Testing week

Home Chemistry experiments are on hiatus this week for state-mandated standardized testing for the kids (and so Mom can catch up on writing deadlines). Posts will resume soon! In the meantime, a joke:

Q: Why are chemists great at solving problems?
A: They have all the solutions.

More chemistry jokes (and explanations) here.

Paper Mache and Gluten

Mixed up some flour paste for a paper mache project I'm going to be working on this week. According to The Papier Mache Resource, it's the gluten in the flour that makes it sticky. The Exploratorium has an animation that shows how the protein molecules line up to form a gooey elastic mess. My batch developed a sticky skin that I skimmed off -- hopefully the remaining liquid is goopy enough!

Description of image, borrowed from ChemConnections:

Molecular model of the spiral structure formed by the HMW subunits of glutenin.

Endothermic Reactions

As a continuation of our foray into heat-producing (exothermic) chemistry, we mixed up some solutions that became colder (endothermic). Endothermic reactions involve electrons jumping to higher orbitals, which requires an input of energy. The atoms absorb energy in the form of heat from the surrounding environment, thereby lowering the temperature. Unfortunately notetaking that day was not optimal, but here is an idea of what we did:

Since we didn't have the recommended styrofoam cups for mixing our solutions -- which I assume were supposed to provide some insulation between the solution and the air temperature around it -- we used doubled-up paper coffee cups (just like my favorite coffee shop). We used a meat thermometer I found around the house (purchased for a greenhouse gas experiment I never got around to doing) and a 99 cent house thermometer I picked up at Wal-Mart. All the experiments dropped a few degrees almost immediately, going from a water temperature of about 60 degrees Fahrenheit (sorry, we're working in an American kitchen, not a lab with metric measurements) to about 55 or 50 in a minute or so. You could just barely feel the difference by putting your finger in it (we totally forgot gloves and eye protection for this one), so the thermometer is a must.


First was potassium chloride, found in salt substitute. We mixed in an unmeasured proportion with tap water.


Next, we cut open a cold pack from an old first-aid kit. The cold-pack consisted of two compartments, one containing urea (or crystalized peepee, used in cigarettes, pretzels, bath oils, cloud seeding, and tooth whitening -- although I think they make it artificially!) and the other water. You're supposed to squeeze the water portion, which I guess forces it into the other portion. We just poured the crystals into a cup and added water.


The third mixture was baking soda and citric acid. We only had a small jar (scavenged from some old science kit, I believe) so we put about half a teaspoon in the cup and mixed with a little water. Then we poured in some baking soda. It fizzed up nicely, of course, as it would with vinegar. According to about.com, the reaction was:
H₃C₆H₅O₇(aq) + 3 NaHCO₃(s) --> 3 CO₂(g) + 3 H₂O(l) + NaC₆H₅O₇(aq)


Finally, we mixed some calcium chloride -- the kind of road salt used to melt icy sidewalks -- with water. Surprise! This one turned out to be exothermic. The temperature went up to 78 degrees. Pretty neat.

Your name in elements

Theodore Gray, creator of the lovely Periodic Table Table, emailed me today with news of his element banners. The idea is to spell words or phrases using only the one- or two-letter element abbreviations, then illustrate the spelling with photos from the poster of his table. The banners are pricey, but you can have fun just seeing how your name looks in elements. See a different version of my name here.

Crossposted to GeekDad.

Elementeo

Elementeo is a strategic battle game where you use your elements across the battlefield in reducing opponent’s electrons to zero. You do that by harnessing the strength and moving properties of the elements and compounds, and by using their reactionary powers. For example, Oxygen can rust any neighboring metal or Copper Conductor can shock any metals and send them back to the deck. According to the game's inventor, Anshul Samar, an eighth grader:

Each card has fantasy, education, and fun all mixed in. From the educational side, one card contains the atomic number, elements family, atomic mass, state at room temperature, oxidation state, and symbol of one element. Compound cards include formulas and how dangerous or flammable the compound is in our world. Alchemy cards go over a wide range of chemistry and physics subjects.

The game should be available the end of this month at the Elementeo website.

Thanks to my friends at Geekdad!

Nitric Acid and Ethanol

Tonight we saw an episode of "The Simpsons" where Bart lets loose a python in the school chemistry lab. A flask full of ethanol is knocked over, followed by a flask full of nitric acid (labeled "Do Not Mix with Ethanol"). The combination forms a toxic gas.

The Simpsons is known for sprinkling math and science references throughout its scripts. (See Paul Halpern's book, right.) That's because many of the show's writers have advanced degrees in the subjects, including writer Bill Odenkirk, who has a Ph.D. in chemistry and George Meyers, who holds a degree in biochemistry from Harvard. In this episode, first aired last May, a math textbook gets shot and "bleeds" equations, and physicist Stephen Hawking makes an appearance in a flying wheelchair.

However, it turns out that the writers got this one wrong, as noted in this entry on tv.com:

When nitric acid & ethanol are mixed in this episode it produces a toxic gas. In fact, mixing these two chemicals will make a very explosive mixture, not a toxic gas.

Or if you don't care to rely on chemistry facts from a TV website, here's a more reputable source.

Aspirin Lab

Lesson: Acid-catalyzed hydrolysis of acetylsalicylic acid to salicylic acid and acetic acid
What Happened: We dissolved the active ingredient of aspirin in water, separated it from the binder, then purified the drug using sulfuric acid as a catalyst.

The World of Chemistry video series, which you can watch online at Annenberg Media, has been serving as our spine lately. We were up to the episode on catalysts this week, so I found a demonstration from The Joy of Chemistry (actually from the chapter on organic chemistry) which used dilute sulfuric acid (sold as aquarium pH lowering solution) as a catalyst to purify aspirin. FYI, another example of a catalyst at work were the pineapple enzymes we used to dissolve Jello.

According to Wikipedia, the end product of this demonstration, salicylic acid, is what aspirin metabolizes into in the liver. Its name comes from the Latin word for the willow tree, Salix, from whose bark it can be obtained. Interestingly, it can also be derived from methyl salicylate (oil of wintergreen). In 1897, Felix Hoffmann, a chemist at Friedrich Bayer & Co., obtained acetylsalicylic acid by a reaction of salicylic acid and acetic anhydride; this is the basis for Bayer's claims to the discovery of aspirin.

Materials:

Safety glasses
Rubber gloves
10-15 aspirin (plain or buffered)
½ cup (120 ml) rubbing alcohol (70% isopropyl)
2-4 large glass containers (we used a Pyrex bowl and old honey jars and canning jars)
Coffee filters and rubber bands
Sturdy plastic spoon
Aquarium lowering solution (dilute sulfuric acid)
Pipette or straw

1. Place aspirin in glass.
2. Pour in alcohol, a little more than needed to cover the aspirin.
3. Heat the glass in the microwave on 50% power for 30 seconds until warm but not boiling. The acetylsalicyclic acid will dissolve in the alcohol, leaving the starch binder.
4. Gently crush remaining residue with spoon to extract as much acid as possible. Let sit 15-30 minutes.

5. Take coffee filter and spread it over top of second glass. Push it down slightly so it resembles a funnel. Secure with rubber band.
   
6. Carefully pour the solution through the filter. The liquid that drips through is called the “mother liquor.” The acetylsalicylic acid has dissolved in the water. What's left on the filter is the starch binder that holds the drug in the pill shape.
   

7. Wearing gloves, dispose of coffee filter. Don’t touch the wet part.
8. Run a small stream of cold tap water. Take the glass with the mother liquor and add water until it is about ¾ full. Small white flakes of acid should begin falling out of solution. Let sit for a couple hours.
   

9. Set up another filter on another glass. Pour mixture through filter to separate out the crystals. Filter 2-3 times if needed, letting solution sit for 1-2 hours in between.
   
10. Allow to dry overnight, away from breezes. The crystals will become fluffy.
11. Take ¼ of wet or dry crystals and put into glass. Add aquarium solution dropwise with a pipette or straw until the entire sample is completely covered. The sulfuric acid is the catalyst and remains at the end, so be careful with the liquid.
12. Heat the mixture in the microwave for no more than 15 seconds at 50% power. It may start to steam immediately.
    
13. Remove glass. You should smell vinegar (acetic acid) evaporating. If not, wave your hand over the glass to waft the fumes towards your nose. The sludge that remains is salicylic acid.
14. Dispose of solids in the trash and liquids in the toilet.
    

NOTES: We ended up doing the demonstration twice -- although, as it turned out, we probably didn't need to -- because the shopping list at the beginning of the book didn't specify that the alcohol needed was 70% concentration. I found an old bottle of the right concentration, and we did everything over. However, we discovered that letting the first solution sit and filtering it several more times yielded enough crystals to do the demonstration.

In the end, we had twice as much acetylsalicylic acid as we needed. We probably used too much in the final step (as well as too much sulfuric acid, which I tried to pour slowly out of the bottle instead of using a pipette) because when we put it in the microwave, it immediately started steaming! I turned it off a few seconds short of 15 and the vinegar smell was overwhelming.

April Fool's!

The Periodic Table of Rejected Elements -- containing such families as the Dingy Gases of L (Linoleum) and Vi (Visine) -- was created by Michael Gerber and Jonathan Schwarz for the Atlantic Monthly.

Here's another cute variation: The Periodic Table of Hardware.

B is for Bolt, Al is for Aligator Clip, Kr is for Key Ring. From artist Jim Rosenau's site This into That.

I did a search for any other chemistry-related April Fools items, but all I could find were teachers who informed their class there would be a major quiz. Since I don't do grades, I'll give you a pass on that one!