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Lesson Write-Up for Spring Quarter 2012
Your name: David Luong, Albert Medina, Lynn Rice
Title of Lesson: Electrochemical Cells
Grade Level: 11th-12th
Subject(s): Physics, Chemistry
Summary:
This lesson is intended to introduce students to the fundamentals of electrochemical cells
governing the production of electrical potential or voltage. Electrochemical cells convert
chemical energy into electrical energy. Students are given a physical description analogous
to the production of voltage and current, the transport of charged particles. This
production process is covered in greater depth chemically in identifying the basic
components of an electrochemical cell: the anode, cathode, and electrolyte. Students are
tasked with creating various electrochemical cells with the metals and electrolytes
supplied to develop some insight into how the chemical composition of a battery
determines performance. Voltage is measured with the use of a multimeter. Finally,
limited by their single electrochemical cell voltage, students work as a class to create an
array of cells, or battery, electrically connected in series in an effort to increase voltage
output.
Time Required: 55 minutes
Group Size: 3-4 students per group
Cost to implement: ~$45 (for 8 periods of 30+ students)
 10lb bag of potatoes ($5)
 2 cups of lemon juice ($5)
 0.5 gallon of vinegar ($5)
 Electrode materials ($25)
o Copper
o Zinc
o Aluminum
o Steel
o Magnesium
o Tin
 (Reusable) condiment cups ($5)
Learning Goals:
After this lesson, students should be able to:
1. Cite components of an electrochemical cell
2. Cite functions of components of electrochemical cell
3. Discuss oxidation and reduction reactions: redox
4. Discuss electrochemical cell design considerations such as electrode combinations
5. Connect multiple cells in series to produce greater electrical potential
Level of Inquiry:
After students are comfortable with the mechanics of an electrochemical cell, they are left
to their own device to indirectly reconstruct the redox potential table. First they are asked
to use Copper as the mandatory cathode and test the remaining metals as the anode in the
electrolytes provided. Secondly they are asked to use Zinc as the mandatory anode while
the remaining metals act as the cathode. In this manner, students are able to observe the
electrical potential created from the various electrode combinations and discuss chemically
why certain combinations outperform others. Additionally, students will encounter both
positive and negative voltage measurements from their multimeter given the
cathode/anode specified above. They are to determine what these measurements imply
about the role each electrode assumes in the cell and the direction of current within the
circuit.
Introduction / Motivation:
Describe current and voltage with analogy to elevating a bucket of water (potential energy)
and pouring it to the ground (flow of current). Describe the induction of voltage and
current with two dissimilar electrodes connected with a wire and placed in an electrolyte.
Explain the responsible chemical reactions (oxidation and reduction) with the acronym “Oil
Rig” (oxidation is loss, reduction is gain) or “Leo says Ger” (lose electrons oxidation, gain
electrons reduction). Explain the procedure by modeling the steps. Provide a challenge to
the class that each group’s best batteries will be placed in series to light up the LED ladder.
Procedure:
1. Before the lab, the instructor should build the Bar Graph Meter on page 3 (typical
application) of the LM3914 datasheet. Choose R2 and R1 so that R2/R1 = 9. This
will ensure that students will need to collectively provide a 12V battery source using
their batteries to light up every LED.
2. Gather the electrolytes:
 Electrolyte 1: place vinegar in the container provided
 Electrolyte 2: cut a piece of potato
3. Attach the designated electrode to the multimeter terminal using an alligator clip
 Case 1: connect the copper cathode to the positive terminal of the multimeter
Case 2: connect the zinc anode to the negative terminal of the multimeter
4. Attach the remaining multimeter terminal to one of the specified electrodes using an
alligator clip:
 Case 1: lead, zinc, tin, magnesium
 Case 2: zinc, copper, steel, tin
5. Insert both electrodes in the electrolytes (first vinegar, then the potato), measure
the voltage produced and record results in the table below. Be sure the alligator
clips are not immersed in the vinegar or potato.r
6. Repeat steps 1-4 for case 2
7. Using alligator clips, have students connect their best batteries in series to the Bar
Graph Meter one at a time. Anode of one battery is connected to the cathode of the
next battery, so on and so forth. As more batteries are serialized, the more LEDs will
light up.
Materials List:
LED demo by instructor:
1. LED
2. Multimeter
3. Lemon juice
4. Strips of metal: Copper and Magnesium
Each group of students will need:
1. Multimeter
2. Alligator clips
3. Small cup or container
4. Potato
5. Vinegar
6. Labeled strips of metals: Copper, Zinc, Lead, Tin, Magnesium, Steel, Aluminum
LED ladder for class activity:
1. LEDs
2. Breadboard
3. Electrical wire
4. LM3914 Dot/Bar Display Chip
5. 9V battery
Safety Issues:
N/A
Lesson Closure:
In closing, students reflect on their cell configurations and reconstruct their most
promising electrochemical cell based on the greatest voltage achieved. It should be made
clear that although they were able to produce a finite amount of voltage, the cell still
remains largely impractical for useful applications. However, there is a way to boost the
voltage output using the very cells they just created. This is achievable by connecting
multiple cells in series, effectively creating a battery. Now as a class, students are asked to
add their cell one at a time to the series circuit to contribute to the voltage output. The
increase in voltage may be monitored by a multimeter with a large display or better yet a
light-emitting diode (LED) ladder. The LED ladder seed a line of LEDs with the number of
LEDs lighting up depending on the amount of voltage applied to the circuit. As the class
adds additional cells to the circuit additional LEDs light up accordingly.
Assessment:
Pre-Activity Assessment:
Ask students what they know about basic electrical terms such as voltage and current.
Make an analogy to potential energy by elevating a bucket of water and its gradual energy
loss as it gets poured.
Activity Embedded Assessment:
Students are given a worksheet where they are asked to fill in the blanks with answers
given from the pre-activity assessment.
Post-Activity Assessment:
Bring students back together and accept a battery from each group. Connect the batteries
in series one at a time, emphasizing the anode of one battery is connected to the cathode of
the next. While connecting, ask the class about their lab results.
 Which electrolyte worked best? Was it clear?
 What were signs that oxidation and reduction occurred?
 Why do you think batteries cannot last forever? Were there signs in the lab that
indicated this?
Is this lesson based upon or modified from existing materials? If yes, please specify
source(s) and explain how related:
References:
Attachments:
 Battery worksheet (Word)
 LM3914 Datasheet
List CA Science Standards addressed:
1. Electric Phenomena
2. Acids