Lensyl Urbano – Page 194 – Montessori Muddle

Atomic mass versus atomic weight

Isotopes of hydrogen: hydrogen, duterium and tritium.

I have been told by reliable sources that the difference between atomic mass and atomic weight is that the atomic mass is the mass of a single atom (number of protons plus the number of neutrons), while the atomic weight is the averaged masses of all the different isotopes you would find in a natural sample.

This obviously requires a discussion of isotopes, which may be a topic best left for high school. However there are a number of interesting hooks that could capture the imagination.

One of them is the use of isotopes to trace sources of your diet. Isotopes can tell how much meat a person eats (nitrogen-15) or how much of the carbon in their body comes, ultimately, from corn.

Corn, chemistry and the food you eat

Corn_tassels
It’s absolutely amazing how much the different numbers of neutrons in atoms can tell us about the ourselves and the world. Over 99% of the carbon in the atmosphere is carbon-12, with 6 neutrons and 6 protons, but the rest is made of carbon-12 (6 protons and 7 neutrons) or carbon-14 (6 protons and 8 neutrons).

Carbon-14 is radioactive and is used to date things for archeology and climate change etc. However, when it comes to our diet carbon-13 is a bit more interesting. Some plants, particularly grasses like corn, do photosynthesis a little differently so that they tend to have more of the slightly heavier carbon-13 isotope than the others. As a result, if you take a blood sample, you can tell (roughly) how much of your diet ultimately came from grasses.

Why is this interesting? Because when you eat meat, there is a good chance that the animal you are eating was fed with corn. If you look at the pre-packaged items in the supermarket, you’ll find that high-fructose corn syrup is an important ingredient on many of them.
The documentary King Corn, and the book The Omnivore’s Dilemma find that if you trace the modern industrial food chain much of it starts in the corn fields of the mid-west. We eat, in one way or another, a lot of corn. In fact, blood samples have found over 50% of the carbon in our bodies comes from corn and similar grasses (like sugar cane).

This article describes a number of other interesting applications of isotopes in investigating diet. A more technical description of carbon-13 and diet can be found here.

Choose your own adventure on a Wiki

I was listening to an On The Media interview of Bob Stein on the future of books and started to think about how to use collaborative writing in my class. Since we use our wiki allot (for practically everything), it occurred to me that the wiki is the ideal platform for students to write a choose-your-own-adventure type story. A quick web search there is already a choose your own adventure website/wiki that is set up just for this.

The way I envision it working in my class is that each student would write a section/chapter and end with a set of choices which would be links to new chapters. To make it interesting and more collaborative, very time students had to add to the story they would have to start from another student’s decision.

I really can’t wait to try this. I think I’ll make a new section of the story a weekly writing assignment.

Asynchronous lessons

Halite — 3D model of halite unit cell from GeoMod

An interesting thing happened last week that I perhaps should have anticipated. Because we had a little extra time during Thanksgiving week I offered to do a technology lesson on 3d programming if anyone was interested. One student was very interested and a couple others wanted to do it later. I usually try to do basic lessons for everyone at the same time in order to save time, but because the one students was very excited about the lesson I just gave it to them.

Over the next two days, the first student had given the lesson to another who’d planned to wait until later, and I was having requests from other students who had not been interested in programming at all to be able to do the subject.

I guess I learned a couple things from this. First, that asynchronous lessons might be something I should do more often. If certain students are more interested in the subject then the lesson is more effective given to them. Second, that student interest in infectious. If they are excited about a subject they tend to want to share with others, and that seems like a very effective way of propagating information; each student only gets the info when their interest has been sparked. Furthermore, since different students are more interested in different subjects they, theoretically, all have the opportunity to be the expert, if they’re interested in that type of recognition. The trick, I guess, is making sure that everyone gets the lesson and information at some point before they loose interest.

Apprentice sentences: Sarah Palin?

Slate has a great apprentice sentence contest called can you write like Sarah Palin. The Slate post dissects Palin’s sentences beautifully as having: “multiple references to local flora and fauna, heavy use of PSAT vocabulary, slightly defensive tone, difficult-to-parse meaning”. One example sentence, “As the soles of my shoes hit the soft ground, I pushed past the tall cottonwood trees in a euphoric cadence, and meandered through willow branches that the moose munched on.”

Cat traps

One interesting metaphor for teacher-student interactions is that of cats and dogs. Cats tend to want things like acknowledgment and praise on their own terms. They can be quite the challenge to interact with and it is often difficult to get them to show interest in anything. One thing that’s worked for me is to leave “cat traps” around the classroom. The box of pulleys, or a couple boxes with batteries, wires and motors. The “traps” are usually related to something we’ll be covering later in the year, but they are left out with no explanation or instructions for purely exploratory experimentation. I might, if they seem interested, show them something cool that can be done with the gear once I see them start playing with them on their own.

By the time the subject comes around in the curriculum the cats have usually developed a pretty good basic idea of the gear and have often shared this with others. I think it is a great way of driving learning through intrinsic student interests and peer-teaching. The only problem, is sometimes the students will gravitate toward the traps more than toward what they’re supposed to be doing.