Middle and High School … from a Montessori Point of View
A while back, I posted a radio article by Planet Money on why gold is so valuable, and has been used for money for so long (God, Glory and GOLD: but why gold?). They’ve now created a nice video explaining the same thing. Though there’s less detail, the dramatic visuals (of the reactivity of sodium for example) make it quite interesting.
Back in the day, if you wanted a non-stick cooking skillet, your best option was to do it yourself by seasoning a cast metal pan. Sheryl Canter has an excellent post describing the science behind the “seasoning” process. The key is to bake on a little bit of oil to create a strong cross-linked polymer surface. This is a nice tie into our discussion of polymers and polymerization in the middle school science class; although I’m not sure how many of my students have actually seen a cast iron pan, or even know what cast iron is.
To season, you coat the pan with a thin layer of oil and bake it for a while (without anything in it). Baking releases free radicals from the metal that react with the oil to create a cross-linked polymer that’s really hard to break down or wear out, and prevent food from sticking to the pan. Different, cross linked polymers are used in car tires for their durability, but probably not for their lack of stickiness.
Apparently, linseed oil is the best seasoning agent, but it might be a bit hard to find.
Most non-stick, artificial surfaces, are also made of polymers of hydrocarbons, silicon oxides and other interesting chemicals.
In the lab, you can make your own cross-linked polymer “slime” by adding a solution of borax (sodium tetraborate) to a solution of polyvinyl alcohol (1:1 ratio of concentrations) (Practical Chemistry, 2008).
The result is a satisfying goo.
The middle school started science this week with a mysterious jar of unknown substances: a couple immiscible liquids; some plastics and metals of different densities.
As they try to separate and identify the mixture they’ll be learning about handling potentially hazardous materials, material physical and chemical properties (like density and pH), and a little chemistry.
But the first thing they need to learn is how to take notes. Science starts (and ends) with observation. Careful observation. And most middle schoolers need mentoring to make sure their notes are rigorous.
To this end, after they wrote up their observations of what was in the jar, I put together my own notes as a general reference. This is not the only way to take notes, but I’m going to have them amend their own notes to make sure they’re neater and have as much detail as possible.
Daniel Shechtman was just awarded the Nobel Prize in Chemistry (2011). He discovered that matter can exist not only as crystals, which have a regular geometric arrangement of atoms, and amorphous non-crystals that do not, but also as quasicrystals which have a different type of atomic ordering.
The Guardian has an interesting article on Schechtman, whose discovery was roundly disbelieved by other scientists and he was ridiculed for years.
In an interview this year with the Israeli newspaper, Haaretz, Shechtman said: “People just laughed at me.” He recalled how Linus Pauling, a colossus of science and a double Nobel laureate, mounted a frightening “crusade” against him. After telling Shechtman to go back and read a crystallography textbook, the head of his research group asked him to leave for “bringing disgrace” on the team. “I felt rejected,” Shachtman said.
— Sample (2011): Nobel Prize in Chemistry for dogged work on ‘impossible’ quasicrystals in The Guardian
Hat tip to M. Eisenberg for this link.
Want to find your nearest superfund site? The EPA has an interactive page called, Clean Up My Community, that maps brownfields, hazardous waste, and superfund sites anywhere in the U.S.
Note:
Molecular models tend to fascinate. As a introduction to the chemistry of elements, students seem to like putting them together, and they tend to enjoy finding out what their molecules are called.
You can’t beat fitting together molecules by hand as a learning experience, but 3Dchem has a nice collection of interactive, three-dimensional molecules, including molecules of the month.
They also have three-dimensional periodic tables showing the sizes of the atoms in the traditional tabular form as well as a spiral.
The objective is to show the shape of the whole and to express the beauty and cosmic reach of the periodic system.
— Stewart (2006): The Chemical Galaxy
The traditional periodic table of the elements breaks the elements into rows as their chemical and physical characteristics repeat themselves. But since the sequence of elements is really a continuous series that gradually increases in mass, a better way of displaying them might be as the spiral, sort of like the galaxy.
When the chemical elements are arranged in order of their atomic number, they form a continuous sequence, in which certain chemical characteristics come back periodically in a regular way. This is usually shown by chopping the sequence up into sections and arranging them as a rectangular table. The alternative is to wind the sequence round in a spiral. Because the periodic repeats come at longer and longer intervals, increasing numbers of elements have to be fitted on to its coils. …
The resulting pattern resembles a galaxy, and the likeness is the basis of my design. It seems appropriate, as the chemical elements are what galaxies are made of.
…
The ‘spokes’ of the ‘galaxy’ link together elements with similar chemical characteristics. They are curved in order to keep the inner elements reasonably close together while making room for the extra elements in the outer turns.
— Stewart (2006): The Chemical Galaxy
While the spiral version of the periodic table is not used a lot, it is scientifically valid. There are other ways of representing the spiral and the periodic table itself. It all depends on what you want to show.
Indeed, Mendeleev’s monument in Bratislava, Slovakia has the elements arranged as the spokes in a wheel.
So other than digging in Morocco, where do we get more phosphorus? Here’s a hint: the symbol for phosphorus on the periodic table… is “P.”
— Horwich (2011): The end of phosphorus on APM’s Marketplace.
Marketplace’s Jeff Horwich has an excellent article on the uses of the element phosphorus, where it comes from, why it’s getting scarce, and where we might get more.
The answers to these questions are:
Marketplace tells the story in much more detail.