Re: [Phys-L] strange things in chem book

[John Denker <jsd@av8n.com>]

On 09/22/2012 02:39 PM, Aburr@aol.com wrote:
> I  think he may have set a task too difficult for most high school 
> or general  physics students.

OK, my suggestion was "inelegantly stated".  That's the new euphemism
for something I really shouldn't have said.  Specifically: I shouldn't 
have called it "homework".  It doesn't make sense to tell students on 
Tuesday to come back on Thursday with a list of errors in the textbook.

The goal is to teach an appropriate level of skepticism and to make 
it a habit that will stay with them for a lifetime.  It is a skill 
that needs to be applied to everything they read, always, not just 
on National Skepticism Day.  Therefore making a list of bugs in the 
textbook is a long-term project, not a one-time homework assignment.

Also, what we expect of students at the beginning of the high-school
course is different from what we expect at the end of the college course.

> Oh, [the textbooks] have errors all right, and many have wording 
> that I would  prefer were different, but it takes a lot of time and a 
> sophisticated knowledge  of physics to spot true errors (as distinct from 
> oversimplifications).  

Sometimes it's not as hard as all that.  Sometimes all it takes is 
cross checking, which is something high school students are supposed to
know how to do.  For instance, if you are writing a report on Kashmir,
get a book on India and see what it says;  then get a book on Pakistan
and see what it says.  If you get two wildly divergent stories, you
know that at least one of them is slanted.

Nowadays, google and wikipedia make this kind of cross checking easy 
and quick.

Sometimes you don't even need two sources.  A typical HS chemistry
book gives a series of rules that define the difference between 
"chemical change" and "physical change", then gives a series of 
examples that are blatantly inconsistent with said rules.  Many HS
students are smart enough to notice this.  They generally won't
say anything about it, because they know what would just get them
into trouble.

Ditto for significant digits.  Typically AFAICT everybody in the room 
including the teacher knows that sig figs don't make any sense ... but
still they go through the motions of learning and teaching the topic.
This is the opposite and the enemy of critical thinking.

Returning to the theme of cross checking:  If the students are working 
a problem in class, don't let them stop at the point where they have
gotten the answer.  Insist that the job is not done until they have
made some consistency checks.  For instance, when resolving a vector 
into components, if a = c sin θ and b = c cos θ, then
 -- |a| had better be less than |c| (or equal in degenerate cases)
 -- |b| had better be less than |c| (..)
 -- |a| + |b| had better be greater than |c| (..)
 -- a^2 + b^2 had better equal c^2
 -- et cetera

The point is twofold:  (1) it helps to give specific constructive tactical
suggestions on /how/ to check the work, and (2) it helps to reiterate the 
general strategic point that checking the work is always important.

Starting from the idea of checking their own work, it is only a small step
to checking everybody else's work, including the textbook author's work.

A good textbook will point out connections, e.g. it could point out that 
equation 7.4 can be considered a special case of equation 14.2.  Most
introductory texts I've seen are astonishingly weak in this department,
but this is something you can easily fix by telling your class about
such connections when the opportunity arises.

Again the point is twofold:  You start by giving them some fish.  Once
they see the value of it, you gradually teach them to catch their own fish.
The goal is to get them to the point where /on their own initiative/ they
mull every sentence and every equation, asking themselves many questions
including: Where have I seen this before?  How does this fit in with other
stuff I know?  Or does it conflict with other stuff I know?

This brings us to the topic of metacognition.  Amazingly few students have
given anywhere near enough thought to thought.  Most folks on this list have
thought about it, but students have not.  The "study skills" resources available 
to students are all-too-often pathetically superficial, in the sense that they
tell you how to "schedule study time" and "how to control the study environment"
and all sorts of other epiphenomena associated with studying.  
  http://www.ucc.vt.edu/stdysk/stdyhlp.html
I'm not saying that those things are wrong or unnecessary, just that they are 
superficial.  They are necessary but nowhere near sufficient.  It's like a 
baseball coach who says that to play baseball you need a glove, and then 
devotes nearly all his efforts to describing the physical shape of gloves, 
and never gets around to explaining the strategy and tactics for playing 
the game, let alone the objective of the game.  I thought the aforementioned
web site might be OK when I saw a link to "Strategies to Use with Difficult 
Questions" ... but when I followed the link it turned out to only deal with
"difficult exam questions" as found on multiple-choice exams ... not real-
life questions.  Again, those "strategies" are not so much wrong as pathetically
superficial.  Anybody who thinks those techniques suffice for dealing with
difficult questions has never seen a truly difficult real-world question.

Here are what I consider some of the most often under-appreciated points:

*) There is not much distinction between memory and thought.  Memory itself
 _is_ a thought process.

*) Memory consists of two complimentary parts:
  -- Learning i.e. memorization, and
  -- Recall

*) It is almost hopeless to try to improve recall at the time when you 
 need to recall something.  It's too late.  Instead you should focus on
 improving learning and memorization.  This requires an investment.
 The investment (learning) is made months or years before it pays off
 (recall).

 To say the same thing another way:  You can't get something out of your
 memory in a effective way if you didn't put it /into/ your memory in an
 effective way.

*) Neurons are slow.  The cycle time is on the order of 15 milliseconds.
 This should make it obvious that the only way we get anything useful done 
 is via massive amounts of parallel processing.

*) As a consequence of the previous item, I am always shocked when some
 people on this forum emphasize "paying attention".  Many study-skills
 experts say the same thing, but it cannot possibly be anything more than
 the tiniest flea on the tail of the penguin on the tip of the iceberg.
 Conscious attention is serial, while roughly 99.9999% of all thought 
 is parallel and subconscious.

 Specifically, suppose you have a 25,000 word vocabulary.  If somebody asks 
 "what's this" and shows you a bunch of grapes, a fraction of a second later
 you say "that's a bunch of grapes".  You did *not* come up with that by
 serially, consciously, attentively running down the list of more than
 25,000 possibilities.  There wasn't anywhere near enough time for that.
 Not by several orders of magnitude.

*) This leads to the remarkable conclusion that when you consciously try 
 to make yourself better at learning and memorization, you are using your 
 serial conscious attentive mind to tell the other roughly 99.9999% of 
 your mind what to do.  It surprising that this is possible at all.  It 
 is not surprising that it is very hard.

*) We mentioned mulling.  It has been known explicitly since 1898 and 
 probably long before then that mulling is super-important as a means for
 laying down memories that will be useful later.  Mulling means checking
 each new idea to see how it connects with what is already known ... 
 and/or how it conflicts with what is already known.

*) There is a very fine line (or maybe no line at all) between mulling and
 daydreaming.  The kid who is not paying attention in class might well end
 up smarter and wiser than the kids who are paying attention.  The key skill
 is to daydream about useful things, not about last night's reality-TV show.

 A secondary but valuable skill is not getting caught.  If you're good at
 multi-tasking, you can daydream while /pretending/ to pay attention.  I 
 once read that Marie Curie was notoriously bad at this.  She would get so 
 lost in thought as to become quite unaware of her surroundings.  People 
 would sometimes exploit this to play pranks on her.

*) Every time you recall something, you make it easier to recall it the
 next time.  We started out by making the distinction between memorization
 and recall, but there is a feedback loop that blurs the distinction.  Let's 
 be clear:  Practicing the recall task is one of the key ways to perform 
 the memorization task.  That sounds backwards, but it works.  This is part 
 of what mulling does.

*) As I said yesterday:  Some of what goes into teaching critical thinking
 is hard ... but some of it is easy.  There is a lot of low-hanging fruit
 that we really ought to grab.

 Perhaps #1 on the list of low-hanging fruit is "don't teach wrong stuff".
 This is why this thread on "strange things" in textbooks has so much
 upside potential.  Every time the class gets mired in significant figures
 or chemical versus physical change or the five-step scientific method or
 all the other stuff that cannot possibly be true, it does incalculable
 harm.  It teaches students, for the Nth time, that critical thinking is
 not permitted in school.

 Conversely, this gets us back to where this message started.  This is why
 there should be a systematic long-term program to reward students for
 catching errors in the textbook ... and for catching errors in what was
 said in class.  Catching errors like this is not quite the definition of
 critical thinking, but it is one of the goals and one of the hallmarks.

> I would enlarge the 
> search domain to  include any printed material.

Agreed.  As yet another step in the same direction, it is amusing to ask
students to identify consumer products that could not possibly work the
way they are supposed to.  The drugstore offers a bonanza of such things,
including homeopathic cold remedies, copper-bracelet arthritis remedies,
magnet therapy, etc. etc. etc.

OTOH one should be careful not to go tooooo far in this direction.  I draw
the line at exposing students (especially at the introductory level) to
deceptive information that they would not otherwise have encountered.
Dwelling on a misconception oftentimes does as much to reinforce the
misconception as to dispel it.  The first order of business should be to
emphasize the correct ideas.  That will crowd out the misconceptions the
way a healthy lawn crowds out weeds.