hydrogen
Electrolyte
The substance being broken down
Positive electrode
Makes a ‘popping’ noise when lit
Anode
Relights a glowing splint
Cathode
Splitting a substance using
electricity
Electrolysis
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School
Negative electrode
Electrolysis is splitting up
substances using
electricity
(Lysis is latin for splitting)
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School
What is electrolysis?
• Electric current is used to
breakdown a substance made
up of ions
• An electrolyte is the name for
the substance being broken
down
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School
Don’t get stressed
in the exam:
Remember PANIC
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School
•Positive
•Anode
•Negative
•Is
•Cathode
Aluminuim oxide electrolysis
• Molten aluminium oxide is created by dissolving the
aluminium in molten cryolite.
• This forms the electrolyte, through which electricity
can pass.
• An electric current is passed through the electrolyte.
• This causes the aluminium oxide to split into
aluminium and oxygen.
• Aluminium ions are positively charged (cations) and go
to the..
• Cathode
• Oxygen ions are negative (anions) and go to the...
• Anode
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School
Electrolysis of Molten NaCl
+
ANODE
+
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School
CATHODE
The metal goes to
the cathode and the
non metal goes to
the anode.
Na+
ClNa+
-
Na+
Cl-
ClNa+
-
Cl-
+
-
negative electrode
positive electrode
(anode)
(cathode)
Zn+
Zn+
Cl-
molten zinc
chloride (ions free
to move)
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School
ClZn+
Cl-
ClZn+
ClZn+
Zn+
Zn+
Cl-
Cl-
ClZn+
The
positively
charged zinc
ions are
attracted to
the negative
electrode
+
-
Zn+
Zn+
ClCl-
Cl-
Zn+
ClZn+
Cl-
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School
Zn+
+
The negatively
charged
chloride ions
are attracted to
the positive
electrode
-
+ +
ZnZn
Zn+Zn+
Cl-
Zn+
ClClCl-
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School
Cl-
True or False
• Electrolysis is the splitting of a
substance using electricity.
• The anode is negative.
• Anions are negative
• Aluminium oxide is found in bauxite.
• Cathode is negative.
• Cations are negative.
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Compound
Sodium
Bromide
Potassium
Iodide
Calcium
Fluoride
Magnesium
Oxide
Lithium
Chloride
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Anode
Cathode
= bromide ion
= lead ion
Cathode
Anode
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O.I.L.R.I.G.
•Oxidation is loss
of electrons
•Reduction is gain
of electrons
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School
= bromide ion
At the cathode:
Pb+ gains electrons to form
lead metal.
= lead ion
It is REDUCED.
Cathode
Anode
At the anode:
Br- loses electrons to form
bromine gas.
It is OXIDISED.
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Cathode
Negative
Anode
Positive
Positive ions
attracted
Negative ions
attracted
REDUCTION
happens here (
positive ions gain
electrons)
OXIDATION
happens here
(negative ions
lose electrons
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School
Stand up sit down
1. One person names a topic.
2. All pupils write a key word to do with the
topic on a whiteboard
3. The person who chose the topic has 30
seconds to name as many key words to do
with the topic as they can.
4. If the word the pupil has written down is
said they have to sit down.
5. The aim for the topic chooser is to get
everyone to sit down.
6. The aim for the pupils writing down a word
is to out fox the topic chooser with a
relevant but obscure word.
J Brewin Deer Park
School