1

2

1.0 INTRODUCTION

Electrochemistry is a branch of chemistry dealing with chemical reactions that involve

electrical currents as well as electrical potentials. A chemical reaction that proceed

spontaneously and able to generate electrical current are known as electrochemical reaction.

As a vice versa, a chemical reaction that is forces to proceed by using electrical current are

called electrolysis. Electrochemistry is highly conceptual where many students believe that

this topic difficult and they must understand the abstract concept through three basic

components. These basic components are shown in figure 1.1 (Johnstone, 1999).

Figure 1.1 : The Chemistry triangle

The interactions and distinctions between the triangles are important characteristics of

chemistry learning and necessary for achievement in comprehending chemical concepts.

Therefore, if students possess difficulties at one of the levels, it may influence the other

(Sirhan, 2007). According to Johnstone (1999), the teaching and learning activities should

cover a dynamic blend of macro, submicro, and symbolic elements. Unfortunately, most

chemistry teaching is focused on the submicro–symbolic pair of the triplet and rarely helps

students to build bridges to comfortably move between the three levels. This teaching

approach often results in confusion and information overload, with negative consequences on

student motivation and achievement in the chemistry classroom (Talanquer, 2011). This

situation causes misconception among students. The common students’ misconceptions are

shown in figure 1.2 (Sanger & Greenbowe, 1997).

The macro and tangible: what can be

seen, touched and smelt

The submicro: atoms, molecules, ions and

structures

The representational: symbols, formulae, equations, molarity,

and graphs

3

Figure 1.2 : The common students’ misconception

Thus, determining and overcoming these difficulties should be the primary goal. The teaching

and learning activities should be the combination of these three basic components. Therefore,

the suitable method that can be applied is 3E learning cycle which consists of three stages

that are; engage, empower and enhance.

Electrons can flow through aqueous solutions without

assistance from the ions

Cations in the salt bridge and the

electrolyte accept electrons and

transfer them from the cathode to the

anode

Anion in the salt bridge and the

electrolyte transfer electron from

cathode to anode

Electron move through solution by being attracted from one ion to the other

Only negative chargeed ions

constitute a flow current in the

electrolyte and the salt bridge

4

Engage

Engage is an introductory activities to attract student attention and interest toward a new

concept. Through these activities, teachers are able to access the learner’s prior knowledge

and help them become engaged in the concept. The introductory activities can be a

demonstration by teacher, an issue or a problem, reading related articles or any task that can

promote curiosity and elicit prior knowledge. Then teachers will allow their student to think

and give respond from the stimulant given. From the responds given by the students, teacher

can identify if there is any misconceptions too.

Empower

During empower, the knowledge that has been eliciting will then be proven by doing some

experiment. From the experiment, students will be more understanding and well known with

the theory or principle included in the topic. Cooperation between groups members are very

importance. The restructure ideas also happen.

Enhance

To understand chemistry is to understand the world around us and what happened behind the

phenomena. There is simply no value to the argument that understanding chemistry can't help

us in daily life. So, enhance is one of the process in learning which is students try to relate the

theory of chemistry with the daily life situation. The knowledge that has been given to

students will be test with some of question regarding to the topic. In addition, through this

part it also can develop the problems solving skills and decision making among the students

because the more students know, the more they are able to make a smart decisions about life

choices.

What is 3E

Learning cycle?

5

2.0 TEACHING WITH 3E

A 3E model for galvanic cell was developed based on the learning outcomes stated in the

syllabus of Matriculation College in Malaysia.

Topic: Galvanic Cell

Learning outcomes:

At the end of the lesson, students should be able to answer:

Draw a Voltaic/ Galvanic Cell

Describe the operation of a voltaic cell

State the function of salt bridge

Write half-cell equations and the overall cell reaction equation.

6

2. 1 ENGAGE

Tutti Fruity Batteries (Demonstration)

Duration : 5-10 minutes

Demonstration of a simple galvanic cell by using fruit, metals strips and LED.

Purpose

To introduce galvanic cell and to show that some fruits can serve as

electrolytes.

Materials

Magnesium strips and copper strips

Red light emitting diode (red LED)

2 Connecting wires with clips on both ends

2 Lemons

Voltmeter

Procedure

1. Polish the metal strips with sand paper.

2. Roll and squeeze the lemon on a bench top to loosen the juices

inside - don't squeeze too hard.

3. Cut two slits on top of the lemon, 1 to 2 centimeters apart. Insert the

magnesium strip into one slit and zinc strip into the other.

4. Connect the strips to the voltmeter and LED with connecting wires.

5. Read the electric potential in volts and observe whether the LED is

lit up.

* Alternatively, it is encourage that teacher request students’ to

observe what will happen to the LED.

7

Diagram 1 : The complete diagram of the lemon galvanic cell

What’s happening?

A galvanic cell which converts chemical energy to electrical energy is created. In the process,

a redox (oxidation and reduction) process occurs. The magnesium metal will act as anode and

copper as cathode while the liquid lemon (citric acid) act as electrolytes. It is the same

process as the electricity produced in a battery.

Justification:

Electrochemical cell is all around us and it plays an important role to technological advances

that involves energy storage. The concept is introduced to student by using a galvanic cell

created from fruits that they eat in order to attract their attention and interest. This activity

will stimulate students’ curiosity and encourage them to ask their own. For example; why the

lemon can light up the LED? How does the lemon light up the LED? Hence, students will be

eager to learn about the concept being introduced.

8

2.2 EMPOWER

Activity 1 : Galvanic cell animation

Duration : 10 minutes

In this activity, you and your partner will be working with a computer animation that covers

electrochemical cell. Please log on on the following URL:

http://www.youtube.com/watch?v=C26pH8kC_Wk

While watching the animation, please discuss each question with your partner and write down

your best answer using the worksheet provided.

Discussion questions:

No. Questions Answer

1 The half-cell at anode consist of

_______________

A zinc bar placed into a zinc sulphate

solution

2 The half-cell at cathode consist of

_______________

A copper bar placed into a copper sulphate

solution

9

3 What is the salt bridge used in the

experiment?

NaCl salt bridge

4 What is the function of salt bridge?

To prevent the two electrolyte from mixing

and allow ions to migrate

5 Which direction does the electron

flow?

Electrons flow from Zinc electrode to

Copper electrode

6 Why Zn is likely to lose electron? Zinc is more active metal than carbon

7 Which metal undergoes oxidation? Zinc metal

8 What can you observe during the

oxidation process?

Zinc metal oxidized and form zinc ion and

release two electrons.

9 Which metal undergoes reduction? Copper metal

10 What can you observe during the

reduction process?

Copper ion in the solution gains two

electrons and reduced to copper metal and

deposited on the cathode.

11 How does the excessive SO42-

ions are

neutralized?

Sodium ions from salt bridge migrate into

copper sulphate solution and neutralized

the excessive SO42-

ions.

12 How does the excessive Zn2+

ions is

neutralised?

Chloride ions from salt bridge migrate into

zinc sulphate solution and neutralized the

excessive Zn2+

ions.

Justification:

The first activity for the empower stage started with the animation of galvanic cell, where this

animation only takes less time (2.08 minutes) but it is good enough for the students to learn

the abstract concept of galvanic cell. Besides that, the animation can makes them enjoy more

to learn difficult things and helps them to solve the problem of the imagination-skill in

galvanic cell. Therefore, the ability to practice new concepts in a risk-free environment

improves learners' skills and abilities. Furthermore, it also improves the skills and ability of

instructors because they will be able to change their way of teaching to be better. Hopefully,

from this activity, students able to understand the concept of galvanic cell in a dynamic blend

of macroscopic, submicroscopic, and symbolic elements.

10

Activity 2: Riding bicycle uphill and downhill

Duration : 30 minutes

In this activity, you will explore two kind of processes involve in redox reaction. Read the

story while referring to the given diagram.

Here goes is the story:

One fine day, Ana rides her bicycle to her friend Kai en's house and returns home by the

same route. Ana has to ride her bike going uphill and downhill. While going uphill, she

experience that it takes a lot of effort to climb uphill and the riding also become slower. She

also found that climbing hills on a bicycle isn't everyone's idea of fun. After finished climbing

uphill, she has to ride down hill which more fun, faster and she did not need to pedal at all.

What is the process involve in this two situations? Let’s us discuss what is happening.

Discussion question:

In your opinion, why Ana hate bike while going uphill?

What would happen if the Ana stops putting energy/stop paddling while going uphill?

Do you need to pedal while going downhill?

Going uphill Going downhill

Only happen when if energy is

continuously put into the process. If you

stop putting energy, you will fall off your

bike and roll down hill.Thus, going uphill

on your bike is non-spontaneous

Happen without having to put an energy

into it. Thus, going downhill is spontaneous

reaction

11

Click on the following URL and watch video to explore and get more information:

Have Fun!

http://www.youtube.com/watch?v=1HhXJ4RouUE

After you had finished watching the video, you can answer the following question based on

your understanding?

1. Name the two types of processes involve in redox reaction.

Spontaneous and non-spontaneous

2. What is spontaneous reaction?

A spontaneous process is the process that occurs under the given the set of conditions.

It process can occur without needing to be driven by an outside source of energy

3. We encounter spontaneous processes every day, but we never realize that they are

spontaneous. Can you give the everyday life example for the spontaneous reaction?

Here are few examples:

Water freezes spontaneously below 0 oC, and ice melts spontaneously above

0 oC at 1 atm pressure.

Heat flows spontaneously from hotter object to colder object, but not other

way around.

A water fall (Niagara Falls or dams) runs spontaneously downhill, but never

uphill

12

When you put a sugar in a cup of coffee, it dissolves spontaneously but it

does not reappear in its original form

Rusting of iron nail when it exposed to moisture and oxygen is spontaneous.

So is tarnishing of the silverwares.

4. What is non-spontaneous reaction?

A non-spontaneous process is the process that does not occur under the specified set of

condition (does not occur naturally). Non-spontaneous reactions require an input of

energy to take place.

5. Which process involve in galvanic cell? Why you said so?

A galvanic cell is a spontaneous electrochemical cell that produces electricity by a

spontaneous redox reaction. Because there is no source of energy used in the galvanic

cell.

6. How the process stated above occur in galvanic/voltaic cell?

A galvanic cell produces electrical energy as a result of a spontaneous redox process.

The electron transfer characteristic of such a process is made to occur in two separate

half-cells. Electrons released during an oxidation half-equation flow through a wire or

other external circuit before they can be accepted in a reduction half-equation.

Consequently an electrical current is made to flow. Thus, the chemical energy change

to electrical energy.

Justification:

In this activity, analogy method is used to facilitate students’ in understanding the concept of

spontaneous and non-spontaneous reaction in electrochemical cell. The analogy used is based

on their exposure to daily life activity that they had experienced thus resulting in meaningful

learning and deep understanding of the concept.

13

Activity 3 : Galvanic cell Pre-lab simulation

Duration : 15 minutes

In this activity, you and your partner will be working with a computer simulation that covers

electrochemical cell pre-lab as a preparation before begin your experiment. Please log on on

the following URL:

http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/electroChem/voltaicCel

l20.html

Please discuss each question with your partner and write down your best answer while

exploring the simulation.

1. Begin by assembling a zinc-copper cell. Please be sure to follow the instructions on the

screen.

2. Complete the following table of Silver Copper.

Questions Silver Copper

Is there an electron transfer

between species?

Yes Yes

14

Mark the species that loses

electrons

√ X

Write down the oxidation half

reaction under the species that is

undergoing oxidation.

Ag (s) → Ag+ (aq) + e

- X

Mark the species that gains

electrons

X √

Write down the reduction half

reaction under the species that is

undergoing reduction.

X Cu2+

(aq) + 2e - → Cu (s)

Mark the anode √

Mark the cathode √

3. Is this a spontaneous reaction? Explain your reason.

Yes because chemical energy in converted to electrical energy and no battery is

needed to operate the cell.

4. Write the complete balanced equation for the reaction.

Cu2+

(aq) + Ag (s) → Ag+ (aq) + Cu (s)

Justification:

The third activity is the galvanic cell pre-lab simulation. This simulation can serve to

introduce the ideas and equipment of the lab experiment allowing the students to work

through the laboratory faster and with less confusion. It can be given to a student group to

solve challenging problems that require multiple steps. This strategy allows students to

understand the material more clearly by engaging in a demanding, higher order thinking skills

problem. Besides that, the simulations can help students build mental models where they can

visualize concepts that appear on textbooks or hear from their teachers in lectures. By using

the simulation they can see a concrete situation that helps them build a mental model. The

simulations are great tools to help students recognize how equations relate observations and

the process occur at anode and cathode.

15

Activity 4: Galvanic cell experiment

Time duration: 2 hours

In this activity, you and your partner will construct Zinc - Copper cell, record the standard

cell potential, E cell and the observation at both anode and cathode.

Objective :

To construct the electrochemical cell for zinc and copper

To determine standard cell potential, E cell

To observation the reactions occur at both anode and cathode.

The apparatus and chemical reagents needed are as follows :

Apparatus :

Beaker (50 mL) KCl salt bridge Wire & voltmeter Sand paper

Chemical reagents

Copper strip Zinc strip Iron strip Magnesium strip

1.0 M CuSO4

1.O M ZnSO4

1.O M FeSO4

1.0 M MgSO4

16

Please be sure to follow the instructions listed in the diagram below:

1

• Clean the metal strips with abrasive cloth.

2

• Fill a 50 mL beaker with 35 mL of 1.0 M CuSO4 and other beaker with 1.0 M ZnSO4

3

• Set up the apparatus by using the apparatus and chemical reagent provided.

4

• Record the standard cell potential E ̊cell and the observation at both anode and cathode.

5

• Repeat step 1 - 4 by replacing Zn2+ /Zn half cell with:

• Magnesium strip in 1.0 M MgSO4

• Aluminium strip in 1.0 M Al(SO4)3

• Iron strip in 1.0 M FeSO4

17

Please discuss each question with your partner and write down your best answer using the

worksheet provided.

Question Cell 1 Cell 2 Cell 3 Cell 4

Zn – Cu cell Mg – Cu cell Al – Cu cell Fe – Cu cell

Which metal

undergoes

oxidation?

Zn Mg Al Fe

What can you

observe the

condition of the

metal strip after

undergoes

oxidation? Give

your reason.

Zn electrode

become thinner.

Zinc metal

oxidized and

form zinc ion

and release two

electrons.

Mg electrode

become thinner.

Mg metal

oxidized and

form Mg ion

and release two

electrons.

Al electrode

become thinner.

Al metal

oxidized and

form Al ion and

release two

electrons.

Fe electrode

become thinner.

Fe metal

oxidized and

form Fe ion and

release two

electrons.

What can you

observe the

condition of the

metal strip after

undergoes

reduction

process? Give

your reason.

Cu electrode becomes thicker.

Copper ion in the solution gains two electrons and reduced to copper

metal and deposited on the Cu electrode.

Justification:

This activity will promote the science education goals regardless of the topics learned. It

encompasses a wide area of ―hands on‖ laboratory skills with the equipment and chemicals

employed and at the same time putting in practice the theoretical knowledge gained in the

class-room. Besides that, this activity also can sharpen the manipulative skills as well as

science process skills. This activity also promotes critical skills such as report writing, data

handling, and the ability to interpret and evaluate evidence.

18

Activity 5: Let’s Play Electrochem Puzzle!

Duration: 1 hour

In this activity, you will play a game to build understanding of the chemistry involved in

galvanic cell. First, you have to illustrate how all the pieces of an electrochemical cell come

together to produce a charge. You will play this puzzle in a group of 2.

Note: In order to play the game your students must have a working understanding of

oxidation-reduction reactions, setting up the circuits, able to balance the equations and set up

chemical equations.

Teacher Preparation:

1. Print, cut out and organize the game puzzle pieces.

2. Let student form a group (Think-pair share).

3. Distribute game pieces to student pairs.

How to play the puzzle game?

1. All groups is provided with a mounting board, puzzle pieces (electrode, electrolyte,

salt bridge & voltmeter), thread, map pin and standard electrode potential table,

labeling card (write function and to label the puzzle).

2. Decide whether the metal will be an oxidizing agent and reducing agent. Match the

metal with the proper electrolyte. Then, place it in the beaker.

3. Set up the galvanic cell using the apparatus.

4. Label the cell diagram using labeling card and use map pin to attach it on board.

5. Present your complete puzzle to your friends. Explain the function of each tool that

needs to complete the circuit.

6. Make a half cell equation at anode and cathode using the puzzle pieces provided.

Next, form a balanced net reaction for the cell and calculate the Eocell of your reaction.

Key concepts

Oxidation: an atom or ion loses electrons

Reduction: an atom or ion gains electrons

In an oxidation reaction, the atom or ion becomes more

positive due to the loss of electrons.

In a reduction reaction, the atom or ion becomes more negative

due to the gain of electrons.

19

Discussion question:

1. Do we need a battery/source of energy to complete the circuit? Why?

No, because this is spontaneous reaction. It can occur without the source of energy.

2. Why you need galvanometer/voltmeter in galvanic cell?

To measure voltage.

3. Why do you think the game included a salt bridge? Why might this be important?

Salt bridge will complete the circuit and neutralize the successive ion at cathode

and anode.

4. What would happen if there is no salt bridge?

Without the salt bridge, the spontaneous reaction would not occur. There would be

no flow of electrongs, or charge, and no reaction would take place.

Reflection:

Do you think the activity is fun?

What are the problems encountered during you run the game?

How would you play differently next time to make it more interesting?

Note:

At the end of this activity, student will give feedback about their perception of the puzzle

games. Teacher can use the suggestion question above or depends on teacher creativity. The

reflection will help teacher to know the weaknesses and the strength of this activity and at the

same time it can help teacher to improve this lesson.

Justification:

The electrochem puzzle is an activity that can be used to reinforce student’s knowledge and

at the same time it can provide your student to learn in fun environment. Student will

participate actively during the activity because they need to discuss the correct component of

puzzle pieces to be use and arrange it form a puzzle. At the same time, this activity will train

student in problem solving. Teacher will ask questions to probe students’ thinking on why

they choose the components of puzzle pieces.

20

Here is the part of puzzle pieces all come together to form the galvanic cell .

21

2. 3 ENHANCE

Task 1 : Dental Filling Discomfort

Adam has an appointment with the dentist today. The dentist finds a cavity on his second

molar and needs to have it filled. After the visit to the dentist, Adam stops by to buy his

favorites Cadbury chocolate. Once he reaches home, Adam starts to eat the chocolate. While

enjoying the chocolate, Adam accidently bites a piece of the aluminum wrapper without

realizing it. He immediately feels a sharp pain on his second molar.

Why do you think

Adam experience

such pain?

22

Answer:

Anyone who bites a piece of aluminium foil (such as that for wrapping candies) in such a way

that the foil presses against a dental filling will probably experience a momentary sharp

pain. In effect, an electrochemical cell has been created in the mouth, with aluminium (E° = -

1.66 V) as the anode, the filling as the cathode, and saliva as the electrolyte. Contact between

the aluminium foil and the filling short-circuits the cell, causing a weak current flow between

the electrodes. This current stimulates the sensitive nerve of the tooth, causing an unpleasant

sensation.

Justification :

This task enables students to relate the theory of galvanic cell that have been learned before

with the real life situation. Besides that, students will realize about the importance of

chemistry because having a solid knowledge of chemistry will vastly improve our quality of

life. Without an understanding of chemical properties and principles, life as it is today would

not be possible. Hence, students are able to explore beyond the concept about the phenomena

of electrochemical cell in real life situation.

23

Task 2 : Oh, Corrosion!

In your opinion,

Why metal in houses along the beach corrode faster than inland houses?

VS

Oh, Corrosion!

Corrosion of metals means the spontaneous deterioration that most metals undergo due to

chemical reactions with their environment, these reactions generally producing salts or

oxides of the metals. Corrosion leads to grave loss of strength in metallic structures and

machinery, and therefore is of immense economic and human importance.

In metals, corrosion generally occurs in an electrochemical way, via development of

many tiny galvanic cells on the metal surface. Some parts of the metal surface act as

anodic sites, where the metal gets converted to its cations in an oxidation process

whereas some other parts of the metal surface, on the other hand, acts as cathodic sites

(the tiny cathodes) where cathodic reactions takes place. The ions involved in the

electrode reactions travel via the moist or aqueous surroundings of the metal, thereby

completing the electrical circuit.

24

Water pipe gets corroded particularly at the joints. Why is it so?

Answer:

Why metal in houses along the beach corrode faster than inland houses?

During the rusting process, moist or water surrounding the metal acts as the medium to

transfer the ions (salt bridge). The presence of salt speed up corrosion rate water because

salt water greatly facilitates ionic conduction.

Water pipe gets corroded particularly at the joints. Why is it so?

In metal, the anodic sites are those areas that have low oxygen concentration. For examples,

crevices, contact areas between part and parts covered with dirt. Cathodic sites on the other

hand, are those with high oxygen availability where oxygen would get reduced.

Anodic sites are where metal is oxidized to ions which mean it is the part that is getting

corroded. Hence, for any metal equipment it is easier to corrode at area which has low

oxygen concentration.

25

Note:

Cathodes reactions do not cause any harm to the body of the metal (while the anodic

reactions are eating up the metal).

Justification:

Students are able to explore the concept beyond the classroom wall and into the phenomena

of electrochemical cell experiences in real life situation. Students will read a short article on

corrosion first before questions is given. The questions given have enough structure to give

students direction but open-ended enough to engage their imaginations, this activity teaches

students the application of the concepts in daily life in an enjoyable way.

3.0 CONCLUSION

Science teachers continuously strive to improve their instructional practices to develop an

effective instructional model can help students learn fundamental concepts in science.

Therefore, the use of coordinated and coherent sequencing of lesson-learning cycles and

instructional models intergrated with techology has gained popularity in the science

education community. One of the example is the 3E insturctional model. Complementing the

aims of science teachers, the 3E instructional model facilitate connections between teachers

the curriculum and students. Therefore, we are hopeful that the 3E module develop by using

appropriate internet, comunication and technology tools will benefits teachers and encourage

more teachers to implement this method in science classroom. Besides, this module will

serve as guidance for teacher who is interested to carry out this method to enhance students’

learning experience.

26

4.0 REFERENCES

Corrosion of Metal. Retrieved April 4, 2013 from

http://www.learner.org/courses/envsci/visual/visual.php?shortname=oxidation

Lemon battery challenge. Retrieved from April 8, 2013 from

http://www.csiro.au/helix/sciencemail/activities/lemonbattery.html

Spontaneous vs. non-spontaneous reaction. Retrieved April, 6, 2013 from

http://www.youtube.com/watch?v=IHhXJ4RouUE

Sirhan, G. (2007). Learning Difficulties in Chemistry: An Overview. Journal of Turkish

Science Education. 4 ( 2) , 2-20

Johnstone, A. H. (1999). Teaching of chemistry: Logical or phycological. Chemistry

education: research and practice in europe. 1 (1), 9-15

Talanquer, V. (2011). Macro, Submicro, and Symbolic: The many faces of the chemistry

―triplet”. International Journal of Science Education, 33 (2) 179 — 195, Retrieved

October, 12, 2012 from DOI: 10.1080/09500690903386435

The galvanic cell game. Retrieved April 5,2013 form

http://www.cornell.edu/rct/modul/documents/GalvanicCellGame.pdf

Raymond C. (2005). Chemistry. Chemistry in action. McGraw-Hill, New York (8th

Ed.)

Matriculation Division Ministry of Education. (2011). Chemistry Laboratory Manual

Semester 1,2,3 and 4 Two Year Programme. Perak : Tijary Niaga.