The Craft of Teaching

teachingmeme1This meme appeared on a teachers’ Facebook group called TeacherGoals. Predictably, within 11 hours, it gained 900 likes among its 159 000 followers .

The saying is something I’ve heard often throughout my teaching career. Variation of approaches is at the disposal of every experienced teacher, who will use them successfully.  But as is the case with political views, it’s best not to feel smug or, worse, superior to someone else merely for adhering to a particular idea.

For instance, contrary to what is being promoted in this case, the same delivery could work the second time around if

(1) the lesson is delivered more slowly

(2) the teacher or student is not as tired

(3) if there are less distractions

(4) if the concept needs a period of incubation, which is often the case, and so on.

As usual memes oversimplify everything. They’re better at boosting Facebook’s revenues than at advancing pedagogy.

Here are a few guidelines and strategies that teaching colleges, certification boards and professional associations might find useful to better train science teachers. Some may seem obvious to the outsider, but you’d be surprised how seldom they are implemented. And, of course, our students get shortchanged.

(1) For high school math and science, a teacher should have at least a bachelor’s degree with a major in the main subject they teach. This not only increases the likelihood that the potential teacher’s basics have been reinforced, but it gives him an inkling of where a particular concept or skill can lead. Equally important, knowing that he is only scratching the surface of his subject, the teacher with a better background can be more convincing that the very basics are within anybody’s reach—as long as there’s a bit of an effort on the part of both the student and the teacher.

(2) Work experience related to the subject is more of an asset that some people realize. Working in three different analytical labs gave me a lot of practical skills that came in handy in managing labs and keeping better standards for my students. Ideally, occasional work terms should replace so-called “professional development”, which often amounts to little more than exposing teachers to sales pitches from educational industry representatives or to people promoting the latest flavour of the year in pedagogy.

(3) Student teachers do not have to be sent into the field for the very long periods that have unfortunately become customary. Given that most student teachers are not as effective as most experienced teachers, a large chunk of the high school student’s course is compromised. As an alternative, student teachers can prepare several lessons and lab activities for other student teachers while being filmed. Peers along with the supervisor and student teacher can then view the films and give constructive criticism.

(4) The most common role model for human beings is the electron because most people choose the path of least resistance. If, by setting an example, a teacher can prevent at least some of his students from imitating the negatively charged constituent of matter, he will have taught them one of life’s most valuable lessons.

 

 

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Thirteen (mostly) Chemistry Demonstrations in 280 Characters Or Less

  1. Ground #helium balloons with a bunch of grapes. Then remove 1 grape at a time until the buoyant & gravitational forces balance out. The balloons will be suspended in the air. Children quickly catch on and have injected a little #science into an otherwise dull wedding reception.
  2. Add copper to HCl & watch nothing happen. Add Cu to HNO3, & NO2 or NO forms, depending on the acid’s concentration. Add CuO to citric acid, wait a few days & a (patina-like?) material forms.
  3. ZNO44To a beaker, add sand and a 50% solution of methanol. Then add spatula tips of zinc oxide powder. Close lights. Transitions are very temperature-dependent and different parts of the flame create a variety of colors. Students prefer demo to drugs.
  4. Add calcium to water & phenolphthalein. Collect H2. Ignite it. Color change in solution reveals hydroxide formation. White precipitate of CaO settles below fuchsia solution. Filter it. Blow into solution of Ca(OH)2 to form CaCO3. More CO2 forms acid, gets rids of cloudiness.
  5. ammoniaAdd 2 drops of bromothymol blue to a (pH ~ 4) solution in a flat-bottomed flask. Add dilute NaOH to beaker. Bring the flask to a boil for 3-5 minutes. Remove heat source & wrap a cold, wet rag around the flask. Be awed by work of ΔPV.
  6. Get a hand-held digital microscope. Use it to reveal  the sensuous surface of a grapefruit, an aborted seed; and the oxidation of copper in an old penny. 

SANYO DIGITAL CAMERAChip off 5 samples from a boulder. Use water displacement in large cylinder to find the volume of each piece. Mass each rock. Obtain average density. With latter & an estimate of the boulder’s volume, get an estimate of the boulder’s mass.
8. Get a thin flow from a water tap. Wrap cotton shirt around a plastic comb. Rub it. Move the comb towards the water without touching it. Watch the stream bend like a banana. Water is neutral, but something charged within it is attracted to the oppositely charged comb.Static 9. Demonstrate that old pieces of magnesium often won’t flash in a Bunsen burner flame. Their surface has reacted with air. Wipe a piece with a paper towel that’s wet with dilute acid. Dry, weigh, ignite& look away! After it flashes, reveal that white residue’s mass > than original.
10. CO2Add two drops of bromothymol blue to 4 different test tubes containing tap water. Add distilled water to the 1st; it remains green. Add baking soda to 2nd, get blue. To the 3rd and 4th add vinegar & dry ice (CO2). Both go yellow as both additives lead to H+.

11. Ignite a hydrogen-filled balloon. Note red color from excess H2 incandescing in heat of reaction. Fill a 2nd balloon with 2:1 ratio of H2 to O2 & ignite; observe no red color. Fill 3rd balloon with hydrogen and add a little copper sulfate. Explosion becomes green-colored.

12. Spread a few grams of iron filings on a filter paper. Place it a magnetic stirrer. Turn it on at medium speed. A beautiful display of a magnetic field in motion ensues. It resembles a living colony of microorganisms.

13. The calcium carbonate in blackboard chalk is long-baked, so it quickly settles, and more stays out of the respiratory system. Yet, if you examine any ledge or border high above the board, it fills with chalk dust over the school year. How? Brownian motion.

14. Imagine someone you has wronged you. Imagine taking a wet sheet of newspaper& sticking it on the guy’s windshield on a cold day. Due to H-bonding he’ll never be able to scrape it off, unless he has access to hot water. Imagine writing on the paper, “Revenge is best served cold.”

More to come.

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How to Maintain a Lawn Without Herbicides or Synthetic Fertilizer, Version 2

Although I can appreciate the benefits of grass around the home, I am not a big fan of big lawns. They demand lots of energy and water, and in return, our family, which consists entirely of humans, cannot eat grass. For this reason, we have devoted most of our backyard to a vegetable garden, shrubs, berries and fruit trees. Unfortunately, a borough by-law prevents us from growing tomatoes or other produce in front of our home, so I maintain a small lawn.

Here’s what it looks like today, in early September.

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Although not “impeccable” by conventional standards, it’s quite green, and yet it has not ever received any herbicide or pesticide in its entire 21-year existence. For the last 15 years or so, it has not received any synthetic fertilizer either. So how do I keep it green?

I add used coffee grounds to my lawn throughout the summer. In the spring I also spread a few composted chicken manure pellets with my backyard’s compost in areas that have mostly grass. It also gets some urea(a nitrogen-source) from dogs who pee on my front yard during the winter. What’s wrong with synthetic fertilizer? Aside from being expensive, it inevitably spreads beyond the lawns’ borders, eats away at sidewalks, and runs off into our storm drains and river.

Next we come to the subject of “weeds”. Using such a term demonstrates ignorance of botany, which is a beautiful but underappreciated science. By not using herbicide, I save money, don’t risk health effects and allow plants like bird’s foot trefoil (Lotus corniculatus) to survive. Before flowering it looks like this patch from my lawn:

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It is a legume so it provides some of its own fertilizer thanks to a bacteria in its roots. If I don’t mow the lawn for a while, the trefoil produces attractive flowers that look these:

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Other non-grass plants worth tolerating are herbs like oregano, which spread to the lawn from the rock garden. If you look carefully, there is also parsley at the bottom center of the picture.  P1170382.JPG

There are three plants that I treat as “weeds” because they would otherwise grow at the expense of the grass, oregano and trefoil. They are dandelions, plantain and crab grass. To remove dandelions and their entire root, I use a tool. But trefoil does compete with them nicely. The other two have shallow root systems and are easy to pluck out with my thumb and index:P1170378.JPG

These were removed a little late. They have flowered and could have already spread their seeds. It’s best to learn to recognize them and pull them out earlier and donate them to the compost pile.

To encourage a deeper root network, I rely on rain, and even during dry spells, I water grass only every second day.  To conserve more water I use some water from a rain bucket positioned below the roof gutter. Since the patch of grass is only about 300 square feet, it takes me less than 15 minutes to hose it down.

Hopefully, if you haven’t already adopted similar practices, you will now be willing to save money, learn some botany and spend a little more time outdoors.

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