Exploring Matter: An Interactive, Inexpensive Chemistry Exhibit for

Despite its vital importance in our lives, chemistry is inadequately represented in most museums. Issues such as safety, replenishing and disposal of ...
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Exploring Matter: An Interactive, Inexpensive Chemistry Exhibit for Museums Steven Murov*,† and Arnold Chavez‡ †

Science, Mathematics, and Engineering Division, Modesto Junior College, Modesto, California 95358, United States Great Valley Museum, Modesto Junior College, Modesto, California 95358, United States

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ABSTRACT: Despite its vital importance in our lives, chemistry is inadequately represented in most museums. Issues such as safety, replenishing and disposal of chemicals, supervision required, and cost are constraints that have limited the number and size of chemistry exhibits. Taking into account the constraints, a 21-station interactive and inexpensive chemistry exhibit has been designed, constructed, and installed in the Great Valley Museum on the Modesto Junior College West Campus. The exhibit is intended to stimulate interest in chemistry, demonstrate and emphasize the importance of chemistry in our lives, and provide a meaningful and enjoyable educational experience with chemistry. The centerpiece of the exhibit involves the identification of 11 elements from observations of relative density, electrical conductivity, magnetic properties, color, and luster. Descriptions of the 21 stations are included in this paper. KEYWORDS: General Public, Public Understanding/Outreach, Hands-On Learning/Manipulatives, Inquiry-Based/Discovery Learning, Drugs/Pharmaceuticals, Magnetic Properties, Periodicity/Periodic Table, Physical Properties

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CHEMISTRY EXHIBIT OVERVIEW

EXHIBIT STATIONS Currently the exhibit consists of 21 stations with varying degrees of interactivity and some hands-on experiences. Stations 1−12 primarily involve exploration of the properties of matter with an emphasis on density. Stations 13−15 include three problem solving challenges. Stations 16−20 cover chemical and nuclear reactions and relevant chemistry such as drug design and, very importantly, climate change. Consistent with the goal of improvement, Station 21 is a suggestion box. Many stations use inexpensive and commercially available materials. However, the more inventive Stations 11−14 and 16−20 require construction or unusual applications of commercially available materials. A brief description of each station is provided. Extensive details on presentation, materials, and design of each station are available online.6

Chemistry is often and appropriately described as “the central science”.1 To increase public understanding of crucial societal issues, chemistry needs and merits first-rate representation in science and natural history museums. However, as Ruth Jarman has pointed out, “Chemistry often loses out to physics and biology in science centres and science museums. This is because the subject can be challenging to present in an engaging fashion in these settings.”2 Consequently, chemistry is inadequately represented in most museums. Issues such as safety, replenishing and disposal of chemicals, supervision required, and cost are constraints that need to be considered in the design and planning of a chemistry exhibit for museums. These issues and ideas for chemistry exhibits have articulately been discussed previously.3 An American Chemical Society Collaborative Opportunities Grant4 coupled with a Modesto Junior College Foundation grant5 has enabled the Modesto Junior College’s Great Valley Museum to design, construct, and install an interactive and inexpensive chemistry exhibit, Exploring Matter. The exhibit is intended to stimulate interest in chemistry, demonstrate and emphasize the importance of chemistry in our lives, and provide a meaningful educational experience with chemical properties and reactions. The exhibit is pictured in Figure 1. The grant funds totaled $3200 and were used solely for the purchase of materials and display design. The exhibit should be considered a project in process, as it will be updated and improved as visitor response is evaluated. © XXXX American Chemical Society and Division of Chemical Education, Inc.

States of Matter

Stations 1 and 2. Stations 1 and 2 introduce states of matter and changes of state. Station 1 in its simplest form is a photo of six test tubes containing the solid and liquid states of substances (see Figure 2). Only for water does the solid float, but astonishingly, most people have never seen the solid and liquid states of single substances together, other than for water. As a result, without questioning, people accept the anomalous behavior of water as the norm even though it is extremely unusual.7 If supervision is available, the experience can be upgraded by partially freezing p-xylene and comparing the Received: January 5, 2017 Revised: August 17, 2017

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Figure 1. (left) Chemistry exhibit showing 20 of the stations installed on 30 ft. of linear bench space. Over 40 ft. of space would be preferred. To the left of the periodic table, photographs on the wall feature scientists who have contributed to many scientific milestones; chemists in particular are featured on the right. (right) An original mixed-media painting of Charles Darwin by Carolyn Murov displayed on the far wall (reproduced with permission).

4 is a weather station11 that through the use of the liquid crystal displays enables visitors to determine the temperature, humidity, and barometric pressure at several locations in and near the Great Valley Museum. Elements, Compounds, and Mixtures

Station 5. Station 5 has encased samples of a small selection of elements, compounds, and mixtures. The bismuth crystal alone receives awed attention from visitors.12 It is interesting that most museum visitors have probably never thought about the relationship (or lack thereof) between compounds and the elements that compose them. To develop this concept, samples of iron, sulfur, and attention-grabbing iron pyrite are included. Even observational evidence indicates that the properties of iron pyrite are not related to the properties of iron or sulfur. The choice of iron pyrite was dictated by the lack of availability of a more common compound such as sodium chloride and its elements (sodium and chlorine are not easily exhibited). Station 5 also introduces ferromagnetism by having visitors test the response of iron filings to magnets in clear, sealed containers13,14 and in a concentric cylinder.15 Station 5 has different kinds of mixtures, including a sealed bottle with water and 1-pentanol. Visitors are encouraged to shake this bottle and observe the behavior of immiscible liquids. As discussed in Observations and Conclusions, a toxicity exhibit could be a valuable addition to this station.16 Station 6. Paper chromatography is commonly included at family science nights and provides a hands-on experience at Station 6. For optimal results, solvents that include alcohols and ammonia are often used. To avoid smelly and toxic solvents, only water is used in this exhibit. Chromatography paper is consumed by this experiment, but Sargent Welch does stock a relatively inexpensive brand that gives adequate results.17 While PaperMate felt-tip pens provided some interpretable results, Expo Vis-a-vis wet-erase pens gave more interesting although not ideally resolved chromatograms. For chambers, cut-off

Figure 2. Image for Station 1. Test tubes containing the liquid and solid states of six substances at their melting points (from left to right): acetophenone (20 °C), dioxane (12 °C), water (0 °C), p-xylene (14 °C), acetic acid (17 °C), and oleic acid (14 °C).

system to an ice−water system. However, this interest-adding feature requires frequent attention because of melting of the ice and the solid p-xylene. Station 2 is a heat engine called a “drinking bird”.8 Although the explanation for the repeated action of the bird is complex, the evaporation of water from the bird’s beak is part of the process.9 Stations 3 and 4. Stations 3 and 4 strive to expand on the common visitor conception that there are three states of matter. Plasmas and dark matter are briefly mentioned in the Station 3 discussion. Although almost everyone has observed liquid crystal displays, most do not recognize liquid crystals as another state of matter. At Station 3 visitors observe that the color of a liquid crystal is affected by the warmth of their hands.10 Station B

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plastic peanut butter containers or inexpensive colorless plastic glasses have satisfied our requirements, with the paper suspended in the water by a large paper clip on a pencil mounted across the mouth of the vessel. Mass, Density, and Buoyancy

Stations 7 and 8. Stations 7 and 8 provide scales that visitors are encouraged to load and read. Because most visitors do not have much of a feel for the metric system, both of these stations have been designed to give visitors a sense of gram quantities. Visitors are asked to rank the masses of a rubber stopper, cork ring, and ball bearing by using their hands.18 Usually, most visitors rank them from lightest to heaviest: cork ring, rubber stopper and ball bearing. Afterward, visitors place each object on the scale and most find out that contrary to their estimates, the cork ring is the heaviest object. Use of the hand probably gives a measure of mass/area or pressure, leading to the incorrect ranking. Discrepant events usually attract attention and reinforce learning. In Station 8, several pennies are weighed. A penny weighs about 3 g, giving visitors another sense of the magnitude of gram quantities. Visitors discover that the pennies fall into two groups, with pre-1982 pennies weighing about 3.1 g and post-1982 pennies about 2.5 g. The difference resulted from a change from copper pennies to copper-coated zinc pennies.19 Thus, weighing a penny gives some information about minting date and penny composition. More details on penny experiments are available.20 Station 9. Station 9 contains four commercially available density-related items intended to arouse curiosity: a Galileo thermometer, a hydrometer, a liquid motion bubbler, and a density bottle. The reading on a Galileo thermometer depends on the temperature dependence of the density of the liquid. The hydrometer provided is used to determine the density of water. The value very close to unity demonstrates one of the huge advantages of the metric system over the American customary system. The liquid motion bubbler21,22 is closely related to the classic lava lamp and is based on the behavior of immiscible liquids with similar densities. The density bottle can be purchased23 or constructed24 and fosters interesting densityrelated questions. Station 10. Sink or float experiments have been proven to be popular.25−27 At Station 10, visitors examine a water tank about half full of water containing unopened cans of Pepsi and Coca Cola and their diet versions and observe that the regulars sink while the diet versions float. Asked why, some will correctly conclude that sugar makes the density of the regular drinks higher than that of water. Because artificial sweeteners are hundreds of times sweeter than sugar, much less is required, and the density of the diet cola cans is less than the density of water. For those that want to go further, it is possible to demonstrate the surprising fact that a bowling ball will float if it has a mass less than about 11 lbs. Heavier ones are denser than water and sink. Given the diameter of a bowling ball and the formula for the volume of a sphere, visitors can be asked to calculate the maximum weight a bowling ball can have and still float.

Figure 3. Scales for Stations 11 and 12 read out the mass of 12 cylindrical element samples. A magnet placed over the acrylic cover significantly changes the mass readout of the Ni and Fe cylinders.

Station 11 has 11 cylinders29 (1 in. × 1/2 in.; a 12th cylinder is used at Station 12) preloaded on tared scales. Since all of the samples are the same size, the mass readings are proportional to their densities, enabling a ranking of the 11 samples in order of increasing density. To provide a wide variety of elements, three of the elements included are nonmetals (C, S, and Se). Apparently, these samples are not firmly compacted, and their densities are lower than the literature values. In addition, two of the closely ranked metals as measured are in an inverted order. For this reason, a chart with “Great Valley Museum densities” that lists the densities as measured for our samples is provided to visitors.30 In addition to relative densities, visitors also qualitatively determine which (if any) of the samples are ferromagnetic as well as the electrical conductivity (with an accompanying ohmmeter and light-emitting diode (LED)), color, and luster of each sample. The possibility of ferromagnetism is determined by passing five stacked neodymium magnets31 (or a neodymium bar magnet) over the top of the Plexiglas. For any sample that is ferromagnetic, the reading on the scale significantly decreases.32 To determine the optimum height, the five magnets were placed over the cylinders until the mass drop for the ferromagnetic metals was about 3 g while the change for the nonferromagnetic materials was less than 0.1 g. This resulted in a box height of about 4.2 in.. The color and luster can be observed either in the acrylic case or in the electrical conductivity device. Combining all the observations, visitors should be able to correctly assign the identities of all 11 of the previously unknown elements. For the determination of electrical conductivities, strips of the elements were purchased33 and wired to a 12-position selector switch.34 Also included in the circuit is a 20 Ω digital meter35 and an LED (Figure 5). The meter essentially reads zero resistance except for carbon, selenium, and sulfur. Selenium and sulfur do not demonstrate any measurable

Identification of Elements

Stations 11 and 12. The centerpiece of the exhibit involves the identification of 11 elements designated by 11 colored squares in a large periodic table poster (Figures 3 and 4). Station 11 is contained primarily in a 2 ft. × 4 ft. wooden case containing 12 electronic centigram scales powered with USB cords28 and covered with a 1/4 in. thick sheet of Plexiglas. C

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Figure 4. Periodic table with the 11 elements for Station 11 in colored boxes.

mechanism. Often explanations include the word vibration. An external magnet can be used to demonstrate that the Tefloncoated bar contains a magnet. It is also interesting to ask why the magnet is coated with Teflon or, even better, what properties the plastic that is used to coat the magnet should have. Station 15. Most people have noticed the apparent bending of an object when it is partially immersed in water. Station 15 has two sealed plastic bottles. Each contains a Pyrex stirring rod and a Pyrex test tube. Water fills half of one bottle and glycerin half of the second bottle. Because Pyrex and water have significantly different refractive indices, the glass is easily visible in the water bottle. However, Pyrex and glycerin have very similar refractive index values, and the Pyrex objects are very difficult to detect below the liquid level in the glycerin bottle.

conductance, and the conductance of carbon depends on the nature of the carbon sample but is generally measurable. Station 12 involves the 12th scale in the case. It is an extension of Station 11 but has the additional challenge that the cylinder for scale 12 is not confined to the 11 elements of Station 11. In Station 11, relative densities are sufficient to rank the densities of the 11 elements. For the unknown element 12, the actual density is more elucidating. A calculator is provided so that visitors can divide the cylinder mass reading by the provided volume of the cylinder (3.22 cm3). Densities of the elements are shown in the posted periodic table along with a tabular list in the exhibit handout.30 Density results combined with tests for ferromagnetism, electrical conductivity, color, and luster should enable visitors to identify the element. Our Station 12 currently uses tin for the unknown, but zinc or cobalt could also conveniently and inexpensively be used.

Chemical and Nuclear Reactions

Problem-Solving Challenges

Station 16. A chemistry exhibit is expected to include chemical reactions, but this is where the constraints discussed in the first paragraph provide difficult obstacles, especially when cost, safety, and supervision are considered. To overcome this problem, two reversible reactions have been included in Stations 16 and 19. Neither the photochromic reaction in Station 16 nor the thermochromic reaction used in Station 19 consumes chemicals. For Station 16, commercially available UV beads and ornaments are mounted on a commercially available turntable37 that revolves once every 40 s (Figure 6). In addition the word “photochromism” has been painted with photochromic paint38 on a small card that is placed on the turntable. Suspended above the end of the turntable is a coiled black fluorescent light39 in a desk lamp holder. Every time the

Station 13. Station 13 uses a magnifying video camera interfaced with a computer to probe the microscopic world.36 One of the questions posed is “how does Velcro work?” The images clearly show the hooks and catches of Velcro. Other prepared microscope slides give visitors the opportunity to see insect body parts. In addition, visitors are able to inspect the tips of their fingers. Station 14. A magnetic stirrer without the word magnetic on the cover is provided for Station 14. Clamped on top of the stirrer unit is a sealed plastic bottle containing water with a few drops of food coloring and a stirring bar. Visitors are allowed to change the stirring rate and are excited by the creation of a whirlpool. The challenge is for the visitors to deduce the D

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Figure 5. Apparatus for the determination of electrical conductivities for Stations 11 and 12.

Figure 6. A motorized turntable rotates samples under the black lamp and by the Geiger counter for Stations 16 and 17.

photochromic materials pass under the light, their color darkens significantly but fades as the turntable continues around. This does represent a chemical reaction, as bonds are broken and formed upon the absorption of light. The process reverses shortly after UV light is no longer illuminating the photochromic material. Stations 17. The same turntable used in Station 16 is also simultaneously used to circulate several potentially radioactive materials for Station 17. At the opposite end of the turntable from the UV lamp is mounted a small Geiger counter.40 The objects in current use41 include a FiestaWare cup, a very old watch dial with radium on the hands, lantern mantles made by Coleman and Peerless, and a small sample of powdered uranium. The photochromic materials and the Coleman mantle do not set off the Geiger counter, but the remaining materials do cause considerable ticking. The discussion accompanying this station covers a very wide range from an explanation of isotopes and radioactivity to the science behind the Iran Nuclear Treaty. The counter can easily be interfaced with a computer for visual observation of radioactivity if desired.

make it clear that the science behind these two environmental threats is significantly different. Station 18 also includes models of penicillin G, amoxicillin and ampicillin (Figure 7). The replacement of a hydrogen in penicillin G with an NH2 group (not an easy process in the lab) to provide stability in stomach acid demonstrates a great example of drug design. Those visitors who have enough of a chemistry background to understand that ammonia is a base should be able to understand why the structural modification

Molecular Models

Station 18. Station 18 contains models of a variety of important relatively small molecules. Lewis structures and models of N2, O3, Cl2, CO2, H2O, NO2, NH3, CH4, C2H6O (ethanol), and C2H4O2 (acetic acid) are provided, and guests are asked to match each of the models with its Lewis structure. One of the reasons for including ozone and carbon dioxide is that some people confuse or do not distinguish between ozone depletion and climate change. The posted discussion tries to

Figure 7. Models of penicillin G, amoxicillin, and ampicillin are provided in Station 18. E

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Figure 8. Station 19 features a map on chromatography paper of the greater San Francisco Bay Area and the central valley of California with land threatened by sea level rise painted with green thermochromic paint. The image on the left shows the map without application of heat. The center image shows the map with a heat lamp on behind the image. The image on the right shows the map with substantial submerged land (now white) after about 10 s of exposure to the heat lamp.

would be submerged. Because the Bay Area scale is much bigger, it is much easier to see the changes for a sea level rise of 20 ft., which is within the realm of possibility in a few decades if action is not taken to phase out fossil fuels. The maps of the land mass remaining after the sea level rise are first painted and then copied on a duplicating machine onto chromatography paper. Then the additional land mass to reach present day sea levels is painted. This procedure minimizes the color difference between the land that stays with the sea level rise and the land that is submerged. When the maps are illuminated with a 250 W heat lamp,46 within several seconds the threatened land turns white. After the light is removed, the process reverses again in several seconds (Figure 8). Currently the light is used behind the map, although it works from the front as well. A hand-operated momentary switch is used by the visitor to turn on the light.47 Station 20. Station 20 includes four thermal maps available on the Internet that provide further evidence of global warming.48 To increase interest, an inexpensive IR camera49 that interfaces with smartphones and iPads was purchased. It has been set up so that visitors can take selfie thermal images and e-mail the photos to their home e-mail addresses (Figure 9).

was attempted and achieved success. It should be pointed out that the structural change might have changed or eliminated the antibiotic properties. Fortunately, experimentation demonstrated that amoxicillin and ampicillin are better antibiotics than the penicillin G serendipitously discovered by Alexander Fleming in 1928. As a side note, it took the urgency of the multitude of infections that resulted from wounds in World War II to stimulate the development of methods for the delivery of penicillin G. Climate Change and Thermal Images

Station 19. Scientists have the very important and serious responsibility of educating the public about the threats posed by human combustion of fossil fuels. After a brief mention in Station 18, Stations 19 and 20 follow up by presenting evidence far beyond a reasonable doubt that fossil fuels pose a significant threat to our environment and the quality of life. Most people have an opinion about how high society should rank climate change on a priority list. However, most also have an inadequate knowledge of the science of climate change and cannot name the three most abundant gases in dry air. Worse, many do not name nitrogen as the major constituent of air.42 Without knowing the composition of air, it is difficult to justify a naysayer approach to climate change. When it is understood that the percentage of carbon dioxide in the atmosphere is only 0.04%, it is a little easier to understand how human activity has changed the CO2 percentage. Understanding why this leads to global warming does require more education. Station 19 contains a question about atmospheric composition. Because many people will not take the time to read the posters with the scientific evidence for climate change, two interactive features have been included to capture the attention of visitors. A commercially available coffee cup has a world map on its outside. When very hot water is added, considerable coastal land disappears as a result of the use of a thermochromic material in the map.43 Because the changes are somewhat difficult to observe and the use of hot water in our exhibit would not be practical or safe, maps of the San Francisco Bay Area and Florida were painted with green thermochromic paint44 on chromatography paper. The maps were derived from a web site45 that provides maps of some regions as a function of the number of meters of sea level rise. For this exhibit, maps of the San Francisco Bay Area for 20 ft. and 100 ft. of rise and of Florida for 100 ft. of rise were made. A sea level rise of 100 ft. is probably a worst-case scenario, but the value was selected to make it very easy to see the land mass that

Visitor Feedback

Station 21. Station 21 is a suggestion box. At this point only preliminary observations about visitor experiences and suggestions can be made, as Exploring Matter was not officially installed in the Great Valley Museum until October 2016.

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OBSERVATIONS AND CONCLUSIONS The exhibit has received significant interest from K−12 students, college students, and the community. Exploring Matter has been utilized by multiple Modesto Junior College chemistry courses as a course project, exam, or extra-credit assignment. The following stations have received the most attention: 20, thermal imaging (general guests); 19, sea level rise as a result of fossil fuel use (general guests); 17, nuclear stability and radioactivity (college students/chemistry courses); 16, chemical reactions (general guests); 11 and 12, element identification challenge (college students/chemistry courses); 2, 13, and 14, drinking bird, microscopic vision, and magnetic stirrer (K−6 students). Some maintenance issues have been identified. Three low-cost drinking birds (Station 2) have had to be replaced because of inappropriate handling by guests. Small low-cost, hands-on items, including the magnets (Station F

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Steven Murov: 0000-0002-1282-5347 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS All materials used in this exhibit were purchased with funds from the American Chemical Society’s Collaborative Opportunities Grant and a Modesto Junior College Foundation Grant. The authors thank Great Valley Museum technician Samuel Leatherman, Enochs High School science instructor Dave Menshew, Enochs High School science students, and Carolyn Murov and Yamilette Villadolid of the El Concilio organization for suggestions and contributions to the display. The original mixed-media painting shown in Figure 1, was donated to the Great Valley Museum by Carolyn Murov.

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REFERENCES

(1) The central science. https://en.wikipedia.org/wiki/The_central_ science (accessed August 2017). (2) Jarman, R. Chemistry in the Museum. Featured in Education in Chemistry, Nov 6, 2015. https://eic.rsc.org/section/feature/chemistryin-the-museum/2000072.article (accessed August 2017). (3) (a) Ucko, D. A.; Schreiner, R.; Shakhashiri. An exhibition on everyday chemistry: Communicating chemistry to the public. J. Chem. Educ. 1986, 63 (12), 1081−1086. (b) Zare, R. N. Where’s the Chemistry in Science Museums? J. Chem. Educ. 1996, 73 (9), A198. (c) Allison, C. CatalystThe Museum of the Chemical Industry. Chem. Int. 2002, 24, 4−5. (d) Silberman, R. G.; Trautmann, C.; Merkel, S. M. Chemistry at a Science Museum. J. Chem. Educ. 2004, 81 (1), 51−53. (e) Domenici, V. The Role of Chemistry Museums in Chemical Education for Students and the General Public. A Case Study from Italy. J. Chem. Educ. 2008, 85 (10), 1365−1367. (f) National Academy of Sciences. Chemistry in Primetime and Online: Communicating Chemistry in Informal Environments: Workshop Summary. http://www.ncbi.nlm.nih.gov/books/ NBK91477/ (accessed August 2017). (g) Lowe, D. What Would Go Into the Chemistry Museum Displays, Anyway? http://blogs. sciencemag.org/pipeline/archives/2013/02/18/what_would_go_ into_the_chemistry_museum_displays_anyway (accessed August 2017). (h) Brown, M. K.; Brown, L. C.; Jepson-Innes, K.; Lindeau, M.; Stone, J. Bringing Organic Chemistry to the Public: Structure and Scent in a Science Museum. J. Chem. Educ. 2017, 94 (2), 251−255. (4) American Chemical Society. Collaborative Opportunities Grants. https://www.acs.org/content/acs/en/funding-and-awards/grants/ collaborative-opportunities-grants.html (accessed August 2017). (5) Modesto Junior College Foundation. http://www.mjcfoundation. com/ (accessed August 2017). (6) Murov, S. Exploring Matter: An Interactive, Inexpensive Chemistry Exhibit for Museums. Table of Contents. http://murov. info/EM-TOC.htm (accessed August 2017). (7) Murov, S. Liquid−Solid Density: Observations and Demonstrations. J. Chem. Educ. 2013, 90 (11), 1484−1485. (8) Drinking birds are available from many science supply sources, such as Educational Innovations. (9) For example, see: Rohrig, B. The Amazing Drinking Bird. http:// highschoolenergy.acs.org/content/hsef/en/what-is-energy/drinkingbird.html (accessed August 2017). (10) Educational Innovations. Touch and See Square. https://www. teachersource.com/product/touch-and-see-square/chemistry (accessed August 2017).

Figure 9. Thermal (infrared) picture showing three exhibit visitors and a snake using a FLIR One camera.

5), ball bearing and rubber stopper (Station 7), pennies (Station 8), and models (Station 18), have regularly disappeared. The chromatography experiment (Station 6) has rarely been made available because of our limited staffing/ volunteers. The sodas used at Station 10 last roughly 1−2 months before they start to leak and need to be replaced. The thermal camera and iPad (Station 20) have been moved to the front desk of the museum because of limitations of the batteries and charging issues. One reviewer made the excellent and appropriate suggestion that toxicity should be incorporated into Station 5. As a result, a toxicity chart has been prepared and posted by Station 5.16 It would be even better to have a sealed case with samples to give visitors a sense of the relative toxic doses of substances such as strychnine, potassium cyanide, methanol, nicotine, caffeine, Vitamins A, C, and D, warfarin, dioxin, aspirin, and glucose. For visitors wanting to explore matter further, the Great Valley Museum features an interactive Theodore Gray periodic table that contains samples of most of the elements.50 Museum gift shops might want to consider stocking several exhibitrelated items, including drinking birds8 (Station 2), magnetic kits13,14 (Station 5), and chemistry coloring books51 (Station 18), and perhaps even more expensive items such as the magnifying video camera36 or a less expensive model52 (Station 13). Hopefully, installation of chemistry exhibits into science museums will stimulate an improvement in societal science literacy. The Exploring Matter chemistry exhibit is especially intended to increase public understanding of the importance of chemistry and interest in learning chemistry. G

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(11) WS-001-3S Digital Weather Forecast Station Thermometer Barometer with 3 Sensors. (12) Enter “bismuth crystal” in the search function of sources such as Amazon or eBay. (13) Scientifics Direct. Search Results for: iron filings. https://www. scientificsonline.com/search_results?search=iron+filings# (accessed August 2017). (14) Educational Innovations. Sealed Iron Filings. https://www. teachersource.com/product/sealed-iron-filings/electricity-magnetism (accessed August 2017). (15) Scientifics Direct. The Mysterious Magnet Tube. https://www. scientificsonline.com/media/3052976_1.1000x1000.jpg (accessed August 2017). (16) Murov, S. Station 5A. Toxicities of Substances. http://murov. info/EM-st5A.pdf (accessed August 2017). (17) Sargent Welch. Chromatography Paper. https://sargentwelch. com/store/catalog/product.jsp?product_id=8869823 (accessed August 2017). (18) Murov, S.; Stedjee, B. Experiments and Exercises in Basic Chemistry, 7th ed.; Wiley: Hoboken, NJ, 2008; p 31. (19) Wikipedia. Penny (United States coin). https://en.wikipedia. org/wiki/Penny_(United_States_coin) (accessed August 2017). (20) Mauldin, R. F. Introducing Scientific Reasoning with the Penny Lab. J. Chem. Educ. 1997, 74 (8), 952−955. (21) Harris, T. How Liquid Motion Lamps Work. http://home. howstuffworks.com/lava-lamp.htm (accessed August 2017). (22) Educational Innovations. Flowing Color Spectrum (aka: Liquid Motion Bubbler). https://www.teachersource.com/product/flowingcolor-spectrum-aka-liquid-motion-bubbler/density (accessed August 2017). (23) Educational Innovations. Poly Density Kit. https://www. teachersource.com/product/poly-density-kit/density (accessed August 2017). (24) Kuntzleman, T. S. The Dynamic Density Bottle: A Make-andTake, Guided Inquiry Activity on Density. J. Chem. Educ. 2015, 92 (9), 1503−1506. (25) Will It Float? http://www.ddy.com/dl21.html (accessed August 2017). (26) Sanger, M. J. Whatever Floats (or Sinks) Your Can. J. Chem. Educ. 2006, 83 (11), 1632A. (27) Griffith, W. F.; Holley, K.; Mason, D.; Hogue, S. E.; Hunter, K. Discrepant Event: The Great Bowling Ball Float-Off. J. Chem. Educ. 2004, 81 (9), 1309. (28) eBay. 500g × 0.01g High Precision Digital Scale SF-400D2 Counting with USB Wall Adapter. http://www.ebay.com/itm/500g-x0-01g-High-Precision-Digital-Scale-SF-400D2-Counting-w-USB-WallAdapter-/381198858937?hash= item58c138fab9:g:yFcAAOxy3zNSiEoa (accessed August 2017). (29) Samples of elements were purchased from Metallium, Inc. http://www.elementsales.com/ (accessed August 2017). Prices for our selected elements averaged about $25 each. Many more than the 12 used at Stations 11 and 12 are available, but the prices for some elements are much higher. (30) Murov, S. Exploring Matter: An Interactive, Inexpensive Chemistry Exhibit for Museums. http://murov.info/visitorguide.pdf (accessed August 2017). (31) eBay. N50 Strong Round Ring Magnets 20mm × 4mm Hole 5mm Rare Earth Neodymium. For example: http://www.ebay.com/ sch/i.html?_odkw=neodymium+ring+magnets&_osacat=0&_from= R40&_trksid=p2045573.m570.l1312.R4.TR0.TRC0.A0.H1.X. TRS5&_nkw= N50+Strong+Round+Ring+Magnets+20mm+x+4mm+Hole+5mm+ Rare+Earth+Neodymium.&_sacat=0 (accessed August 2017). (32) For a downloadable video, please visit: http://murov.info/ station11video.MOV (accessed August 2017). (33) eBay. Metal electrodes Set of 12. For example: http://www. ebay.com/itm/Metal-Electrodes-Set-of-12-See-picture-anddescription-for-list-of-electrodes-/272128321572?hash= item3f5c1ca824:g:YDwAAOSwG-1WuRYt (accessed August 2017).

(34) eBay. 2P12T 2Pole 12Position 1 Deck Panel Wiring Band Channel Selector Rotary Switch. For example: http://www.ebay.com/ sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0. H0.TRS5&_nkw= 2P12T+2Pole+12Position+1+Deck+Panel+Wiring+Band+Channel+ Selector+Rotary+Switch&_sacat=0 (accessed August 2017). (35) For example: Improvement House. DROK®DC0-12V O-20Ω LED Digital Voltage Ohm Meter Electric Cigarette Atomizer Tester USB Rechargeable Resistance Volt Gauge Integrate Ohmmeter&Voltmeter Multimeter with USB Charging Cable for Vapes RDA. https:// improvement.house/DROK-DC0-12V-O-20-LED-Digital-VoltageOhm-Meter-Electric-Cigarette-Atomizer-Tester-USB-RechargeableResistance-Volt-Gauge-Integrate-Ohmmeter-Voltmeter-Multimeterwith-USB-Charging-Cable-for-Vapes-RDA/asin/B00S65R5WW (accessed August 2017). (36) Amazon. Crenova UM012C USB Digital Microscope 5MP Video Microscope 300X Magnifier Camera for Windows XP/VISTA /WIN7 /Mac OSX. https://www.amazon.com/Microscope-CrenovaDigital-Magnifier-UM012C/dp/B012G28SLC/ref=sr_1_8?ie= UTF8&qid=1483664120&sr=8-8&keywords= digital+microscope+camera (accessed August 2017). (37) Amazon. Leadleds 10 Inches Led Rotating Display Stand, Ideal for Phones Jewelry Model Souvenir Collectible Products and Photography (Black). https://www.amazon.com/dp/B00K763UIG/ ref=pd_lpo_sbs_dp_ss_1?pf_rd_p=1944687562&pf_rd_s=lpo-topstripe-1&pf_rd_t=201&pf_rd_i=B00JXGHGTA&pf_rd_m= ATVPDKIKX0DER&pf_rd_r=6CVX0RS83V5V0MAMFGZQ (accessed August 2017). (38) eBay. Photochromic Solar Pigment Sun Activated Color Changing Powder printing.https://www.ebay.com/sch/i.html?_ from=R40&_trksid=p2380057.m570.l1313.TR0.TRC0.H0.TRS1&_ nkw= Photochromic+Solar+Pigment+Sun+Activated+Color+Changing+ Powder+printing&_sacat=0 (accessed August 2017). (39) Wal Mart, Satco S7277 13W T2 Ultra Mini Specialty Spirals Screw-In Blacklight CFL bulb. https://www.walmart.com/ip/SatcoS7277-13W-T2-Ultra-Mini-Specialty-Spirals-Screw-In-Blacklight-CFLbulb/37682482 (accessed August 2017). (40) GQ Electronics. https://www.gqelectronicsllc.com/comersus/ store/comersus_dynamicIndex.asp (accessed August 2017). (41) Purchased from Amazon or eBay. (42) Murov, S. Climate Change: A Demonstration with a Teaching Moment. J. Chem. Educ. 2013, 90 (11), 1486−1487. (43) The Unemployed Philosophers Guild. Climate Change Mug. http://www.philosophersguild.com/Climate-Change-Mug.html (accessed August 2017). (44) eBay. 31°C Thermochromic Pigment Powders Mood Powder Changing Color Powder.https://www.ebay.com/sch/i.html?_from= R40&_trksid=p2047675.m570.l1313.TR0.TRC0.H0. X+31%C2%B0C+Thermochromic+Pigment+Powders+Mood+Pow der+Changing+Color+Powder.TRS2&_nkw= +31%C2%B0C+Thermochromic+Pigment+Powders+Mood+Pow der+Changing+Color+Powder&_sacat=0 (accessed August 2017). (45) Geology.com. Global Sea Level Rise Map. http://geology.com/ sea-level-rise/ (accessed August 2017). (46) Wal Mart, Satco S4999 - 250 W - R40 - IR Heat Lamp - Clear 5,000 Life Hours - 120 Volt. https://www.walmart.com/ip/SatcoS4999-250-Watt-R40-IR-Heat-Lamp-Clear-5-000-Life-Hours-120Volt/38271981 (accessed August 2017). (47) Harbor Freight, Momentary Power Foot Switch, Item#96619. https://www.harborfreight.com/momentary-power-foot-switch96619.html (accessed August 2017) . (48) NASA. GISS Surface Temperature Analysis. http://data.giss. nasa.gov/gistemp/maps/ (accessed August 2017). (49) FLIR ONE. Thermal Imaging Camera Attachment. http:// www.flir.com/flirone/ios-android/?pi_ad_id=102639511465&gclid= CjwKEAjwltC9BRDRvMfD2N66nlISJACq8591_ gBUzOSODyQZ8COYBu81vu_WY6_n-g8hNHBiX6bbSBoC5DDw_ wcB (accessed August 2017). H

DOI: 10.1021/acs.jchemed.6b01024 J. Chem. Educ. XXXX, XXX, XXX−XXX

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(50) The Most Beautiful Periodic Table Displays in the World. http://www.periodictable.co.uk/ (accessed August 2017). (51) Amazon. Chemistry Coloring Book. https://www.amazon.com/ s/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords= coloring+book+chemistry (accessed August 2017). (52) Amazon. Digital microscope camera. https://www.amazon. com/s/ref=a9_asi_1?rh= i%3Aaps%2Ck%3Adigital+microscope+camera= digital+microscope+camera=UTF8=1505241894 (accessed August 2017).

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DOI: 10.1021/acs.jchemed.6b01024 J. Chem. Educ. XXXX, XXX, XXX−XXX