Peer teaching
Whitney Pye and Jessica Simms
ED 4174 – Lab: Peer teaching episode
Chemistry 3202- Unit 4: Electrochemistry
Prior knowledge: A fruit/vegetable battery is an experiment that many students will be exposed
to earlier in school. Many students will know what to expect and how it works, but they would
not have learned the specific chemistry behind the experiment. Furthermore, reduction and
oxidation reactions were covered only a few lessons prior to this lab, and solutions, ionization,
and chemical equilibrium were all studied in previous units of chemistry 3202. Students also
studied electronegativity in chemistry 2202.
Specific curriculum outcomes:
313-8: Select and use apparatus and materials safely.
322-4: Illustrate and label the parts of electrochemical and electrolytic cells and explain how they
Core lab outcomes:
213-8: Evaluate a personally constructed cell by selecting and using apparatus for
electrochemistry labs.
214-14: Construct and test a system and troubleshoot problems as they arise.
214-16: Evaluate a constructed galvanic cell.
214-18: Evaluate the relevance, reliability, and adequacy of data and data collection methods.
215-7: Evaluate processes used in planning, problem-solving and decision-making, and
completing a task.
Student learning goals:
-Students will label an electrochemical cell.
-Students will assess the roles played by each part within an electrochemical cell.
-Students will identify the half-reactions occurring at the anode and cathode.
-Students will synthesize information to determine that oxidation and reduction are taking place.
-Students will identify the direction of electron flow in an electrochemical cell.
Resources and materials used:
Lab activity (per group)
Large Potato
Two pennies
Two galvanized nails
Three alligator clips
An LED light bulb
A knife
Learning resources
Role playing activity
Chemistry 3203 unit 4 curriculum
Construction paper role cards
Exit Card (template:
Peer teaching
Lesson Plan: Creating galvanic cells with household items
Review safety procedures
1 minute
Teacher reminds students to be cautious
with wires and knives used during activity.
Students are listening.
Introduce electrochemistry
10 minutes Teacher is introducing the topic and relevant
information in the form of a brief lecture.
Students are listening and taking notes.
Build a potato battery
10 minutes Teacher explains activity then circulates
throughout the room offering advice and
engaging students in questioning.
Students build their batteries.
Students illustrate and label their 5 minutes
Students draw diagrams of the batteries they
just constructed.
Teachers continue circulating throughout
groups, offering help as needed.
Discuss redox equations
5 minutes
Teacher facilitates discussion.
Students discuss what redox reactions they
believe to be taking place during the
Role Play: electrochemical cell
5 minutes
Students role play the direction of electron
flow in a galvanic battery.
Teachers facilitate the activity.
Complete Exit Card
4 minutes
Students complete exit cards.
Teachers gather completed exit cards.
Total time: 40 minutes
Review safety procedures (1 minute):
Advise students to be careful when handling the wires as they will have an electric
current running through them. They must also be cautious when using the knives to cut
holes in the potatoes for the pennies.
Introduce electrochemistry (10 Minutes):
Teacher will introduce the following topics pertaining to the lab activity:
-The definition of an electric current
-How reduction and oxidation are necessary for the production of electricity
Electrochemistry: electrochemical (or galvanic) cells
-The necessary components in an electrochemical cell
-The necessary terminology:
-Electrodes: anode and cathode
-Anodic and cathodic ion solutions
-Anion and cation
-Salt bridge or porous barrier
-Other necessary components:
-Copper wire (or alligator clips)
-The direction of electron flow and ion migration
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Build a potato battery (10 minutes):
Students will construct their potato batteries with the materials provided by the teachers.
Teachers will circulate to assist students as necessary. Teachers will engage students with
questions about the theory behind the batteries. For example, do they think other
household items would provide similar reactions? What would happen if multiple cells
were added to the batteries? Why was a salt bridge necessary in the introductory lesson,
but there is no salt bridge when using the potatoes?
Students illustrate and label their batteries (5 minutes):
Students will draw diagrams of the batteries they constructed. The terms they must know
are illustrated in the curriculum guide:
-Salt bridge
-Direction of electron flow
-Direction of ion migration
Students must also be able to identify the anions (negatively charged ions) and cations
(positively charged ions).
Discuss redox equations (5 minutes):
Teacher will discuss the reduction and oxidation reactions that are occurring during the
experiment. Potatoes contain phosphoric acid (H3PO4) and water (H2O). The water
initially creates a slight polarity in the electrodes (the penny, constructed with Cu, and the
nail, which is coated with zinc oxide [ZnO]). Because acids tend to have easily
detachable hydrogen ions, which are positively charged, the ionic solutions also become
polarized. This enables an electrochemical, or spontaneous redox reaction, to occur
Peer teaching
between the copper in the penny and the zinc in the nail. The bubbles that form are a
result of the hydrogen gas that is produced.
The reactions occurring at the electrodes are as follows:
Zn  Zn2+ + 2e- [O] Anode
Cu2+ +2e-  Cu [R] Cathode
Electrons are flowing from the anode to the cathode because electrons are naturally
attracted to positively charged atoms. Anions (negatively charged ions) are migrating
toward the cathode, while cations (positively charged ions) are away from the anode to
maintain a balanced charge.
Role Play: Electrochemical Cell
Teacher will give directions to students about the role play and give them each a role to play in
the cell. Students should be able to show the movement of the electrons.
Complete Exit Card (4 minutes):
Teachers will provide students with Exit Cards to complete then gather them after students have
There are several types of activities incorporated throughout the lesson that address different
types of learning. Brief lecturing, experimentation and kinesthetic activities, as well as
discussions and questioning will provide students with a variety of learning opportunities.
Students will also have to draw and label a diagram of the experiment, and reflect on what they
learned throughout the lesson by completing the Exit Card.
-Assessment through observation during the role playing activity (students must have an
appropriate understanding of concepts in order to complete the activity successfully)
-Exit Card
Chemistry 3202 curriculum guide – Unit 4: Electrochemistry:
How to Make a Potato Powered Light Bulb:
Chapter 3: Electrochemistry: http://sci-toys.com/scitoys/scitoys/echem/batteries/batteries.html