Electrochemistry
Bruce Kitsuse Peirce School
1423 W. Bryn Mawr Avenue
Chicago IL 60640
(312) 534-2440
Objectives:
Students understand that electricity causes chemical reactions and chemical
reactions can cause electricity.
Materials needed:
This list of materials is for three groups consisting of four members per group.
1. 1 Molar Copper Nitrate Solution
2. 1 Molar Zinc Nitrate Solution
3. 1 Molar Ammonium Nitrate Solution
4. 10 pieces of zinc metal
5. 10 pieces of copper metal
6. alligator clips
7. ten 300 ml glass beakers
8. masking tape
9. six stainless steel electrodes
10. box of epsom salt
11. six 6-volt batteries
12. insulated copper wire and wire stripper
13. six micro scale test tubes
14. matches and wood splints
15. paper clips
16. glass U-tube
17. cotton
18. voltmeter
19. buckets
Strategy:
Students will attain the objective by verifying the definition of
electrochemical cell through experimentation in a quiet, calm atmosphere.
Discipline will be achieved through a set of rules with consequences for
misbehavior.
The necessity of verification will be demonstrated through the use of newspaper
and magazine articles which are subjective as opposed to factual. These
articles will show that not everything we read is necessarily factual. It will
set up the need to verify the definition of electrochemistry and electrochemical
cell.
"Electrochemical Cell" will be defined as an "apparatus that utilizes an
electrolyte and electrodes in such a way that a chemical reaction will produce a
current sent through an external circuit."
Part of verifying the entire definition will be to define some of the words.
Electrolyte is a liquid conductor that utilizes dissolved particles to conduct
electricity. Students will make copper nitrate and zinc nitrate by combining
measured amounts of copper nitrate and zinc nitrate crystals with water. Prior
to combining, they will test the conductivity of the solid crystals with a
voltmeter. After making an aqueous solution, they will test the conductivity of
the solution. Students will return to their seats to discuss their
observations. The electrolytic solutions will remain at their stations for use
in further activities.
Redox reaction will be defined as a gain and loss of electrons (oxidation and
reduction). The example of table salt formed from the ionic transfer of
electrons from sodium and chlorine will be used as an example of spontaneous
gain and loss of electrons. Students will then verify that redox reactions
exist by placing a strip of zinc metal into copper nitrate solution. They
should observe the formation of copper and the corrosion of zinc metal. (Beakers
of copper nitrate, alligator clips, and zinc strips will be passed out to three
groups of four members each by teacher assistants. Discussion will occur in
these groups. Discussion will focus in what redox reaction has occurred. The
formula will be placed on the board before and during the activity. Students
will be asked to explain the formula and their observations.)
Students will then create a current by a redox chemical reaction by placing a
zinc strip into zinc nitrate and a copper strip into copper nitrate. They will
place one voltmeter electrode into the zinc nitrate solution and the other
voltmeter electrode into the copper nitrate and note that no current was
produced. A U-shaped tube will then connect the electrolytic solutions in the
two beakers. The zinc and metal strips will be connected by alligator clips to
the voltmeter and a current will flow. Overhead transparencies will be used to
demonstrate the directions. The formula for the chemical reaction will be
placed on board prior to and during the activity. At the end of 5 or 10
minutes, students will return to their seats and discuss their observations and
explain the formula.
Next, students will do electroplating. In this activity, the reversibility of
electrochemistry will be seen because a current will cause a chemical reaction.
The reaction will be that a copper strip is placed in copper nitrate solution
and a paper clip is placed in the same solution. Both the copper strip and
paper clip will be attached to wires which are hooked to the positive and
negative electrodes of a battery (these instructions will be shown on an
overhead projector.) The formula of the reaction will be shown prior to and
during the activity. Students will be asked to explain both the formula and
their observations upon completion of the activity.
Finally, students will perform the electrolysis of water with a similar
evaluation method.
Performance Assessment:
For most activities a formula of the expected reaction will be written on the
overhead projector prior to and left there during the activity. The students
comprehension of the activity will evaluated orally through their ability to
explain both the formula and their observations.
Conclusions:
Students should understand that electricity can be produced by chemical
reactions and chemical reactions can produce electricity because they have seen
this happen in the activities they performed. They should also understand that
in each case a redox reaction has occurred.
Evaluation:
Activities occurring in a science laboratory should be conducted under safe,
calm conditions. The learning atmosphere will be evaluated and monitored
constantly by the instructor. Movement of students from lab stations to normal
seating will be especially scrutinized. A worksheet with written comprehension
questions which should be filled out during the activities will help to assess
student learning. Discussion of observations will provide the most direct
information as to what was understood.
References:
Dorin, Chemistry, The Study of Matter, Allyn and Bacon
Williams, Chemistry Research Activities, Grolier Educational Corporation
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