GEORGE L. GILBERT Demon Unwersrty Granv4e. Ohm 43023
The demonstration presented in this issue is an example of a Corridor Demonstration. This tvne of demonstration or exhibit can he set up in a hallway, lobby or other readily accessible area. Some exhibits or demonstrations may he of sufficient general interest to warrant their display in a more central area such as the Student Union in which case alternating with other departments might prove a reasonable pattern. The demonstration should present or illustrate a particular concept or series of facts-or pose questions for consideration an4 response. It can be, in the opinion of this editor..averv effective teachine aid. Corridor demonstrations ~. . have not been used totheir full-potential, and we are soliciting descriptions of such demonstrations for inclusion in this column in an effort to circulate information to those who are interested in this techniaue hut who are not sure of how to begin. Hopefully, this wiil inspire more contributions and a supplv of ideas will be available which will helo to avoid the often-noted pattern of an exhibit being set np'and then left too long due to a lack of follow-up ideas. Corridor exhibits come inmany varieties: some of the ones I have learned about are detailed below. " A
Interactiue Exhibits. Interactive exhibits allow the viewer to cause some change in the exhibit by pressing a button, turninz a handle or some other action. Descrintive information relating to the observations possible upon cknpletion of the action sten allow the desianer to chance the exhibit to empl,;~sizedi'fferrnr pr,itm ( 8 ; t o d i n m th; l d m i ruuurd a part icular audience or {In;. 'l'l~etnmr so~hist~t:ited and complex systems use up the materials invoived and hence require continued monitoring and renewal, putting them beyond the scope of most academic institutions. Such exhibits have been developed and used extensively in Science Centers or museums. 'l'he heavy uwye uf rhc exhibi~iin 'icience Centers u.ith its w n m m i t ~ ~ nrequlrrmrnt r ot'durnhle rquipment and materials is less of a nroblem a t academic inst&tions. Selection of equipment and its means of access by the user must be made carefullv lest damaae of exoensive annaratus andlor where access is limited while retaining control for the user. One modest example is offered in the accompanying article. Changing Exhibit. The use of an exhibit area to introduce a series of materials over an extended period of time promotes continued interest in the area while offering a way to develop a tonic through incremental changes. The use of timelv queskms or presentation of materiais to solicit interest in an awareness of the roles of chemicals in our lives is shown in the second article in this series. Challenging Exhibits. A demonstration or set of apparatuses which noses auestions and solicits resnonses can nrodnce stimulating discussion and creative thinking on the part of both local viewers and visitors to the department. Concepts in Exhibits. Another use of exhibit areas is for the display of materials pertinent to topics under discussion in courses currently being taught. One example is a colorful arrangement of the various oxidation states of elements in commercially available compounds as well as locally synthesized compounds. Exhibits which periodically focus on im216 1 Journal of Chemical Education
portant scientific theories and concepts and their authors also provide interesting ways to utilize exhibit areas in chemistry buildings. The opportunity to participate in supplying andlor testing Corridor Demonstrations is extended to each reader. Your continued suonort of this column and the active assistance of both a u t h ~ r ~ a ncheckers d is appreciated. Tested Demonstrations Editor
Corridor Demonstration Electrical Energy from Cells-A Demonstration
Corridor
Three cells which develop electrical energy are constructed to allow demonstration of the availability of power from various types of cells. The information which accompanies each cell, in addition to the directions given for its use, can he changed to focus on different aspects of the system, e.g., to focus on comparative economics, power per pound, etc. Thus changing dgcriptive material alters the direction and function of the demonstration. The arrangement used can he adapted to local space and equipment options and the information and equipment designated should he considered one possible system among many which can be developed. The equipment used in the display assembled is listed below: 1) Solar Cell 1. A solar cube (Edmund Scientific # 42,711-($24.95)) 2. high intensity lamp 3. push-buttonswitch for 110 V 4. power card 2) Lead and Fuel Cells 1. Five-oosition switch (CentralabPA2007) 2. ~ h r e kpush-button switches-one for 11'0 V 3. Power supply (require 7vDC)-used Lab Volt Model 187P 4. Power cord 5. Solar cell motor (Edmund Scientific # 40.872 $4.95) + (paper propeller) 6. VTVM-used Heathkit Model EUW-24-(need 0-5 V scale, high impedance) 7. 4 alligator clips, various colors of covered wire 8. control panel for mounting switches 9. external power eord-with receptacle for 3 plugs 1. 1 liter beaker 2. 2 large lead electrodes-2 ih. X 8 in. X 118 in. 3. cork stopper to fit beaker, cut slots to support lead elee-
4)
Fuel Cell 1. 2 carbon rods-8 in. long 2. 1liter beaker 3. cork stopper to fit beaker-bore two holes to support carbon mrl-
4. 6 M H~SOI-800 ml
The system was assembled according to the diagram below
?k& CELL
The cards used in this display as presented at the Fifth Biennial Conference on Chemical Education, Fort Collins, Colorado, are shown below.
LEAD
This commerciillly important c e l l find. its m a j o r application i n l u t o m o b i l e s
and r t q u l r e s
e * c e s r ol 100,000 tons of lead annually < o r production of t h e
electrode p h t c a . ELECTRICAL
ENERGY
FROM
CELLS
CELL
The MparIanf rhcmical reactions during c h a r g e and
discharge are: pb
+
PbOL + 2H2S04
discharge
ZPbS04
+ 2Hi0
charge
SOLAR CELLS
-
2 volts
To:
Turn the muiripoaition awltch t o C , p i e r s both the lead c e l l and charge buttons f o r 1 5 - 3 0 reconda.
To Diarhar..:
(a) To ~ ~ c r a ,he t . motor t u r n the s w i t c h t o positlo" B, ,b) To .,hain ,he output "drag. on the voltmeter t u r n the switch t o position A.
FUEL C E L L S STORAGE CELLS (BATTERIES)
FUEL
CELL
A hydrogen-oxygen fuel c e l l which o b t a i n s its fuel from e l c c t r o l y r i s of w a t e r and h a s l i m i t e d c a p a c i t y i n the p o r o u s c a r b o n rod..
Reactions:
SOLAR C E L L --
:
Turn the m u l t i p o s i t i o n s w i t c h fa C, p r e s s both the f u e l c e l l and c h a r g e buttons f o r 15-30 seconds.
To Discharp:
(a) To o p e r a t e the m o t o r turn t h e switch t o p o s i t i o n D.
Sillcmn n / p type c e l l with m a x i m u m output of 0. 4 5 v o l t s at 225 m A
(b) T o read the-output
- p o w e r of
100 m ~ / c m ~
voltage on the voltmeter turn
the s w i t c h to position E.
To Oqeratc: Press b u t t o n m a r k e d SOLAR C E L L
Volume 57. Number 3, March 1980 / 217
