Chemistry for Everyone
W
Chemistry at a Science Museum Robert G. Silberman* and Charles Trautmann Sciencenter, 601 First Street, Ithaca, NY 14850; *
[email protected] Susan M. Merkel Department of Microbiology, Cornell University, Ithaca, NY 14850
Chemistry tends to be one of the least represented sciences at science centers and museums around the country. Perhaps it is because chemistry exhibits use up chemicals, require frequent monitoring, and present potential safety issues. Most exhibits focus on either physical analogies for physical chemical processes, or look-but-do-not-touch exhibits in glass cases (1). In recent years some science centers have begun to experiment with simple, interactive floor activities involving chemistry. These usually take the form of very short, safe, laboratory-type activities that can be tried by visitors at a supervised table or counter. The advantage is that museum visitors actually get to work with chemicals and experience the fun of trying out chemical reactions or solving simple chemical puzzles. After retiring from teaching college chemistry, one of the authors (RGS) coauthored a proposal with the Sciencenter to the Dreyfus Foundation titled “The Chemistry Investigators—Interactive Chemistry Programs for Museum Visitors”. The goal was to develop several simple activities in which children got to investigate the properties of chemicals to solve simple puzzles or challenges. The Sciencenter is a hands-on science museum located in Ithaca, New York with the mission, “to inspire people of all ages and backgrounds to discover the excitement of science through programs and exhibits that promote learning through interaction”. Founded in 1983, the organization provides engaging and inspirational science experiences for families and school groups throughout upstate New York and beyond. The community-built museum facility, constructed in 1993, has won national acclaim for its exhibits and programs, and currently serves over 75,000 visitors annually. The typical visitor to the Sciencenter is a 4–10-year-old child with accompanying adults.
for activities requiring comparisons of chemical reactions, The Fruit Juice Mystery and Which Powder Is It?, a plastic laminated grid worked better than a wellplate, because laminated sheets could be easily labeled. We began by trying out each activity with two or three children before moving to the museum floor with a larger group. Fortunately, one of the authors (SMM) had children of the appropriate age, seven and ten years old, to be our testers. In the original proposal the suggested activities were derived from the high school chemistry curriculum (1) and a lab manual from a nonmajors college course (2, 3). We quickly found that activities that took longer than a few minutes, required multiple tasks, or did not have something unexpected happening immediately were not successful. We concluded that our activities had to involve some indication that something happened when chemicals were mixed. A color change, gas evolution, precipitate formation, or a temperature change was an essential ingredient in each successful activity. Measurement activities had to involve an obvious change such as a rapid temperature change, sounds, or lights. With this in mind most of our activities were derived from chemical demonstrations rather than laboratory experiments (4, 5). Whenever possible, we tried to use familiar household chemicals. We did not set out to teach specific chemical principles. Our goal was to have activities that enabled visitors to experience the fun of chemistry investigations. Each activity has a simple question that can be answered by “messing around” with chemicals in a controlled way. In a sense, each activity is a child-sized, 5–10 minute research problem. Children are told what the challenge is, given safety goggles, shown the equipment, given the solutions in clearly labeled color-coded dropping bottles, and then set to work.
Considerations for the Activities
Evaluation of the Activities
Working with young children on a museum floor presents a number of challenges. Chemicals have to be safe (i.e., relatively nontoxic, nonflammable, and noncorrosive). This effectively eliminates strong acids and bases, heavy metal ions, and most organic solvents. The equipment has to be very simple (i.e., no stirrers, hotplates, or burners, and minimal glassware). Everything has to be tested—even simple supplies often present unpredictable problems. For example, soon after we began using transfer pipets and wellplates, we found that they did not work well. Young children, five and six years old, had trouble squeezing out single drops from transfer pipets. Older children found that pipets could be used as squirt guns. The solution was to switch all liquids to 30-mL or 60mL dropping bottles that allowed only a drop at a time to be squeezed out. The young children could use both hands to squeeze out a drop and the older children could not squeeze out more than a drop or two at a time. We also found that
Since this was not a classroom setting it was difficult to evaluate the success of each activity in an objective way. No child at a museum is willing to fill out a questionnaire or take a test. Our criteria for evaluating an activity depended on observing the time children spent doing the activity. The average time spent at a museum exhibit by a young child is measured in minutes or even seconds. A successful activity engaged a child for several minutes until they completed the activity. Children simply left if an activity did not interest them. If a child ran to get a friend to try the activity or the child came back and asked to try it again, we thought this was an indicator of a successful activity. Many of the children seemed fascinated by the activities and played around with the chemicals trying to find out what else could happen when the chemicals were mixed. Since no combination of chemicals in any given activity would react in a dangerous way, we encouraged the children to experiment.
www.JCE.DivCHED.org
•
Vol. 81 No. 1 January 2004
•
Journal of Chemical Education
51
Chemistry for Everyone
The Activities Ten activities were developed for the Sciencenter. Each activity is described briefly below and in more detail in the Supplemental Material.W Each activity is presented as a challenge.
Carrying Charges The challenge: Can you make a solution that conducts electricity to make the buzzer buzz? Visitors worked with water, salt, sugar, salad oil, rubbing alcohol, and vinegar to discover which liquids or solutions conduct electricity and make a simple conductivity detector buzz (6, 7). Changing Colors The challenge: Can you make the solution change from colorless to yellow to blue, then back to colorless? Visitors work with dilute solutions of bleach, sodium thiosulfate, potassium iodide, soluble starch, and water that, if added in the correct order, produce the colors indicated. Fruit Juice Mystery The challenge: Can you discover which juice is a fake made from food color, water, and sugar? Visitors work with several fruit juices, vinegar, and dilute washing soda (sodium carbonate) solution to discover which one is artificial. Cranberry juice, grape juice, and blueberry juice act as pH indicators, changing colors when vinegar or washing soda is added. Fake juice made from food color does not. Liquid Rainbow The challenge: Can you create a rainbow pattern of colors in a test tube? Visitors are given a series of colored ethanol/ water solutions, each with a different density. By slowly adding the solutions to the same test tube, they determine the order of density. By adding the solutions in order of density, visitors can create a rainbow effect in a small test tube. Plant Power The challenge: Can you find which plants have an enzyme called catalase that breaks hydrogen peroxide into water and oxygen? Visitors work with 3% hydrogen peroxide and several different fruits and vegetables, both raw and cooked, to determine which ones have the enzyme. Disappearing Stains The challenge: Juice spilled all over a new shirt and you are in big trouble. Can you make the stain go away before you get busted? Visitors find out what will remove the stain by mixing a series of cleaning solutions (vinegar, dishwasher detergent, or dilute bleach) with juices. Visitors then predict which solution will best remove the stains from a cloth. Which Powder Is It? The challenge: Can you distinguish between white powders found in the average household? Visitors do a series of simple chemical tests with three white powders. Each powder reacts differently with three reagents. They then use their observations of the results of the chemical reactions to determine which powder of the three is in an unlabeled container. 52
Journal of Chemical Education
•
Hot and Cold The challenge: Can you find the combination of chemicals that could be used to make an instant cold pack? Visitors combine chemicals in a simple calorimeter and use a small thermometer to determine whether the reaction mixture becomes hot or cold. [Editor’s Note: See pages 64A–64B for the JCE Classroom Activity based on this activity (8).] Finding Colors The challenge: Can you find five indicator colors (red, orange, yellow, green, and blue) when an acid and a base are reacted together? Visitors work with vinegar, a dilute solution of washing soda solution, and Bogen’s universal pH indicator. If the acid is neutralized a little at a time the indicator will show several colors as the pH changes from acidic to basic. Finding Red The challenge: Can you find which solutions, when mixed, produce a red-colored mixture? Visitors work with dilute solutions of ferric chloride, oxalic acid, potassium thiocyanate, and tannic acid to find what combination of two solutions produces a red mixture. If more than two solutions are mixed, visitors discover that colors can be made to appear and disappear. Hazards Most of the chemicals used in these experiments are nontoxic household chemicals. Sodium thiosulfate, ammonium thiocyanate, tannic acid, and oxalic acid are slightly to moderately toxic by ingestion. Ammonium nitrate is a strong oxidizing agent and can decompose violently if heated strongly. Bleach (5% sodium hypochlorite solution) and 3% hydrogen peroxide are eye and skin irritants. Ethyl alcohol is a flammable liquid and should be handled and stored accordingly. Logistics of the Activities At the Sciencenter the entire program is run by a single retired chemistry professor who volunteers his time (RGS). College or high school student volunteers present almost all of the chemistry activities to visitors. Because these activities involve relatively simple chemistry, student volunteers with a single high school or college chemistry course can be easily trained to do these activities with visitors. Training sessions usually involve several volunteers in each session. A typical training session lasts 15–30 minutes and involves a safety discussion, a demonstration of the activity, a review of the chemistry, answering questions, and a trial of the activity. Volunteers are informally monitored the first few times they do the activity. There is no set schedule for doing the activities. In a typical week there will be 8–10 hours of chemistry activities. The activities are presented when volunteers are available to do them with visitors. Not all the activities are done in a typical week. Those activities that require more extensive preparation or unstable solutions, “Plant Power” and “Changing Colors”, are done infrequently. Usually the activities are done at the Sciencenter’s designated demonstration area. However, we have also done the activities at a table on the museum floor. On occasion, the Sciencenter plans a chemistry day during which most of the
Vol. 81 No. 1 January 2004
•
www.JCE.DivCHED.org
Chemistry for Everyone
activities will be set up at various stations on the museum floor. The chemistry day also includes a chemical demonstration show. All the supplies, chemicals, and equipment for a given activity are stored in a large labeled plastic storage container. Each labeled container contains a detailed plastic laminated set of directions for the activity. The containers are stored near our demonstration area. Each container has a sign-out sheet attached that asks for the volunteer’s name and a list of chemicals or other supplies that are running low in the kit. The containers are checked on weekly basis and the needed chemicals and supplies are replenished. Stock solutions of all stable solutions are maintained in a separate chemical preparation and storage area. Although these activities were developed for a museum venue, one reviewer correctly pointed out that the activities are also well suited for a chemistry day, chemistry outreach, or an enrichment program. Acknowledgment Support for this project was provided by The Camille and Henry Dreyfus Foundation’s Special Grant Program in the Chemical Sciences. We thank them for their support.
www.JCE.DivCHED.org
•
W
Supplemental Material
Detailed descriptions of each activity are available in this issue of JCE Online. Literature Cited 1. Ucko, D. A.; Schreiner, R.; Shakhashiri, B. Z. J. Chem. Educ. 1986, 63, 1081. 2. Ehrenkrantz, D.; Mauch, J. J. Chemistry in Microscale; Kendall兾Hunt: Dubuque, IA, 1996; Book 2. 3. Silberman, R. G.; Stratton, W. J.; Bunce, D. M.; Schwartz, A. T.; Stanitski, C. L.; Zipp, A. P. Chemistry in Context Laboratory Manual, 2nd ed.; American Chemical Society: Washington, DC, 1997. 4. Summerlin, I. R.; Ealy, J. L. Chemical Demonstrations, 2nd ed.; American Chemical Society: Washington, DC, 1988; Vol. 1. 5. Summerlin, I. R.; Borgford C. L. Chemical Demonstrations, 2nd ed.; American Chemical Society: Washington, DC, 1988; Vol. 2. 6. Ehrenkrantz, D.; Mauch, J. J. Chemistry in Microscale; Kendall兾Hunt: Dubuque, IA, 1996; Book 1, p 106. 7. Gadek, F. J. J. Chem. Educ. 1987, 64, 628. 8. Silberman, R. G. J. Chem. Educ. 2004, 81, 64A–64B.
Vol. 81 No. 1 January 2004
•
Journal of Chemical Education
53
