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