Thursday, May 21, 2015

My Extra Credit Assignment: Turn a General Chemistry Topic into a Science Museum Exhibit

When traveling, I always make a point to explore local science museums. I look for engaging exhibits that explain scientific concepts in informative and fun ways. One such exhibit at the Science Museum of Minnesota asks participants to create carbon nanotubes using foam connectors. A few friends and I used our advanced degrees to produce the example shown below (sorry for the potato quality).

The exhibit engaged people of all ages in different ways. Just behind the exhibit you can see the little guy who, moments after the picture was taken, learned all about tearing carbon nanotubes apart while deploying a rather impressive Godzilla impression.

Nanotube

Since becoming a teacher I have a new appreciation for science museum exhibits. They are a literal manifestation of Einstein’s philosophy: “If you can’t explain it to a six year old, you don’t understand it yourself.” The best exhibits make the explanation entertaining too.

So, towards the end of this spring semester when my general chemistry students requested an extra credit assignment, I knew exactly what to assign. I asked them to take one of the concepts they learned in general chemistry and create a science museum exhibit to explain it.

The assignment allowed unlimited space and budget. I was less concerned about reality and much more interested in seeing their knowledge and creativity. In the end I was blown away by their creations and would like to share a few.

Dipole-dipole Board-

Dipole-dipole

The above exhibit, created by Taylor Trammell, showcases intermolecular dipole-dipole interactions. Her display contains many magnets–representing molecules–with two opposing sides, one positively charged (north pole) and one negatively charged (south pole). All of the magnets/molecules are free to rotate, except for one. Museum visitors can press a button and control the orientation of that one ‘molecule’. As it’s orientation changes, the other ‘molecules’ will reorientation to maximize dipole-dipole interactions and minimize the energy within the solvent.

A visitor could also walk up to the board with a strong bar magnet and introduce only it’s north or south pole of the magnet-filled board. That would represent the solvation of cations or anions through ion-dipole interactions. Taylor may not know it, but she found a fun way to introduce the solvent reorganization associated with Marcus Electron Transfer Theory.

Collision Theory Booth-

According to the Collision Theory of Reactivity, for a chemical reaction to occur the molecules must: 1) collide, 2) have enough energy to make and break bonds, and 3) have the correct orientation when they collide. Emily Nabong demonstrates these rules of engagement through a museum exhibit that repurposes an amusement park throwing booth. Instead of milk jugs or balloons, the target is a Velcro-covered molecule. And instead of baseballs or darts, visitors throw ‘molecules’ with different geometries and Velcro coverage at the target.

If the molecule is thrown with too little momentum or too little accuracy it will not hit the board (collide). Also, if the molecule hits the board with the wrong Velcro alignment it won’t ‘stick’ (correct orientation). The ‘reaction’ will only occur if the molecule is thrown hard enough and with the right orientation.

Collision

Amorphous vs Crystalline Solids

Miranda Ave introduced an interactive “build your own solid” exhibit that demonstrates the difference between amorphous and crystalline solids. It’s comprised of two building stations. The first station offers Magnetix (below left), which have curved connectors representing bonds and metal spheres representing atoms. The second station offers Tinker Toys (below right) with only one rod length (bonds) and wood circles that connect at 90° positions (atoms).

Solids

Any structure built with the Magnetix will lack long-range order like in an amorphous solid. In contrast, a structure built with the restricted connectivity of the Tinker Toys will have a continuous, repeating pattern like those observed in crystalline solids.

Tearing apart these structures will also help demonstrate differences between amorphous and crystalline solids. Tinker Toys break apart in a ridged manner along cleavage lines while Magnetix structures break in random places.

The building station will also be accompanied by a display with both crystalline and amorphous solids as well as an atomic picture of their structures.

Viscosity Race

Both Gabby Vega (below left) and Erum Kidwai (below right) proposed races between liquids to demonstrate differences in viscosity. They envisioned racetracks with several lanes, each labeled with a molecular structure. Museum goers would pick their ‘horse’ or lane and then watch as liquids ‘race’ down the track. Afterwards, each solution would be unveiled and the intermolecular forces dictating the viscosity and flow rates of the liquids would be explained.

Viscosity

Boyle, Lussac and Avogadro -

Jessica Metzger’s museum exhibit set out to teach people about the relationship between temperature, volume, number of moles of a gas, and pressure. She proposed three different interactive stations. The first (left) contains a cylinder connected to a pressure gauge with a plunger that can be pushed or pulled. When the plunger is pushed (or pulled) and the pressure increases (or decreases), the reading on the pressure gauge will increase (or decrease) just as predicted by Boyle’s law.

The second cylinder (middle) is completely enclosed and placed on top of a heating element. When the visitors press the button a red light will turn on indicating that the chamber is being heated. As the temperature increases, the pressure will increase in accordance with Lussac’s law.

The third cylinder (right) will be taller than the other two with a lid that can move up or down without allowing gas molecules to escape. The station will be equipped with a button that, when pushed, releases compressed air into the cylinder. So, when the button is pressed, the metal lid will move up and increase the cylinder’s volume to accommodate the newly introduced gas molecules (Avogadro’s Law).

PV = nRT

Electronegativity and polarity -

Carolin Hoeflich proposed an exhibit to introduce the concept of electronegativity and polarity. The exhibit includes a table with a soft foam cover and blocks representing the elements. The blocks are weighted so that electronegative elements are heavier. Museum-goers can arrange the blocks into molecular structures before dumping marbles–representing electrons–onto the table’s surface. The heavier elements will sink deeper into the foam and therefore ‘attract’ a larger number of marbles. When stepping back and looking at the structure as a whole, museum-goers will see that more marbles = more electronegativity. It’s also a fun way to visualize the dipole moment of a structure.

Electronegativity

Osmosis touch screen-

Hunter Hamilton introduced a touch screen exhibit to demonstrate the principles of osmosis and osmotic pressure. Visitors will use the screen to create an environment with more or less ions (red spheres) and one of three possible ‘membrane’ options: 1) no membrane, 2) permeable to water but not ions, and 3) permeable to water and ions. Once all selections are made, the visitors presses GO and observes which direction water and ions move in their environment.

Osmosis

Le Ch√Ętelier’s Principle-

Another touch screen exhibit, by Kelly Wyland, covers Le Ch√Ętelier’s Principle. Her screen displays an equilibrium with colors assigned to the reactants and products. It then asks users to predict the color change upon perturbation. After a prediction is made, the screen will show an animation that adds or removes reagents from the reaction mixture’s beaker. The color change of the solution will coincide with the concentration shifts to reach equilibrium.

LCP

Reaction Coordinate Slide -

I’ve saved the largest and most interactive exhibit for last. Nathan Horvat designed an exhibit with two slides that represent an exothermic and endothermic reaction coordinate diagrams. Children (maybe adults?) would start on the platform in the middle (as reactants) and climb one of two ladders representing the activation energy to the transition state before sliding down to the landing pads (products).

The ladder/slide to the left (or right) is for an endothermic (or exothermic) reaction because the end point is higher (or lower) in energy than the starting point. One thing that I found fun about this exhibit is that, while viewing it in action, you’d likely notice more children choosing the exothermic slide because the endothermic one requires more work for less return. In a statistical fashion, the children would find the product that’s more thermodynamically favorable.

rxn coord

 

 

 



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