tugasan 5 voltaic cell
DESCRIPTION
Tugasan 5 Voltaic Cell (3E)TRANSCRIPT
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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