lesson plan 2
TRANSCRIPT
Learning Area : Electrochemistry
Topic : Electrolysis in Aqueous Solutions
Date : 10th March 2011
Class : 4 Einstein
Time : 40 minutes
No. of students : 10
Learning Objective : Analysing the electrolysis of aqueous solutions
Learning Outcomes : Students should be able to :
a) Identify the cations and anions in an aqueous solutions.
b) Describe the electrolysis of an aqueous solutions.
c) Write half equations for the discharge of ions at anode and cathode.
Science Process Skills :
Scientific Attitudes and Noble values:
Thinking Skills :
Prior Knowledge : a) Students had already learned about the periodic table in Chapter 4.
(Metal and non-metal elements)
b) Students already learned about electrolytes and non-electrolytes.
c) Students had discovered the electrolysis in molten compound.
Teacher’s References : i) Websites:
http://www.gcsescience.com/ex.htm
http://www.myadvocators.com/chemistry/quick-revision-series/electrolysis/electrolysis-
of-aqueous-solutions/
ii) Books:
Chemistry Form 4, Integrated Curriculum For Secondary Schools
Low swee Neo, Lim Yean ching, Eng Nguan Hong, Lim Eng Wah and umi Kalthom binti
Ahmad, 2005.
Laboratory Manual :Green Chemistry An Approach That Addresses Education for
Sustainable Development.
Mageswary Karpudewan, Zurida Hj Ismail and Norita Mohamed, 2009/2010.
Student’s References : Books
Chemistry Form 4, Integrated Curriculum For Secondary Schools
Low swee Neo, Lim Yean ching, Eng Nguan Hong, Lim Eng Wah and umi Kalthom binti
Ahmad, 2005.
Lesson Plan:
Step Content Teacher’s Activity Student’s Activity Remarks
Step 1
(± min)
Induction set Teacher asks students :
a) definition of electrolysis.
b) definition of electrolytes.
With the help of diagram, teacher
asks students to recall the 3 main
components in electrolysis process.
Students recall back what they
learned in previous lesson :
Expected answer :
a) A process whereby an
electrolyte is broken down
into its constituent elements
with the help of electric
current.
b) Electrolytes are substances
that can conduct electricity.
Students review back the 3 main
components based on electrolysis in
molten compound that they learned
in previous topic.
Expected answer :
1) Electrolytes
2) Direct current (battery)
3) Electrodes
Teaching aids:
Whiteboard
Manila card
Power point
Periodic Table
Aims :
a) Actively
engage
students with
teaching and
learning
process.
b) To induce
students to
make use the
previous
lesson and
make
Using the diagram before, teacher
discuses generally the electrolysis
in molten compound using NaCl as
electrolytes. (What happen to this
NaCl electrolyte if I heat it up?)
Teacher pause the lesson and asks
students weather they still
remember how to determine which
the elements that will form cations
and which elements will form
anions?
e.g NaCl
Na+ = Metal element
Cl- = Non-metal element
Teacher asks students the number
of ions present in the molten
electrolytes after the electric current
is passed through it.
Students express their opinion about
molten compound.
(Expected answer : NaCl electrolytes
will melting)
Students recall back what they
learned in the Chapter 4 of Periodic
Table.
Expected answer :
All metals form cations while non-
metal will form anions.
Expected answer :
Two types which are Na+ and Cl-.
connection
between the
previous
topic with the
new lesson.
c) To help
students get a
better idea by
using the
manila card.
Teacher asks students to identify
what happen to the electrolyte if
instead of melt it up the water is
add up into the beaker.
Teacher asks students how many
types of ions will present in the
aqueous solution electrolytes.
Teacher guide the students to
identify the topic to be covered in
the teaching and learning process.
Students respond to teacher by state
that the electrolytes will dissolve in
the water and become an aqueous
solution.
Expected answer :
Four types of ions which are Na+,
Cl-, H+, and OH-.
Students can identify that they are
going to learn about electrolysis in
aqueous solution.
Step 2
(± min)
Identify cations and
anions in aqueous
solutions.
Teacher show a video on
electrolysis process of NaCl
solutions. Teacher asks students to
take note the type of ions present i
n the animation and the movements
of the ions to their respective
electrodes.
Based on the video, teacher give
Students observed the video
critically.
Students give appropriate responses
Teaching aids:
1. Power point
2. Whiteboard
3. Manila cards
4. Diagram
5. Worksheets
series of questions:
a) What are the ions present in
the video?
b) What is the similarity
between H+ and Na+ ions?
c) What is the similarity
between OH- and Cl- ions.
d) Where do the positive
charge ions go?
e) Where do the positive
charge ions go?
Teacher explains the difference
between anode, anions cathode,
and cations using an analogy of a
boy and a girl. (the electrodes is
named differently because they are
attached to different terminal of DC
(battery))
With the aids of diagrams teacher
tells students that the boy and girl
to teacher.
Expected answer :
a) Na+ H+ Cl- OH-
b) Both are positive ions
(cations)
c) Both are negative ions
(anions)
d) Positive ion goes to cathode.
e) Negative ion goes to anode.
Student analyses teacher’s
explanations about the analogy that
represents the movements of anions
to anode and cations to cathode.
Aims:
1. The use of
analogy is to
reinforce
students
understandin
g that a
different sign
of electrodes
will attract
different sign
of ions.
will represent the electrodes :
Girl = Anode
Boy = Cathode
Teacher asks students :
a) In your opinion, a girl will
attract to a boy or a girl?
b) So, these two little boys will
represent which ion? Cation
or anion?
c) Based on your opinion, how
about the boy? Who will
they attract to?
d) So, these two little boys will
represent which ion? Cation
or anion?
*Boy = Cathode and cations
Girl = Anode and anions
Teacher guides students to make a
conclusion that the different sign of
cathode (-ve sign) will attract a
Expected answer :
a) Boy
b) Anions
c) Girl
d) Cations
Students review the analogy to be
applied into the real cases of
movements of ions towards their
opposite sign of ions (cations +ve
sign).
Teacher gives an activity to the
students to familiarize them with
the different types of electrolytes.
Activity 1 : (Drill and Practice
Puzzles)
a) CuSO4 solution
b) ZnCl2 solution
c) PbBr2 solution
d) MgSO4 solution
Teacher gives a tip on how to
remember that cations are positive
charge and anions are negative
charge.
The tip is :
Cations
respective electrodes.
Students practice their understanding
in determine the cations and anions
and their movement towards anode
or cathode. Drill practice puzzle.
Expected answer :
Cathode
(cations)
Anode
(anions)
a) Cu2+ H+ SO42- OH-
b) Zn2+ H+ Cl- OH-
c) Pb2+ H+ Br- OH-
d) Mg2+ H+ SO42- OH-
Students will employ the tip to
prevent them from interchange the
positive and negative sign of the
charges.
The letter ‘t’ in the middle of
cations will represent the positive
sign of the ions.
Anions
Anions is stands for A Negative
Ions
Step 3
(± min)
Effect of positions of
ions in
electrochemical series
Teacher asks students to recall back
the analogy of a boy and a girl in
explaining the movements of
electrons in aqueous solutions.
Teacher encourage the student to
think critically and creatively by
saying :
a) In this case there are two
girls at the cathode right,
but which one will be
choose by cathode?
b) The same goes at the anode
because there exist two boys
and how can we know
which one will be choose by
Students recall back the analogy.
Students respond to teacher
accordingly.
Expected answer :
a) The one that are more pretty
or kind etc.
b) The one that are more
handsome and macho etc.
anode?
Teacher asks students to apply the
concept in the analogy into
electrolysis process. (instead of
how pretty or handsome the ions
are, in electrolysis we will
determine which ions will be
choose to further react by looking
at its ease of discharges abilities)
Teacher shows Electrochemical
Series Diagram and help students to
make a mnemonic in order to make
it easy to remember.
Cation (up) Mnemonic
K+ Kalau
Na+ Nak
Ca2+ Cantik
Mg2+ Macam
Students will apply the balloon
analogy into half equations of
electrolysis in aqueous solutions.
Al3+ Angelina
Zn2+ Zuli
Fe2+ Faustina
Sn2+ Suruh
Pb2+ Pergi
H+ Hutan
Cu2+ Cari
Ag2+ (down) Antu
*the ease of discharge increases
down the series
Anion (up) Mnemonic
F- Fazira
SO42- Suka
NO3- Nak
Cl- Cucuk
Br- Belakang
I - Itik
OH- (down) OMG
*the ease of discharge increases
down the series
Teacher provides another activity
(Activity 2 : Choose The Best) for
the students using the same
electrolytes in Activity 1 (Drill and
Practice).
Teacher asks students to choose the
anions and cations that will react at
anode and cathode based on
electrochemical series using.
a) CuSO4 solution
b) ZnCl2 solution
c) PbBr2 solution
d) MgSO4 solution
Teacher reminds students that they
needs to remember the
electrochemical series and suggest
them to use mnemonic like the
teacher prepared.
Students participate in the activity
critically by firstly discuss it in the
group and later paste the answer on
the whiteboard.
Expected answer :
a) Cathode : Cu2+
Anode : OH-
b) Cathode : H+
Anode : OH-
c) Cathode : H+
Anode : OH-
d) Cathode : H+
Anode : OH-
Step 4
(± min)
Write half equations
for the discharge of
Teacher will introduce the ‘DTD
2E’s Steps’ to the students in order
Students will participate in the
discussion appropriately according to
Teaching aids :
1. Power point
ions at the anode and
cathode.
to illustrate the electrolysis
process :
1- Diagram (draw and label
the electrolysis diagram)
2- Table. (draw a table and
divide the table into two
columns for anode and
cathode)
3- Determine the cations and
anions.
4- Electrochemical Series
(Choose the ions that will
be choose to further react at
anode and cathode)
5- Equations (write equations
and balanced it)
For the last E in DTD 2E’s Steps
teacher will asks :
a) Which ions will donate
electron/s?
b) Which ions will accept
teacher’s instructions.
Students interpret which ions will
donate or accept electrons based on
their understanding about the process
occur at cathode and anode.
Expected answer :
Aims:
1- To test students
understands.
2- To make sure
students actively
involved in the
teaching and
learning process.
3- To activate
students
memorize the
steps in
illustrating
process in
electrolysis
using acronym.
electron/s?
Teacher gives a simple analogy
about the placement of electrons in
the right hand side (RHS) or left
hand side (LHS) of equations.
Let’s assume the electrons are a
balloon.
LHS of half equations is ourselves
and RHS is our friend.
Donate electrons
When we give a balloon to our
friend, of course the balloon will
not be with her or his and not with
us anymore. So, that’s why for
anions that donate electrons the half
equation will place the electron on
the RHS with the products and not
with OH- itself. (no longer be
together with anions that donate
electrons)
a) Anions
b) Cations
e.g :
4OH- (aq) 2H2O(l) + O2(g) + 4e-
Accept Electrons
But if our friends gift us a balloon,
of course the balloon that we accept
will be with us. So, the same goes
for cations when it accepts
electrons the electrons will be
placed LHS of the half equations.
(be together with cations that
accept electrons)
e.g :
Cu2+ (aq) + 4e- Cu(s)
Teacher asks students to think the
movement of electrons in
electrolysis process based on the
donation and accepting electrons
concept.
Step 5
(± min)
Conclusion Teacher re-shows the diagram of
electrolysis in aqueous solution and
guides students to re-explain the
Students give appropriate response to
teacher
process of electrolysis using DTD
2E’s steps using CuSO4 solution
and NaCl solution.
Teacher ask student to recall back
what they have learnt.
a. What is electrolysis of an
aqueous solution?
b. Give me steps in determine
the product in electrolysis
Teacher asks :
a) In your opinion can you
suggest the other factors
that will affect the
electrolysis?
b) What are the applications of
electrolysis in our daily
life?
a. In electrolysis of an aqueous
solution,hydrogen ions,H and
hydroxide ions,OH are also
present in addition to the
anions and cations of the
dissolves compounds.
b. DTD 2E’s steps
Expected answer :
a) Concentrations and types of
electrodes.
b) Rusty, coated brooch and etc.