entertainment

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 to 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 stations 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 Châtelier’s Principle

Another touch screen exhibit, by Kelly Wyland, covers Le Châtelier’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 coordIn closing, I want thank my students for a great semester and to share my appreciation for the students who designed these exhibits. It was a pleasure to teach them and to see them come up with such creative ideas. I hope one day, during a random science museum visit, I find one of these exhibits in action.

 

 

 

What if water had memory?

It spent some time in a homeopathSome homeopaths believe water has memory. That is how they explain the “medicinal properties” of their concoctions. Apparently people are treated even though the pill or potion may not contain a single molecule of the medicinal agent. But does water really have memory?

That depends on how you define memory. If for water it is defined as the property to have a stable state for sometime, then it has memory, just not a very good one – 50 femtoseconds is its retention time. That’s about 60 million million times shorter than the mythical goldfish’s three-second memory.

But with that “memory”, water could not retain any useful information. The memory is just its ability to form an ordered group of water molecules that can last for 50 femtoseconds. It is a bit like a crowd of people all milling around in train station – there are pockets of order where people are standing around looking at departure boards or getting a coffee. But these groups will disperse after a while. And so it is with water – there are pockets of order where the water molecules are interacting with each other and with things that are dissolved in it, but these are lost pretty quickly.

Let’s try another question. What if water had an elephant’s memory and never forgot?

In that case all the ordered pockets would hang around forever. But it wouldn’t look much like liquid water anymore. Instead it would be quite different; in fact, you would probably call it ice.

How about we try something a bit more bizarre? What if water could remember the molecules that had been dissolved in it long after the original molecules had been diluted away? And then what if that water could still act like them?

That may sound pretty outlandish, but a paper published, in the journal Nature (no less), suggested just that more than 25 years ago. Not surprisingly it proved rather controversial. Pretty soon after publication the paper was discredited, leaving no sound evidence for water being able to remember what has been in it (for any significant length of time).

But let’s ignore the evidence for a moment: what if water could retain a fond memory of long-departed solutes? In that case we’re in trouble, because, as one of my teachers used to say, “chemistry is the study of the soluble”. She meant that chemistry, mostly, involves dissolving compounds in solvents and then reacting them together to get new and interesting compounds. Water is a favourite solvent because more things dissolve in it than anything else.

However, if water can remember what had been in it then even in its purest form it would behave like it was chock full of impurities, with unpredictable results. No chemical reaction performed in water, from DNA fingerprinting to synthesis of a new drug, would ever work consistently.

But water memory isn’t just bad news for chemists – it would also affect the behaviour of your everyday tap water. One day your glass of water might have a flashback of limonene adding a pleasant hint of citrus fruit, the next it might recall capsaicin giving your water a spicy kick.

No need to worry, things wouldn’t get that far. After all you’re 70% water, life evolved in water and almost all reactions in all living things happen in water. If the primordial soup could have been influenced by non-existent chemicals then there would have been no stable environment for the life to have formed. Thus no life, no evolution and no human beings to dream up homeopathy.


Illustrations are by Martin Parker, chemistry teacher at Ampleforth College.

The Conversation

This article was originally published at The Conversation.
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By October 3, 2013 6 comments entertainment, fun

Twitter Brain’s Chemistry Novel (and other book) recommendations

I’ve been looking for an easy to read book (fiction or non-fiction) to send out to chemistry students before they arrive at Uni. The plan is to have all our first years read the same book before they arrive. With any luck it will give them something to chat about and give our first few lectures a point of reference.

So I asked the twitter brain for its chemistry book recommendations, and here’s what it came up with.

  1. @Sci_ents @DrRubidium Anyone say Greg Benford’s Timescape? More physics but includes NMR, time travel, eco-disaster, and academics.
  2. @Sci_ents @DrRubidium I can recommend an author… Peter Watts.. his first series is chock full of science goodness including chemistry
  3. @sci_ents we’re partial to this one: ht.ly/mrHGn Short stories about a deadly assassin who uses a different poison for each kill
  4. @ChemistryWorld @Sci_ents My friend told me to read “The Disappearing Spoon” by Sam Kean. I just checked it out from the library!
  5. @Sci_ents I enjoyed ‘The Girls of Atomic City.” It tells the story of the nuclear bomb development from the “blue collar” people working…
  6. @simonbayly @Sci_ents @ChemistryWorld It was Mr Levi whom inspired me onto the chemical trail at age 14. Highly recommended reading.
  7. @BytesizeScience @Sci_ents Goethe’s “Elective Affinities” is a Classical example, but highly metaphorical. Downhill from there.
  8. @Sci_ents @ChemistryWorld Mr Tompkins by George Gamow
  9. @Sci_ents @ChemistryWorld The Periodic Table by Primo Levi isn’t a novel exactly, but it is one of the best books ever.
  10. @Sci_ents @ChemistryWorld @Sci_ents not sure if this counts but “cat’s cradle” by Vonnegut has some nice ideas en.wikipedia.org/wiki/Ice-nine
  11. @Sci_ents Interesting physics and chemistry in Reflex by Dick Francis. Not exactly concepts though, more application.
  12. @Sci_ents @ChemistryWorld not really a novel but The Periodic Kingdom by P W Atkins is a great read
  13. @Sci_ents The Documents in the Case, Dorothy L. Sayers. Not much chemistry until the clincher which is chemical concept. (DM for spoiler)
  14. @Sci_ents When I was undergrad, one grad inorg cume at WUSTL included question, “Who killed Missy Moonbeam in The Delta Star?”
  15. @Sci_ents @ChemistryWorld
    Uncle Tungsten: Memories of a Chemical Boyhood by Oliver Sacks
  16. @Sci_ents @ChemistryWorld Susan Gaines’ Carbon Dreams?
  17. @Sci_ents @ChemistryWorld – Napoleon’s Buttons: How 17 Molecules Changed History, Penny Le Couteur
  18. @Sci_ents Not exactly fitting the criteria but Primo Levi’s Periodic Table comes to mind
  19. @Sci_ents Primo Levi’s The Periodic Table en.wikipedia.org/wiki/Primo_Levi some named as best science novel ever
  20. @Sci_ents @ChemistryWorld or cat’s cradle if gravity’s rainbow is too much of a slogger
  21. @Sci_ents Emm short answer no. Long shot- Dune. Spice as a drug, water harvesting and terraforming. Best I can do ad hoc
  22. @Sci_ents A Whiff of Death (I. Asimov) — murder mystery set in Chemistry department… The Delta Star (J. Wambaugh) — similar plot.
  23. @Sci_ents @ChemistryWorld gravity’s rainbow, imopolex g

 

Did we miss any?

#ChemMovieCarnival: Criminal Minds

Criminal Minds is one of my favorite television shows. It follows a team of FBI agents in the Behavioral Analysis Unit. They examine the psychology of crime scenes and the choices of the criminal before, during, and after a crime to build a behavioral profile which ultimately leads to the arrest of the criminal.

The show doesn’t lend itself to chemistry in every episode, but sometimes the show features some interesting opportunities for chemistry. I’ll highlight two here: one light and one sinister.

The resident nerdy genius, Dr. Spencer Reid, (someone to whom I have been compared an uncomfortable number of times…) displays some chemistry magic in a throwaway scene in a season two episode: “Profiler, Profiled.” He wows his coworkers with a ‘magic’ film canister (kids ask your parents what a film canister is) which explodes and shoots like a rocket across the office. Sadly, he calls this merely physics magic, but we’ll let it slide. While the magician doesn’t reveal his secret, it is almost certainly an Alka-Seltzer tablet in water. The bicarbonate and citric acid generate carbon dioxide, which builds up the pressure and causes the canister to fail. Very easy to try at home, where you could also use baking soda and vinegar.

The second example is much more nefarious. In a season six episode, “Sense Memory,” a criminal has an obsession with scents – bad news for a cab driver inundated with aromas every day. We see him flash back to his childhood and, probably, the scent of his mother. This turns criminal when several of his passengers go missing and end up dead. The team’s first clue is the large amount of methanol found in the victims’ lungs. Reid uses his nerdy genius again to educate the team on the properties of methanol.

I’m ok with most of what is presented here… it’s not too bad. Except when he claims methanol can be turned into plywood. Plywood is not made from methanol. In attempting to figure out just what they were talking about, I found that Criminal Minds’ script likely quotes almost directly from methanol’s Wikipedia page. The only latitude I’ll give them is that methanol is turned into formaldehyde which is converted to urea-formaldehyde, the resin used to hold sheets of wood veneer together to make plywood (all also found on Wikipedia).

But enough about that – that’s not even the most interesting chemistry in the episode. It’s the reason why the criminal needs methanol that’s interesting. It’s not just to murder his victims – while that would be unique, it would be perhaps a bit unnecessary. No, instead he needs the methanol in connection with his obsession with scents, particularly the scent from his childhood. His obsession leads him to attempt to preserve that scent, particularly when his job exposes him to so many unpredictable, and often offensive, odors.

He waits until he accepts a passenger with that critical aroma, then abducts them and drowns them in methanol. Essentially, he’s trying to capture eau de humaine. He soaks his victims in methanol to extract their essential oils. Then he distills the resulting solution to concentrate the oils, which he adds to homemade candles to preserve the scent. Some of the setup is questionable (why does the condenser not have water running through it?), but the concept is still interesting and correct enough for me.

Extraction, distillation, essential oils … very gross and disturbing, but creative fictional use of chemistry nonetheless. It goes without saying that you should not soak your friends in methanol for any reason (or your enemies). Instead, stick with chemistry and physics magic with Alka-Seltzer. Your friends will like you much better this way.

By April 21, 2013 2 comments chemical safety, entertainment, fun