SubjekSKP6024-Technology And Innovation In Teaching And

Learning Chemistry

Pensyarah Cik Hajjah Asmayati bt Yahaya

Jabatan Jabatan Kimia

Fakulti Fakulti Sains & Matematik (FMST)

Ahli Kumpulan

(Kumpulan 2)

1. Zainudin B Abdul Razak M20121000096

2. Mohd Akhmal B R.Azmi M20121000022

3. Mohd Taufik B Abd Hamid M20121000021

4. Mohamad Fariz B Ahmad M20121000013

Tarikh Penghantaran 13hb April 2013

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Simulation/Modeling Voltaic Cell

CONTENT PAGE

1.0 Introduction 1

2.0 Scientific Concept 3

3.0 Constructing a Cell Diagram 5

4.0 3E’s Element (Engaging, Empowering & Enhancing) 6

4.1 Engaging Phase 6

4.2 Empowering Phase 8

4.3 Enhancing Phase 10

5.0 Reflection 17

6.0 Reference 17

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CHAPTER 6 : ELECTROCHEMISTRY

VOLTAIC CELL

1.0 Introduction

There are many aspects of modern life that depend on electrochemistry, such as batteries. Many things run on batteries (laptop, phone, car, etc.), which are spontaneous electrochemical reactions. The electrochemical cells, known as a voltaic or galvanic cells, are cells that convert chemical

energy into electrical energy spontaneously. Every voltaic cell is made up of two half‐cells. Oxidation and reduction reactions make up the electrochemical reaction. Oxidation occurs at the anode (negative terminal) when electrons are lost by a substance. Reduction occurs at the cathode (positive terminal) when electrons are gained by a substance. It is customary to affiliate the anode

with a negative (‐) electrode, and the cathode with a positive (+) electrode when dealing with

voltaic cells. In a redox (reduction‐oxidation) reaction, the electrons are transferred from the reducing agent, which is oxidized, to the oxidizing agent, which is reduced. In other words, the electrons flow from the anode to the cathode.

Figure 1.1 Voltaic cell with Copper and Silver metals.

Redox reactions are commonly split into two half‐reactions. For example, the redox reaction

between copper and silver ions:

Cu(s) + 2Ag+(aq) → Cu2+

(aq) + 2Ag(s)

Copper is the reducing agent and is being oxidized, while silver is the oxidizing agent and isbeing reduced. The half‐reactions would then be:

Cu(s) → Cu2+(aq) + 2e‐ Oxidation at the Anode

2Ag+(aq) + 2e‐ → 2Ag(s) Reduction at the Cathode

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The copper, undergoing oxidation, is the anode and the silver is the cathode where silver (I) cations (Ag+) are being reduced. The voltmeter measures the voltage, or potential difference between the half‐cells. This voltage is represented by a capitol E.

2. 0 Scientific Concept

2.1 A voltaic cell is a device which converts chemical energy to electrical energy. The chemical reactions that take place inside the cell cause the flow of electrons and hence, electricity is produced.

2.2 Simple voltaic cell is made by placing two different metals in contact with an electrolyte as shown in figure 1. The metals act as the electrodes for the simple cell. The electrodes are connected to a voltmeter, a galvanometer or an electric bulb using connecting wires.

Figure 2.1: An example of simple voltaic cell

Source: Voltaic cell, retrieved from: http://berryberryeasy.com

2.3 The production of electricity in the cell will cause the bulb to light up, and make the voltmeter or galvanometer to show a reading.

2.4 The voltage of the voltaic cell is the sum of the voltages of the two half-cells. It is measured by connecting a voltmeter to the two electrodes. The voltmeter has very high resistance, so the current flow is effectively negligible. When a device such as an electric motor is attached to the electrodes, a current flows and redox reactions occur in both half-cells. This will continue until the concentration of the cations that are being reduced goes to zero.

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Electrode (Cu)

Voltmeter

Electrolyte

Electrode

Wires

Figure 2.2: Voltaic Cell (Copper-Silver)

An electrode is strip of metal on which the reaction takes place. In a voltaic cell, the oxidation and reduction of metals occurs at the electrodes. There are two electrodes in a voltaic cell, one in each half-cell. The cathode is where reduction takes place and oxidation takes place at the anode.

Figure 2.3 : Mechanism for Copper and Silver in anode and cathode

Through electrochemistry, these reactions are reacting upon metal surfaces, or electrodes. An oxidation-reduction equilibrium is established between the metal and the substances in solution. When electrodes are immersed in a solution containing ions of the same metal, it is called a half-cell. Electrolytes are ions in solution, usually fluid, that conducts electricity through ionic conduction. Two possible interactions can occur between the metal atoms on the electrode and the ion solutions.

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Metal ion Mn+ from the solution may collide with the electrode, gaining "n" electrons from it, and convert to metal atoms. This means that the ions are reduced. Metal atom on the surface may lose "n" electrons to the electrode and enter the solution as the ion Mn+ meaning that the metal atoms are oxidized. When an electrode is oxidized in a solution, it is called an anode and when an electrode is reduced in solution. it is called a cathode.

3.0 Constructing a Cell Diagram

Consider the following reaction:

2Ag+(aq) + Cu(s) → Cu2+

(aq) + 2Ag(s)

Step 1: Write the two half-reactions.

Ag+(aq) + e- → Ag(s)

Cu(s) → Cu2+(aq) + 2e-

Step 2: Determine the cathode and anode.

Anode: Cu(s) → Cu2+(aq) + 2e-

Cathode: Ag+(aq) + e- → Ag(s)

Copper (Cu) is losing electrons thus being oxidized. Oxidation happens at the anode. Silver ion (Ag+) is gaining electrons thus is being reduced. Reduction happens at the cathode.

Step 3: Construct the Diagram.

Cu(s) | Cu2+(aq) || Ag+

(aq) | Ag(s)

The anode always goes on the left and cathode on the right. Separate changes in phase by | and indicate the the salt bridge with ||.

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4.0 3E’s Element (Engaging, Empowering & Enhancing)

4.1 Engaging Phase

Activity:

Source: The Lemon Battery, retrieved from http://www.youtube.com/watch?v=DXir_ORHOGA&feature=related

Questions:

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Teacher shows a video from the internet to attract students’ attention to the topic which will be discussed. They are required to watch the video carefully.

After showing the video, students will be asked some questions in order to elicit their prior knowledge.

1. What your observations can be making from the video? 2. What is the function of lemon in the video?3. What cause the voltmeter shown a reading?4. Predict what will happen to the reading of the voltmeter and the brightness of led diode

when we add more lemon?5. What is the conclusion from the video?6. Can you relate the video with the topic will be discussed?

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Sample Answers:

1. (i) When the iron nail and the coin is connected using connecting wire, the voltmeter shows a reading.(ii) The led diode lighted up when the two metals were connected.

2. Electrolyte 3. The moving of electrons4. The reading of the voltmeter will increase and the led diode will

light up brighter.5. The moving of electrons will cause the flow of electric current.6. Voltaic cell/ galvanic cell

Teacher need to have an internet connection.

Teacher able to show the moving of electrons in voltaic cell by using the simulation above

Internet access to: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/galvan5.swf

4.2

Empowering Phase

Activity:

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Questions:

1. From the simulation, which electrode acting as anode? Which one is cathode?

2. What happens at anode and cathode during the process?

3. Write half equation take place at anode and cathode.

4. In what direction do the electrons flow?

5. What is the function of the salt bridge?

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Sample Answer:

1. (i) Anode – Zinc electrode

(ii) Cathode – Copper electrode

2. (i) Anode

Each zinc atom donates two electrons to form a zinc

ion. The zinc ions are released into the electrolyte.

The zinc plate dissolves gradually.

(ii) Cathode

The electrons released by zinc plate will be accepted

by copper (II) ions to form copper metal. The copper

plate becomes thicker gradually.

3. Anode : Zn Zn2+ + 2e

Cathode : Cu2+ + 2e Cu

4. Electrons flow from zinc electrode (anode) to copper electrode

(cathode).

5. Salt bridge allows the movement of the ions in order to complete

the electric circuit.

4.3 Enhancing Phase

Activity 1:

1. Students are divided into group of 5. Each group will be given a Worksheet 1.2. In group, by applying the concept which has been learned before,

students need to complete the Worksheet 2.3. Teacher acts as a facilitator, observing and correcting students’

mistakes while they are completing the worksheet.4. After finishing the Worksheet 1, each group need to present their findings in front of the class.

Activity 2 :

1. Students are divided into group of 5. Each group will be given a Worksheet 2.2. In group,by applying the concept which has been learned before,

students need to complete the Worksheet 2.3. Teacher acts as a facilitator, observing and correcting students’

mistakes while they are completing the worksheet.4. After finishing the Worksheet 2, each group need to present their findings in front of the class.

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WORKSHEET 1

Type of Cell Electrode Electrolyte Uses Advantage Disadvantage

…………………………………………………

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…………………………………………………

…………………………………………………

Type of Cell Electrode Electrolyte Uses Advantage Disadvantage

…………………………………………………

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…………………………………………………

WORKSHEET 2

Simillarties

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Electrolytic Cell

DifferencesVoltaic Cell

Energy change

Electric current and reaction

Cathode and anode

Flow of electron

Negative terminal

Positive terminal

ANSWER WORKSHEET 1

Type of Cell Electrode Electrolyte Uses Advantage Disadvantage

Carbon (+)Zinc (-)

Ammonium chloride paste

Torches Radio Electrical

toys Cassette

player

Portable Cheap

Not rechargeable

Short lifetime Low current Current drops

gradually discharging of electricity

Leakage of electrolyte

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…………………………………………………

…………………………………………………

Lead with lead(IV) oxide(+)

Lead plate (-)

Dilute sulphuric acid

Motor vehicles

Rechargeable

Large current

Voltage remain steady during discharging electricity

Not so portable

Bulky and heavy

Expensive

…………………………………………………

Mercury(II) oxide and carbon (+)

Zinc powder (-)

Potassium hydroxide paste

Camera Watches Calculator

Portable Small in

size Light Steady

current Longer

time

Not rechargeable

High cost

Type of Cell Electrode Electrolyte Uses Advantage Disadvantage

Manganese(IV) oxide (+)

Zinc (-)

Potassium hydroxide

Cassette players

Electrical toys

Portable Long

lifetime Large

current Voltage

remain steady during discharging electricity

Not rechargeable

High cost

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…………………………………………………

…………………………………………………

Nickel(IV) oxide (+)

Cadmium (-)

Potassium hydroxide solution

Cassette player

Electrical toys

Radios

Rechargeable

Portable Large

current

Expensive

ANSWER WORKSHEET 2

They consist of an electrolyte each

They consist of two electrodes each

The process of donation of electrons occurs at the anode while the process of acceptance of electrons occurs at the cathode

Electron flow from the anode to the cathode in the external circuit

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Simillarties

Electrolytic Cell

DifferencesVoltaic Cell

Electrical energy to chemical energy

Energy changeChemical energy to Electrical

energy

Electric current result in a chemical reaction

Electric current and reaction

Chemical reaction produces an electric current

Cathode : negative terminalAnode : positive terminal

Cathode and anodeCathode : positive terminalAnode : negative terminal

Electron flows from the positive terminal (anode) to negative

terminal (cathode)Flow of electron

Electron flows from the negative terminal (anode) to positive

terminal (cathode)

Cation receives electrons from cathode (negative terminal)

Negative terminalElectrons are released at the negative terminal (anode)

Anion released electrons to the anode (positive terminal)

Positive terminalElectron are received by the positive terminal (cathode)

5.0 Reflection

1. Teacher asks five students to give conclusions for the lesson.

2. So, we can conclude the simulation techniques which had been used throughout the teaching and learning process could effectively enable students to master the voltaic cell concept.

6.0 Reference

Voltaic cell, retrieved on 5 April 2013 from http://www.berryberryeasy.com

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Galvanic cell, retrieved on 5 April 2013 from ht t p: / /ww w .mhhe. c om / p h y ssci/c h e m i st r y /es s e nt ia lch e m i st r y /flash / g a lvan5 . swf

The Lemon Battery, retrieved on 5 April 2013 from ht t p: / /ww w . y outube. c o m /w a tch ? v = D X ir_ O RH O G A &f ea tu r e= r e lat e d

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