Posts
Another way in which a good sounding idea for science education has been poorly executed on average is the introduction of hands-on science. Ideas are supposed to be learned through doing experiments. However, textbook quality is generally quite low, and when executed by the average science teacher the experiments become mindless tasks, rather than learning experiences.
I have two daughters going through public school education in a relatively wealthy county in CT (so a better than average school system) and I have not been impressed one bit with the science education they are getting. Here is an example – recently my elder daughter had to conduct an experiment on lifesavers. OK, this is a bit silly, but I have no problem using a common object as the subject of the experiment, as long as the process is educational. The students had to test various aspects of the lifesavers – for example, does the color affect the time it takes to dissolve in water.
The execution of this “experiment” was simply pointless. They performed a single trial, with a single data point on each color, and obtained worthless results that could not reasonably confirm or deny any hypothesis. By my personal assessment, my daughter learned absolutely nothing from this exercise, and afterwards complained that she was becoming bored with science.
Friday, December 4, 2009
Teaching How Science Works, by Steven Novella MD at Neurologica Blog
Dr. Novella discusses particular curricula, and then makes an observation based on his childrens' experience.
Subscribe to:
Post Comments (Atom)
57 comments:
Amen. Hands on activities are a great part of science instruction, but they have to be surrounded by good context-creating instruction. The 4-week field science summer school sessions at our high school, for example, are preceded by a year-long series of readings and meetings, and can't be taken until the students have already had biology and/or chemistry.
Science instruction is worse than math instruction in this country, no doubt. Elementary teachers haven't the faintest idea what science is. They have no ideas what scientific ideas are important. They have no idea what's true physically or chemically, and their intuitions misleads them. They don't have the beginnings of an understanding of how to explain scientific principles simply because they don't know any.
Everything Wu has said about what's needed to fix math is needed to fix science. But we are a long long way off from fixing that.
I don't think I've seen one single textbook that focused on teaching the top 20 scientific ideas/principles/discoveries/inventions. Not ever. Just as history books once taught those things, science textbooks should too. They should be recitable the way the 50 states are, or the way dates of the American revolution are.
I wonder if anyone has ever created such a curriculum anywhere for k-8. Heck, it's not even how bio, chem and physics are organized in most high schools.
It's been long enough now I don't remember PS science classes. Since they were held in regular classes they were probably pretty basic or biology/physics based, not chemistry (messy compounds).
A friend of mine teaches BioChem in Univ. When we were in highschool in Chem we were taught, "should you over titrate, you figure out how to calculate the equivalent amounts of the other compounds." They can't do it. They want to throw out everything and start again. Now she has to teach them at the beginning of the year how to cross multiply and how to fix mistakes. Basic math.
She also tells me that there are double bell curves. The bottom 25% she needs to fail - lower curve... they won't let her fail more than 5% of them.
Remember the days of being told "look at the person on your left, the person on your right, they won't be here...." no more. Now we shove them through Univ too.
The equity priorities of the NSF- funded Math and Science Partnerships and the Centers for Learning and Teaching have produced many of the math curricula: Everyday Math, Investigations, MathLand, Connected Math, CorePlus, that are notoriously poor.
The same hostility to deductive logic pervades the science programs actively being pushed and funded.
The idea being advocated with cash grants was the need to change the nature of math and science in this country to focus on inductive "reasoning". The idea was that minorities and women would be better performers then. Closing achievement gaps among demographic groups became more important than math or science knowledge.
Solid, sequential foundations can be a barrier to equal participation in math and science for all.
The next step in math and science seems to be that any activity or task involving observation can be written up and labelled math and science. Everyone can now participate.
Does anyone think the Common Core Standards Initiative will be anything other than more of these anti-content classroom activities?
The national PTA says in its news releases that the proposed standards will "ensure equity". That usually means everyone mediocre together.
Yeah, science education is bad, especially in K-6. I spend a fair chunk of time with the freshman trying to overcome misconceptions they were taught in high school chemistry, and often Biology is worse.
As for NSF-developed curricula, the NSF writes grants to ed schools, and the program officers are recruited from those same schools of education, so don't be fooled by their endorsement. The NSF is also really on the equity bandwagon, so are hardly going to be pushing rigor.
Anonymous wrote:
> Hands on activities are a great part of science instruction…
I wonder if that is so.
I’m not denying of course that a chem major needs to do lab work or that a biology or premed major needs to have done some dissections.
However, our kids and I have recently been reading about Thomson’s discovery of the electron and Rutherford’s discovery of the nucleus – two of the truly “great” experiments in physics: much of modern technology is built on those two experiments.
From what we have read, Rutherford had Geiger and Marsden doing the real lab work, and, apparently, Thomson himself was not much of a hands-on guy – the tech did the work with Thompson being the “idea” man.
Of course, Faraday and Galileo (as far as I know) did the real hands-on work: I’m not suggesting that all experimentalists were only “idea” guys rather than hands-on guys. And, of course, Rutherford and Thomspon were not complete aliens to the laboratory.
But it does seem to me that the ideas come first.
It’s hard to come up with any real experiments for grade school (we did build a Cartesian diver, which is pretty cool, but I’m not sure the kids saw the point of it). The “physics experiments for grade school” books I’ve seen tend to have pretty silly stuff.
And, even in high school… well, how many high-school kids see any point to what they are doing in chem lab? I really didn’t, although I was the top student in the class and knew a fair amount of chemistry beyond what was covered in class.
What I hear from university profs is that they basically expect to teach lab skills in the university anyway.
Do pre-university labs serve much real purpose besides amusement and showing the kids that we are not just making everything up? Both of those are fair goals, but if these are the real goals, it might be good if they were explicit.
I suspect that it would be better to learn to really understand in thorough detail great experiments that were historically important than to spend time doing experiments that are really a bit pointless. E.g., how on earth did the early chemists actually figure out molecular structures?
(If ChemProf is following this thread, I'd actually appreciate any readable references that answer that last question in detail: it seems to me that the historical development of chemistry, was, in a way, the most amazing of any of the sciences. You can see volcanoes and fossils, stars and planets, animals and plants, pendulums and falling objects. But chemists couldn't see atoms or molecules! How'd they figure it all out?)
Dave Miller in Sacramento
"Do pre-university labs serve much real purpose besides amusement and showing the kids that we are not just making everything up? Both of those are fair goals, but if these are the real goals, it might be good if they were explicit."
Yes, they are helpful not only as an interesting hands on tool but as a tool that teaches them to learn to think about what they just saw/did. Form a hypothesis and defend it, in proper scientific method. It teaches them how to make mistakes and how to correct them using proper mathematical techniques or in biology looking at your friend's frog b/c you've managed to mangle yours :)
Lab work is important, and if you want someone interested in a topic, usually you have to show them why.
For our nightly reading we're switching to Usborne books Shakespeare for my eldest as soon as he has finished Scholastics "A christmas carol". Introducing laughter, friends, ghosts, and wars, and murders and mayhem... in child speak... The "classical education" way. Science should/could be presented in the primary grades the same way. Make it interesting, relevant, and historically correct.
Dave,
What's an early chemist ? What year? I too would love to see some historical explanation for chemistry.
Newton was an early chemist--and chemistry was basically all alchemy to him, and most of his colleagues. Chemistry was about quicksilver and mining, gunpowder, etc. chemical reactions that they could learn to control.
Mendeleev invented the periodic table in 1864, which was after atomic mass was known.
re: the difficulties coming up with real experiments for grade school stuff: I totally agree. This is why I think *experiments* per se are the wrong thing to teach.
The 20 most important FINDINGS in science, though, are the right thing. For example:
1. prove the earth is round. Grade school students can do this by learning about shadows and angles at two different locations with as much geometry as they should be learning in 7th grade: similar triangles is enough.
2. learn how planets go around the sun. Prove how the angle of our axis results in seasons, etc. 3rd graders can learn this; 7th graders can prove we MUST be at an angle or else there would be no seasonal difference in sun density.
3. buoyancy
4. gravity's acceleration value does not depend on mass IS an actual performable experiment, but it requires tight controls to work.
etc. I think you and I could come up with the list of the 20 most important findings, set them historically in order, and create a grade school curriculum 100 times better than what's out there.
A quick perusal of state level science fairs shows that real "experiments in grade school" often come as a result of college level labs that the student's parents have access to, or the experiments are mostly dumb.
To the bigger point: ideas before experiments: yes, absolutely, at least for those who aren't already deeply masters in their field. You can't just randomly collect data and inductively come up with a hypothesis of any merit at all. You need to be deeply versed in truths in order to see what's a REAL anomaly in the first place. Ideas lead to good experiments, and "playing around" doesn't get you real ideas without mastery. You just can't tell what's a statistical outlier due to error or due to some interesting phenomenon without some really complete theories to explain the phenomena in the first place.
--Form a hypothesis and defend it, in proper scientific method. It teaches them how to make mistakes and how to correct them using proper mathematical techniques or in biology looking at your friend's frog b/c you've managed to mangle yours :)
This is harder to do than it sounds.
What's a hypothesis? Is forming a hypothesis for something Newton already proved true doing science? What if everyone knows it but you? What if it turns out your hypothesis is trivially true?
How is dissection of a frog a hypothesis? What kinds of hypotheses can you make about dead frogs that ever teach you about live ones?
Science to defend a hypothesis need not be "experimental" in the sense of needing a bunch of data points. Proving the earth is round is a good example. Separating out the issue of "experimental error is a problem; more inaccurate data points to overdetermine a solution can minimize error" is a really really sophisticated idea; iirc, the astronomers didn't quite get that at the beginning. Hooke was perplexed by it, I think.
There is value in teaching the concepts of accuracy and precision. I believe that it MUST be taught experimentally, in some sense. But it may be that that's about what the best experiments in chemistry can offer.
--Science should/could be presented in the primary grades the same way. Make it interesting, relevant, and historically correct.
I don't know what relevant means here, but I totally agree that grade school science from the classical method, where it's historically correct, is a great idea.
Teaching science historically sounds like what we do, right? I mean, we teach galileo and then newton and that's historical? We make them do some bean experiments, and that's Mendelian genetics; we make them float a boat, and that's archimedes, etc.
but usually there is no coherence to this; it's a collection of facts that's independent of the thoughts that showed why someone would think this way, or what they already knew about the world, to show why they were moving in this direction.
Almost never does one go to the effort of explicitly teaching science the way history is taught. I don't mean as a history of science, even. I mean teaching the 10 biggest science highlights the way we teach (or should teach) the ten biggest civilizations over time to grade schoolers, emphasizing when and where. Then, we go and reteach it at a deeper level. Same with science. Teach the biggest most important truths, teach what's true, explicitly define what's true, perform an "experiment" or thought experiment, and so forth, explain the prevailing view at the time, the phenomena that didn't fit the view, etc.
Even a first grader could learn why a wheel is better than not having a wheel and learn about work, energy, and mass in the process. same with a pulley.
farmwifetwo wrote:
> Form a hypothesis and defend it, in proper scientific method. It teaches them how to make mistakes and how to correct them using proper mathematical techniques or in biology looking at your friend's frog b/c you've managed to mangle yours :)
>Lab work is important, and if you want someone interested in a topic, usually you have to show them why.
Obviously, I do not disagree in principle: of course, science is based on empirical experiments or observations, and that fact is critically important to the stunning success of science. I doubt anyone here denies that.
I’m honestly not sure how to implement what you said in practice, though. It’s especially hard in grade school, but, as I said, even in high school, the only thing I remember learning from labs is that I could manage to do them despite the fact that I am all thumbs (I suppose this is because I actually did have a very good understanding of the underlying science). I suppose that increasing my self-confidence a bit was worth-while, but… I can’t think of anything else I got out of the labs.
Your facetious example about the frog sort of makes my point – yeah, I managed not to get any of the frog innards in my mouth, unlike my lab partner (long story).
You also wrote:
> For our nightly reading we're switching to Usborne books Shakespeare for my eldest as soon as he has finished Scholastics "A christmas carol"
Try looking at DK’s “Voyages through Time” history series written by Peter Ackroyd: it has the usual beautiful DK illustrations, and Ackroyd is a much better writer than most of the DK folks. My kids fought over who got to read them out loud as the rest of us followed along silently. I think you’ll like them.
And, you’ve reminded me to start on Shakespeare, and ‘tis a good season for Scrooge and Tiny Tim too, eh?
Thanks.
All the best,
Dave
Allison wrote to me:
>What's an early chemist ? What year? I too would love to see some historical explanation for chemistry.
>Newton was an early chemist--and chemistry was basically all alchemy to him, and most of his colleagues. Chemistry was about quicksilver and mining, gunpowder, etc. chemical reactions that they could learn to control.
Hi, Allison! By the way, I’ve been out of touch because we were on a lengthy vacation, and then I came back with a nasty bacterial infection that had me hospitalized (I’m fine now, though frantically trying to catch up on everything): I’ll send you an e-mail soon.
I had in mind the period from (I think) the late eighteenth century through the mid-nineteenth when (I think) they figured out that methane was CH4, that ethane was C2H6, and so on. This includes figuring out (relative) atomic masses, etc.: as I recall, Dalton thought water was HO. How’d they figure out that it was H2O? As I understand it, by the end of the nineteenth century, they had worked out some quite complex molecular structures, had a good understanding of the bonding capabilities of different atoms, etc. How’d they do it?
After all, you cannot see atoms (at least not before atomic-force microscopes, etc.).
I’ve found books that give a few bits and pieces of the story, but no source that straightforwardly explains it.
Perhaps, no one has written the whole story up, maybe because it is so complex as to be overwhelming, but it does seem to me one of the more amazing achievements in science.
It also seems to me that integrating that story with real chem experiments could make the experiments more meaningful.
Dave
Compared with what has been being done in recent decades, my ES science exposure was better - small-town school with none of the 1-4 teachers having college degrees. No kindergarten, 3 teachers from the old 1-year normal schools and one with 1-2 years of college. Looking back, those four teachers gave us a pretty decent 4-year beginning science program that played to the strengths and interests of each. In first grade, we did plants and birds - terrariums, parts of plants, photosynthesis, nutrition, heliotropism etc. shown by growing plants in various locations/conditions. Bird anatomy, nutrition, migration etc. In second grade, we did animal species and characterists - hatched butterflies, grasshoppers, hatched frog and turtle eggs (all of the above brought in by teacher or class), kept aquariums, turtles, grass snakes and mice. We had visting rabbits. Third grade was a combination of physical geography and geology - land forms, volcanos, earthquakes, kinds of rocks and minerals etc. Fourth grade was the solar system and planetary movement, the seasons, night/day,tides, climate etc. We also did things with magnets, force, gravity etc.
Beyond those sorts of things, I think that labs prior to high school are likely to be timewasters. I can see some labs at the college-prep level, but most should stay at the AP level. My kids' high school required successful completion of the appropriate honors science prior to double-period AP; those AP labs were good.
I second the comment that trying to make science "inclusive", "diverse" and/or "girl-friendly" seems to water everything down to the point that it's hardly science (or math). That ensures that no one gets the foundation they need.
I should add that all of the ES science I mentioned above had a heavy content base; the hands-on part was teacher-led and specifically tied to appropriate reading. I remember doing worksheets based on the reading.
Anonymous wrote:
> I second the comment that trying to make science "inclusive", "diverse" and/or "girl-friendly"…
It needs to be added that those who seriously use the phrase “girl-friendly” are being incredibly, unbelievably, inexcusably sexist! This is a place where “political correctness” has its use, and jerks who talk about making science “girl-friendly” should be bludgeoned quite mercilessly as being sexist pigs.
Newton’s laws of motion are “girl-friendly,” at least for serious, intelligent girls. Or, perhaps, we should say that no real science is either “boy-friendly” or “girl-friendly” if “friendly” means it can be learned easily or without serious effort.
I know of course that you were criticizing this nonsense, not endorsing it. But, having girls, I feel a need to vent when the issue comes up!
Dave
Tragically the most stereotypical sexist and racist presumptions you may ever read in print will be in the solicitation guidelines for some of these MSPs or the NSF plans for a new textbook series.
We need to be pushing solid math and science instruction for everyone. These weak textbooks and emphasis on the child discovering the lesson really leave the parent's education levels and attentiveness and affluence as the default on whether kids will be able to pursue science, engineering, or medical careers.
That's the least equitable outcome of all if "equity" is the true reason for these changes.
I am coming late to this party, but yes, the way they figured out chemical structures is cool. I wish I knew a good readable history, but the following link for benzene is pretty interesting (I think) and illustrative:
http://www.ch.ic.ac.uk/rzepa/mim/environmental/html/benzene_text.htm
Basically, it is fairly easy with weight measurements and some basic reactions to figure out the ratio of different atoms. Some other fairly simple processes, mostly involving gases, can be used to work out molecular weights, so you can figure out that benzene has even numbers of carbon and hydrogen atoms, and that it contains six of each. But figuring out structure from that took some leaps that were only confirmed with X-ray diffraction in the 20th century. I have my grandmother's early 20th century organic book, and some of the structures there are just plain wacky.
As for Dalton, he thought water was HO, but Avagadro figured out it was H2O at about the same time. Avagadro wasn't an important scientist at that time, so his insight was ignored for years. Another interesting story, of how culture and expectations can impact science and how consensus can be wrong!
http://www.chemistryexplained.com/Ar-Bo/Avogadro-Amedeo.html
As I said, science education in K-12 is awful. Most experiments are time-wasters, which isn't surprising. At the freshman college level, lots of times labs are not useful or feel disconnected from lecture. At my institution, we spend a lot of time trying to link lecture and lab, and making sure that the lab illustrates important lecture concepts. Given the equipment at a lot of high schools, it isn't surprising that the labs aren't great.
K-6 is usually worse -- there are some great demos out there that are really simple, but teachers don't know them. I go into my mother's kindergarten class once a year, and do the candle experiment: if you fill a pie plate with water, and put a candle in the middle, light it, and cover it with a glass vase, the candle goes out and the water fills the space left by the oxygen. They love it, and they get the basic idea, which is all I'm hoping for. In my opinion, K-6 science would be better if they would stick to getting a few key ideas across. Instead, they do way too much environmental stuff, or lots of random factiods, and don't have enough context, history, or fun experiments. One of the worst examples I remember was dropping water onto a penny to figure out how many drops it could hold. The idea was to illustrate surface tension, but the results were all over the place. It would have been better to go to the old standard of putting an oil film on water or floating a boat, then using soap to break the surface tension, but that wouldn't have "felt" quantitative enough.
Having said that, it is good for students to come in with a little bit of experience with glassware, etc. But it is better if they haven't been convinced that lab is a waste of time, which is what happens all too often.
Thanks, ChemProf.
Now, if you can just get one of your colleagues to actually write that book-length history of how the early chem guys did it…
I agree with Allison's point that it is shameful how little everyone knows of the history of science. I have a Ph.D. in physics, and, yet I am fairly clueless about the history of chemistry.
So, how clueless is the average guy on the street?
Dave
Allison wrote:
> usually there is no coherence to this; it's a collection of facts that's independent of the thoughts that showed why someone would think this way, or what they already knew about the world, to show why they were moving in this direction.
>Almost never does one go to the effort of explicitly teaching science the way history is taught. I don't mean as a history of science, even. I mean teaching the 10 biggest science highlights the way we teach (or should teach) the ten biggest civilizations over time to grade schoolers, emphasizing when and where. Then, we go and reteach it at a deeper level. Same with science. Teach the biggest most important truths, teach what's true, explicitly define what's true, perform an "experiment" or thought experiment, and so forth, explain the prevailing view at the time, the phenomena that didn't fit the view, etc.
I think one of the problems is that most (educated) people rightly see Bach/Mozart/Beerthovem, Shakespeare, etc. as among the great achievements of Western civilization, but too few see modern science and mathematics as among the greatest achievements of Western civilization. Of course, too few people also see that Euclidean geometry (in the broad sense – i.e., including Eudoxus, Archimedes, etc.) was one of the greatest achievements of the Greeks.
Anyway, I have been seriously trying to follow a course similar to what you suggest with our kids for the last several years. I have a detailed “metanarrative” (to steal a word from the pomo people) dealing with physics, which is of course the easiest science for me:
I. The mechanistic philosophy
A. Galileo et al. tried to mechanize/mathematize the physical world
B. Newton brought it to partial fruition, but required spooky “action at a distance” for gravity
C. Faraday came along with a different force (magnetism) and eliminated action at a distance with the field idea
Etc. (Maxwell, Einstein, etc.)
II. The search for the smallest pieces
A. Elements
B. Atoms
C J. J. Thomson and the electron
D. Rutherford and the nucleus
Etc. (Neutrons, neutrinos, quarks, superstrings, and so on)
III. Combining statistical mechanics, electromagnetism, and atomic physics leads to the quantum crisis
A. Planck and the ultraviolet catastrophe
B. The stability of atoms
Etc. (Einstein and the photoelectric effect, the quantum wave function, etc.)
I’m probably making this sound more complex than it is: we started early with Galileo and falling objects and the swinging chandelier at church (pendulum), with atoms and electrons, etc. As they got older, I filled in more details. Let me make clear that I did not expect first-graders to deal with Einstein’s equation for the photoelectric effect, even though the equation is fairly simple (it is not unreasonable to explain it to a fifth or sixth grader, for example).
The purpose is not to fill in details of history (though I try not to be actually wrong about the history) but rather to explain the historical logic by which the ideas developed.
There are some pretty good books aimed at grade-school or middle-school kids that can help explain a lot of what I have listed in my partial outline above.
It’s not hard for me to take this approach in physics, not too hard in astronomy, harder for me in chem, biology, and geology.
Incidentally, in discussing the broad sweep of human history, I also try to treat science as a really dramatic event in human history, similar to the rise of Christianity and Islam, etc.
Anyway, clearly some of us who think along these lines need to write up how we see such an approach working in detail. I’ll try to post more of the details of my approach to physics on my blog in the not-too-distant future.
All the best,
Dave
If you can find a used copy, Asimov on Chemistry is probably a good place to start integrating science and history. I have Asimov on Physics, and use his essay on entropy every year. I don't think anyone else has done as good a job in making the science accessible and the history interesting at the same time.
Dave -- you'll find it very hard in biology to do what you want, as most of bio is still at the stamp-collecting phase. There is something of a crisis in the field at the moment, as they are realizing that there isn't such a thing as freshman biology, since everything needs to build off of the chemistry.
I do like the classical approach of science as a four year sequence, integrated with history: biology/the ancient world; geology and astronomy/the middle ages and renaissance; chemistry/18th and 19th C; physics/20th C. In particular, as Allison notes, this means that you revisit each field three times, getting more in depth with each visit. However, this is purely a homeschooler thing. I don't know of any schools, and certainly not any public schools, that take this kind of systematic approach. Instead, it is caterpillars today and photosynthesis tomorrow.
I must be heading to bed, but will type more on this a bit later:
the ancient world knew SO MUCH about mathematics. Our hobbling of geometry has meant we don't know anymore that the ancient geometers knew everything we describe by algebra or analytic geometry using actual geometry. They knew a great deal of number theory for the same reasons. They knew the earth was round, and some of them had figured out (before it was then forgotten) heliocentricity. So while I understand your 4 year sequence, I'm not quite sure if it's the way I'd quite organize it. Some of the classical schools here seem to have some semblance of sanity in their science programs. I shall investigate a bit more what they teach,as they do Greeks and Romans the first time between k-4th, and do science alongside.
But I wouldn't say it's a pure homeschooling thing. I've found that there are (non public) schools that know what they need, and are desperate for someone to give it to them.
I will be looking for Asimov's books, thank you. I have such a terrible knowledge of chemistry, myself, having never taken any while at MIT (we could take a solid state mat sci course instead), and never really learning anything but redox in high school.
re: biology: it depends what you mean. if instead of integrative bio, you look at Darwin, then the rise of understanding the cell, the tensions between genetics vs. cell environment work, for lack of a better term, with the rise of Watson and Crick/DNA/RNA/proteins and later mediation of those proteins ala McClintock, you can get to cellular respiration, krebs cycle, etc. in an interesting way.
And molecular biology, which is one of the only fields right now where there is an actual need to write new textbooks, because what's known is changing so fast that a 3 yr old book is wrong. but certainly, that's not a chemistry free route.
dave, I have a million more comments, but no time to let them percolate now. will do so more!
I would suggest though going back before Galileo for the mechanistic beginning, and you've reminded me of one of the questions I wish I'd ever had answered: but WHY is it an r-squared law? Once you've got an r-squared law for gravitational pull (and for electric fields), all sorts of beautiful things happen, like 0 divergence etc. and you only need to consider the mass(or electric charges) within your surface integral, etc. but WHY? Is there an explanation short of gauge theory?
And don't forget relativity! no reason at all that a high schooler can't do Wheeler's Spacetime Physics, or do elevator thought experiments.
okay, really, must percolate.
Allison wrote:
>I would suggest though going back before Galileo for the mechanistic beginning…
Yeah, I think you’re right, but my own knowledge sort of starts with Galileo – I’ve heard of the “Oxford Calculators” (Bradwardine et al.), for example, but don’t know much about them (for those who have never heard of them at all, these were medieval scholars who were starting to stumble onto the ideas of calculus – I’m of course oversimplifying due to my ignorance).
I do have the impression that the medieval fascination with clocks (and I mean not just simple clocks, but those bizarrely complicated mechanism that put out mechanical dancers and such periodically) had something to do with the rise of mechanism, but again I am exceeding the limits of my real knowledge.
I'm open to suggestions – I've been vaguely telling the kids that it started in the Middle Ages and then we jump to Galileo.
Allison also wrote:
> you've reminded me of one of the questions I wish I'd ever had answered: but WHY is it an r-squared law?
Short answer: in three dimensions for a massless particle carrying the force (photon or graviton), it just has to be. Longer answer: quantum field theory (and I’m not certain I have the field-theory answer down solid, though I really am supposed to know this!).
Yeah, I know, I’m the guy who claims that if you cannot explain it to a six-year-old at some level, then you do not really understand it yourself. Maybe dimensional analysis says something…
Allison also wrote:
>And don't forget relativity! no reason at all that a high schooler can't do Wheeler's Spacetime Physics, or do elevator thought experiments.
You don’t think they could just jump directly into Misner, Thorne, and Wheeler’s Gravitation? (Just kidding.)
Seriously, I agree.
At an earlier age, there is the whimsical book by Gamow, Mr. Tompkins in Wonderland. And, I learned special relativity at age twelve from Bondi’s Relativity and Common Sense (I taught myself a bit of algebra to understand the book – you don’t need much). And, Wheeler wrote a very nice popular book on general relativity for the Scientific American library.
There is lots of stuff out there in physics – now, if I can just learn some more chem…
Dave
ChemProf,
I’ve got Asimov’s World of Carbon scheduled as one of our science books for after New Year’s. What I know of organic chem (not much) comes from reading that as a kid.
I actually did not realize there was a book Asimov On Chemistry -- apparently it was published after I got out of high school.
Any other of Asimov’s books I should be looking at?
Thanks.
Dave
Dave -- There are a set of them taken from his columns in Fantasy and Science Fiction Magazine: Asimov on Chemistry, Asimov on Physics, Asimov on Astronomy. They are all good books, and I could imagine a nice middle school science course based on them, since they are very readable and not too mathy.
I actually think that's part of the problem with finding a good history of chemistry. In the 19th century, they were simultaneously figuring out atomic masses, chemical formulas, molecular weights, gas lawys, and the periodic table. All of this was highly mathematical and inter-related, which makes it challenging to write an engaging history (especially as those who write about the history of science aren't always interested in the math).
Allison: "re: biology: it depends what you mean. if instead of integrative bio, you look at Darwin, then the rise of understanding the cell, the tensions between genetics vs. cell environment work, for lack of a better term, with the rise of Watson and Crick/DNA/RNA/proteins and later mediation of those proteins ala McClintock, you can get to cellular respiration, krebs cycle, etc. in an interesting way. "
That's kind of my point though. You can't understand Watson and Crick of you don't understand bonding and intermolecular forces (especially hydrogen bonding). Similarly, you can't really get proteins if you don't understand bonding and basic thermodynamics. For all of this, you need at least a fundamental understanding of chemistry. I can't tell you how many students I have had who were taught, for example, that energy is stored in chemical bonds.
(For those who are saying "isn't it?" No, it isn't. If it were, then breaking a bond would release energy, but it takes energy to break a chemical bond. The idea usually comes from burning a fuel, but there the energy is released by the formation of the products, typically water and carbon dioxide. If breaking a bond released energy, every molecule would fall apart into atoms, and we'd be done.)
Oh, ChemProf, thanks for saying that. I was taught the same thing, that energy was stored in chemical bonds. I think everyone I know, even the chem majors, learned that and didn't get that misconception corrected until mid-level college chemistry, which meant BEING a chem major.
I think realized this was absurd earlier, and being a self absorbed ignorant adolescent, I therefore assumed all of chemistry was equally absurd and shunned it through all of college, not admitting til grad school that chemists knew stuff. (How many other idiotic students are mistaught something and get turned off, I wonder? I know I was dumb and arrogant, but I can't be the only one.)
That said, I am not sure I agree. I realll can't understand watson and crick without hydrogen bonding?
hm. I obviously don't understand hydrogen bonding (either chemically or any other way, as my quantum computing research led me to believe physicists and CS folks hadn't the faintest idea how a hydrogen bond worked, for all of our claims about how to make one a qubit) but isn't it possible to learn this stuff at a simpler level?
Is it possible that because you're a chemist, you believe it is all really necessary, but instead, reasonable simplifications could be made, just as they are in other subjects--like rational numbers as the basis for all math in high school, rather than the reals?
I will ponder. Certainly, the person who could simplify it properly actually must know it; I wouldn't have the skills at all to know what simplifications were reasonable.
Sure, Allison. Why is DNA a double helix? Why do the bases link up? Why do they zip and unzip? That's all hydrogen bonding. Otherwise, it just becomes a lot of factoids, or black boxes, and you wind up with misconceptions that cause you problems later.
Now, you don't need a deep understanding of a hydrogen bond. I can teach anyone who understands lone pairs what a hydrogen bond is to a simple level. (And as you noted, hydrogen bonds can be more complicated when you get into the details) But if you don't know that carbon is tetrahedral and you can't draw a basic structure for water, you can't understand DNA.
A few years ago, my colleagues tried experimenting with a pre-first year Bio course. They thought they could teach it without chemistry, but almost immediately they started writing reactions on the board, say for photosynthesis or respiration, for students who had no idea what a compound was. Unless you want to stick to "critter bio", you need to understand some chemistry first.
There's no reason high schools shouldn't teach chem first anyway, so we're in agreement there. chem, coupled with Alg II, then bio, then physics. if you did Alg I in 8th grade, it wouldn't be a problem at all.
but how simple can you make the chem ? Can a sixth grader understand a hydrogen bond well enough? I'm guessing yes, but that's because I've not thought about this problem for more than a few minutes.
Your point about misconceptions is exactly right: k-8 science should present the truth as clearly as possible, as simply as possible, but not "so simply" as to be untrue, or to lead to misconceptions. False cute analogies are devastating to undo.
So what chemistry a) needs to be taught to a 6th grader in order to make a 7th grade bio class meaningful, and b) can be taught to a 6th grader without introducing misconceptions?
ChemProf, Where *is* chemical energy stored? (And what does ATP have to do with energy???) I'm a non-scientist who is trying to make my son's 7th grade biology more meaningful to him. (and to myself, who found it so nonsensical and arbitrary back when I was in grade school that it was, by far, my lease favorite subject--and something that I, as Allison with chemistry, had absolutely no interest in pursuing in college).
I'm not sure you have to teach chemistry as early as some commenters are suggesting. If science teachers (especially biology teachers/curriculum) focused on systematics rather than the underlying biochemistry, there would be no need, in K-8.
Katharine wrote:
> Where *is* chemical energy stored?
At the risk of a physicist foolishly sticking his foot into chemistry:
First, technically, chemists tend to deal not with energy but with “enthalpy” or Gibbs free energy.
This takes into account entropy (i.e., the fact that greater randomness drives the reaction) as well as atmospheric pressure.
Ultimately it is really all entropy (Second Law of Thermodynamics) that is in control, and I really think it should be taught that way.
Second, yeah, there is energy in molecular bonds, but, it is really differences in energy between the initial and final states that actually matter, and you have to take into account not just the electron energy in a single atom, but the whole structure of the bond (i.e., both atoms) and sometimes even more of the molecule than that (the classical case is resonance all around a benzene ring).
I’ll give a concrete example: naïve texts tend to say that oxygen grabs an electron from hydrogen because the electron has a lower energy around oxygen than around hydrogen. No, it doesn’t. But if it is shared between oxygen and hydrogen, “spending more of its time” near the oxygen atom, then the energy is lower than if it were in hydrogen alone with no oxygen nearby.
Of course, “spending more of its time” is short-hand for a description of the quantum wave function, and, properly, one should speak of the total molecular orbital (which of course no one can actually calculate exactly) and so on.
So, the whole picture involves details of quantum mechanics. But, since no one can calculate those details exactly anyway, a bit of hand-waving is more than fair.
Anyway, the energy issue is not all that complex once one realizes that one is talking about differences between initial and final configuraitons.
Now… what is still bugging me is the intermediate case between “pure” ionic bonds and “pure” covalent bonds: part of the answer is that there are no pure ones, and you should just trust in quantum theory. But I still do not completely see how it works intuitively.
Another peeve of mine is “activation energy”: this is actually a kludge (albeit very useful, as all good kludges are) that obfuscates a bunch of different issues involving molecular configuration, statistical mechanics, wave-function overlap, and a lot of other stuff. I take it there has been a lot of work on this in recent decades, and of course the real answer is “Trust in quantum mechanics.” But, that “real” answer is useless, since no one can exactly solve the equations quantum mechanically.
So, even though chem is “really” physics (just trust in quantum mechanics!), you can see why it gives all us physicists headaches!
Dave
ChemProf wrote to me:
> I actually think that's part of the problem with finding a good history of chemistry. In the 19th century, they were simultaneously figuring out atomic masses, chemical formulas, molecular weights, gas lawys, and the periodic table. All of this was highly mathematical and inter-related, which makes it challenging to write an engaging history (especially as those who write about the history of science aren't always interested in the math).
Of course, that is precisely why such a book would be interesting to guys like me!
I have a vague idea of how it works: i.e., you assume water is HO, you assume some structure for methane, and then when you try to work out the stoichiometry for burning methane, things don’t agree with experiment and you go back and revise your assumptions.
But no doubt my vague description is rather off-base and the real story is more interesting; hence I’m curious as to how they really did it.
Dave
"If science teachers (especially biology teachers/curriculum) focused on systematics rather than the underlying biochemistry, there would be no need, in K-8."
Sure, absolutely, but as Katharine Beals pointed out, they don't. They want to teach metabolism and ATP, but don't want to teach the underlying chemistry so it becomes a bunch of memorized facts, plus bonus misconceptions.
ATP is a great example. ATP reacts with water, and the net reaction breaks one bond and forms two, so the reaction releases energy which the cell can use to drive other reactions. However, the "cartoon" version is ATP -> ADP + P which looks like a bond breaks to release energy, and which is translated into "energy is stored in chemical bonds". For a more detailed description, see
http://www.blobs.org/science/article.php?article=30
Of course, it is likely that the 7th grade teacher doesn't realize that this is incorrect, and would mark down a student who gave the correct answer, but that's another problem.
Dave's take is basically right (but enthalpy is essentially bond energy without entropy, while Gibb's Free Energy includes both enthalpy and entropy). Chemical energy is a biological concept that kind of mixes up enthalpy, free energy, and internal energy. It isn't really stored anywhere exactly. When you climb to the top of a slide, you can think of yourself as "storing" potential energy, which is then released as kinetic energy when you slide down the slide. However, if you get to the same height going up a hill, you have the same amount of potential energy, but don't think of it as "stored." In the same way, cells generate ATP which can then be used as a source of energy, but the energy is only released through a reaction. Biologists then say the cells are storing chemical energy.
Dave: "Now… what is still bugging me is the intermediate case between “pure” ionic bonds and “pure” covalent bonds: part of the answer is that there are no pure ones, and you should just trust in quantum theory. But I still do not completely see how it works intuitively. "
That one I do get intuitively, but "ionic bonds" is another misnomer -- I find it better to teach students that ions interact electrostatically. There are pure covalent bonds, but only for molecules where the atoms have the same electronegativity, which pretty much means they are the same atoms. Otherwise, one atom will "pull" on the electrons more than the other and you get polar bonds. Of course, polar bonds don't mean polar molecules, but that's another story, and way more than anybody but Dave wants to know in this thread!
I'd agree about Activation Energy (whenever you see energy without a modifier in chemistry, you can be sure it is a kludge!), although you can get at the activation enthalpy and entropy, which is somewhat more meaningful.
Allison, yeah, I think you could teach hydrogen bonding at a middle school level successfully. It helps that water has hydrogen bonding, which is why it has such a high boiling point and why ice floats. At a molecular model level, you could definitely get the main idea across, and then talk about biological systems a lot more systematically.
By the way, I do know what you mean about the ancients -- you could make as good or better an argument for tying astronomy to the ancient world rather than biology. But I still like the idea of the cycle, since if you did Chem is 6th or 7th grade, when you get back to high school biology, you can really do something.
ChemProf,
Sorry for messing up enthalpy and Gibbs free energy (I mentioned the danger of a physicist talking chemistry!).
I always liked Helmholtz free energy myself (for everyone else, you forget the atmospheric pressure effect): as I recall, that is what tends to pop up more naturally from the partition function, so it seems more natural to a physicist.
I’ll check out the ATP link: this has been bothering me too, since I knew the naïve explanation had to be wrong, but did not know what the correct explanation was.
Thanks.
Dave
ChenProf wrote:
> I'd agree about Activation Energy (whenever you see energy without a modifier in chemistry, you can be sure it is a kludge!), although you can get at the activation enthalpy and entropy, which is somewhat more meaningful.
I’m not denying that it is useful of course, but, if I understand correctly, when you start looking into temperature dependence, etc., you do start to see that it is a kludge (of course, I am out of my field here).
Dave
ChemProf wrote:
> That one I do get intuitively, but "ionic bonds" is another misnomer -- I find it better to teach students that ions interact electrostatically. There are pure covalent bonds, but only for molecules where the atoms have the same electronegativity, which pretty much means they are the same atoms. Otherwise, one atom will "pull" on the electrons more than the other and you get polar bonds.
Yeah, that I understand. But, of course, you cannot really separate the electrostatic effect from the wave-function itself – in the end, everything is in the wave function.
But I do see how you can do that as a good approximation.
What bother me is the “full-shell” way of thinking we were all taught. The double bonds in an O2 molecule give each atom a full shell because each atom sort of half-borrows the two electrons it needs from the other guy.
But in NaCl, we don’t think of the Na filling his shell, but rather the Cl just swiping the electron altogether for his outer shell.
I don’t see how to interpolate between these two cases: when does the atom with less electronegativty finally just give up on filling his shell and let the other guy have the electrons? When do you switch from both atoms achieving filled shells by sharing electrons to one atom losing his outer shell completely and the other atom filling his outer shell?
I know more or less how to do this in practice: C, N, O, and Cl never just give up their outer shell, Na always does, and so on.
And, I also know how the true answer works from quantum mechanics – bonding and anti-bonding molecular orbitals and so on.
But, I’m still confused conceptually, I think. Or put it this way: I’m pretty sure a bright university student could make me look foolish if I tried to teach this!
Dave
Thanks for your explanations, ChemProf and Dave; I now feel like I'm starting to get a bit of a handle on this. Any well-written layman's science book recommendations that would help further my understanding of energy in chemistry and biology? Ironically, it's been popular science books (Gould, Dawkins, Greene et al), not actual science courses, from which I've learned the most science, and learned to find science interesting. The more I think about it, the more I wonder how many thousands of people have been turned off to science over the decades by the way it's taught (and has been taught) in U.S. middle schools and high schools.
What does everyone think of the "physics first" movement? As I understand it, some high schools have upended the tradtional bio-chem-physics track in favor of physics-chem-bio.
On a separate note, are you in favor of "Earth Science?" Should a child who may do well in science at a college level forgo AP courses to fit in Earth Science?
Cranberry, we've discussed this before:
http://kitchentablemath.blogspot.com/2009/06/physics-first.html
Now, the "Physics First" movement from NSF is not only about physics first. It's about changing the methodology for how physics is taught. The "Physics First" movement is always paired with constructivist methods, "guide on the side", students leading the inquiry.
At the time of Steve's post, I hadn't heard of it, so I did some investigating. The source of the NSF funding for Physics First is really part of NSF's push into modeling instruction. Modeling instruction has a serious pedigree. I talked about it in a series of posts.
http://kitchentablemath.blogspot.com/2009/07/mastery-and-conceptual-understanding-in.html
http://kitchentablemath.blogspot.com/2009/07/physics-education-and-failures-in.html
http://kitchentablemath.blogspot.com/2009/07/physics-education-continued.html
http://kitchentablemath.blogspot.com/2009/07/more-modeling-instruction-techniques.html
Modeling instruction is an extraordinarily good way of teaching physics, but it requires an immense amount of physical knowledge by the teachers who teach physics, not to mention an immense amount of pedagogical skill. The PF movement is a long way from that, even as the modeling instruction part slowly increases. It's just that the PF movement grabbed onto some of the superficial level methods used in modeling instruction. They claim they do modeling, too. But given their students don't have any algebra 2, they won't be writing down any models for kinetic energy, motion under force, etc.
There's no reason to teach physics "first", other than that you want students who won't take more science to learn some. But what they will learn is nothing unless they've already got Algebra II as AT LEAST a coreq and probably a prereq where the students have mastered it.
there are plenty of good reasons to teach chem first then bio then physics. Chem then bio is good for all the reasons chemprof has discussed. Later physics improves the chances of the students having some real mathematical maturity. This is good because what goes wrong in teaching physics is their intuition. A common way to help students overcome their wrong intuition is to get them to look at what the math is telling them. but that means they have to know and understand what their math is saying, REALLY believe that the math is right, their calculation is correct, and realize what it implies.
There is no truth to the notion that teaching newtonian and maxwellian physics supports learning chemistry. No one is going to teach quantum mechanics to 9th graders in any way that would help a 10th grader understand hydrogen bonding. So the "chem rests on physics" part of the claimed rationale at this level is simply untrue. the physics it rests on isn't going to be taught in high school.
Unless you are at one of the premier high schools, the TJs or the Stuveysants, you should never forego an AP course in a possible desired college major.
Not because the AP test is useful or receiving college credit is useful.
It's because you should flatly assume any NON AP course in science is garbage until proven otherwise. The AP course may not be very good; your student may not learn much. But it is the only objective measure that what is being taught in that course meets minimal standards. (at a school like TJ or Stuy, maybe you can trust that all of the science classes are rigorous, I don't know.)
re: "earth science": I have no idea what that is. NONE. But I'd be highly skeptical of it being anything but global warming fraud.
what science is on the syllabus for such a course?
physical and historical geology, meteorology, ecology, astronomy,oceanography
I could post more, from the program of studies, but that would probably identify my district. From the description, it's heavy on lectures, reading, and "projects." Some laboratory work is mentioned, but I don't know how much time is devoted to that. The students apparently need to create web pages, videos, and write a research paper.
I should add, my kids won't be taking this course, as we're leaning to private schools for all our kids at this point. It's only that administrators and other parents will swear up and down that the course is "a wonderful course." I look at the descriptions I can find online, and think, I'd rather have my child in bio, chem, or physics, thank you very much.
Speaking of reversing positions, one high school in our area is looking at putting Algebra II before Geometry for the students who had algebra in 8th grade. The idea is to have more mature students prepared for a rigorous proof-based course in geometry. I want to see the details.
My study of Physics First indicated that the goal was not a better sequence, but to try and get more kids into science with motiational hands-on preliminary courses. There is nothing wrong with this in theory, but it usually means more fluff that the better students need to go through to get to the AP level. Supposedly, it increases the number of kids who eventually enroll in the AP classes. Perhaps. You can always slow down to improve education (presumably), so how much of it is due to slowing down and how much of it is because the sequence is reversed.
--physical and historical geology, meteorology, ecology, astronomy,oceanography
All in 180 days? (or in 90?) You could teach astronomy with some rigor in a semester, but not less.
I'm prepared to state emphatically that is garbage. Whether there is any rigorous oceanography or meteorolgy that could be presented in high school, it's impossible that you'd be doing all of this with any rigor at all.
But I'm sure students will feel great to know how they too can protect dolphins and sea urchins from mean people who run their showers too long.
Earth Science is a good course. In NY it's normally taken in 8th or 9th grade, depending on the district and how the honors program is run. It's a valuable course for those going into geology or materials science; however those students most likely have most of the content already absorbed from free reading and outside activities.
You can take a peek at the course here at Spring Valley H.S.'s site:
http://www.eram.k12.ny.us/education/staff/staff.php?sectiondetailid=16050
If I had a highschooler that doesn't know the content, I'd get the review book and go through it as time permits:
http://www.eram.k12.ny.us/education/components/scrapbook/default.php?sectiondetailid=37539&sc_id=1178593812
The remainder of the course is learning how to write labs up.
P.S. Little reading, no projects, daily lecture w/lots of visual aids and discussion time; 2 hr lab every other day. Observation and understanding of lunar cycle; observation and understanding of weather and symbols on weather map ( more in depth than BSA merit badge).
Very happy with kiddo's current instructor and would not trade course for Living Environment or AP Bio if 9th grader is an unorganized student as those two are heavy on memorization, while Earth Science is heavy on visualizing & understanding concept and observing phenomena.
Allison wrote:
>re: "earth science": I have no idea what that is. NONE. But I'd be highly skeptical of it being anything but global warming fraud…
Well, actually in our homeschooling, we’re finding the current “Climategate” incident to be of great educational value! It’s giving us a chance to talk about the dangers in computer programming (i.e., all sufficiently large programs still have bugs remaining), about scientific method (you have to check your model on *prospective* data, not just the past data that you “tuned” the model on), etc. Not to mention discussions about politics, the (mal)functioning of the mass media (CNN recently had “Bill Nye, the Science Guy” on as an expert on global warming!), etc.
So, if the teacher is actually literate in science (perhaps mainly homeschoolers), the topic of global warming provides truly wonderful educational opportunities across the curriculum.
(Incidentally, I’m really not taking a stand here on whether or not global warming is real, but merely pointing out that the current mess does indeed provide opportunities to talk about computer models, scientific method, etc.)
More broadly, I have seen a number of earth-science books whose coverage is quite orthogonal to climate-change issues – historical geology books, etc. My impression is that earth science in the public schools is very badly taught and aimed at kids not bright enough to handle the bio/chem/physics sequence, but I think that homeschoolers (or a bright classroom teacher who can take control of the curriculum) can actually make it a good course.
I do not have time right now, but I will try to post here or on my own blog a list of the earth science books we have already used and of ones we are planning on using in the future – there are some very good books out there, if you are not constrained by state Department of Education or local school-board approval.
And, the global-warming issue really can be of great educational value: I myself have been interested in the subject of global-climate modeling since the late ‘60s, long before the global-warming scare. The science is fascinating. Have you followed the work of Professor Richard Lindzen from you own alma mater? Lindzen is a brilliant (and honest) guy who is quite untainted by the current scandal. Indeed, he warned about the coming blow-up a year ago:
http://arxiv.org/ftp/arxiv/papers/0809/0809.3762.pdf
As bad as the current mess looks (and it may actually be even worse in reality than it looks), climate change is a legitimate subject of scientific study, and there are some honest guys like Lindzen in the field.
Admittedly, there needs to be a real housecleaning to get rid of the crooks.
Dave
Katharine wrote:
>Any well-written layman's science book recommendations that would help further my understanding of energy in chemistry and biology?
ChemProf has already mentioned Asimov on Chemistry which I will be getting shortly, and I’ve menitoned Asimov’s World of Carbon from which I learned all the organic chemistry I know (not much, admittedly).
Everyone with kids absolutely needs to get Mahlon Hoagland’s The Way Life Works one of the most brilliant intro science books I have ever seen, and relevant to the “physics first” issue. Hoagland was co-discoverer of transfer RNA, a world-class scientist. My kids truly loved this book, yet it has some material my wife, a Ph.D. in biology, did not know (discovered since she got her Ph.D.).
Hoagland thinks like a physicist (which of course I mean as a compliment): he treats biological systems from the bottom up as complex mechanical systems. I would not have thought it could be done at a child’s level, but he pulls it off: it’s no substitute for a good high-school honors course, but it may be the best-written science book for kids I have ever seen.
There is also an expanded “textbooky” version of the book: Exploring the Way Life Works : The Science of Biology. I’d get the brief version, and then move on to the expanded version if that seems to make sense.
At a high-school honors/AP level, I myself love Campbell, Reece et al’s Bilogy (this is *not* their “Concepts and Connections” book): Jane Reece is the “writing consultant,” but she also has a Ph.D. in biology, so you get a book that is nicely written as well as scientifically accurate. At a middle-school level, I like their Essential Biology with Physiology (“with physiology” matters – there is a version without physiology).
Hope this helps.
Dave
My take on Earth Science is that if it is in 8th or 9th grade, it may be reasonable, but I don't know that I'd give up a chance to take an AP course as a senior to do it. The project based stuff makes me nervous, though. If a student didn't take Earth Science what would they take instead? In this part of the country, Earth Science is a waste of time, but it sounds like the New York course is different.
And Dave, as far as the ionic bond issue, we are talking past each other, I think. This is a chemist/physicist thing. I look at sodium and say: this is the ultimate metal. It wants to get rid of that extra electron any way it can, so by the time it forms NaCl, it has already given up that electron to water or oxygen, or whatever it can find. Metals form positive ions and non-metals form negative ions or covalent bonds. Of course that's a simplification, since metals can form coordination compounds, but there they are just accepting electrons not contributing their own.
However, the physicist reads this and says, "yes, but WHY?"
Jumping back several days to the question of "how did the early chemists do it?", I happen to be in possession of an 1847 chemistry textbook by J.L. Comstock, entitled "Elements of chemistry: in which the recent discoveries in the science are included and its doctrines familiarly explained". This book is more than 20 years before Mendeleev published his first periodic table. (There's now a scan of it available on Google Books.)
Basically, the old dead guys noticed that elements always combined in certain mass ratios. From these ratios, they came up with combining numbers (which they called "chemical equivalents") for all of the elements. In just about every case, the chemical equivalent values published in my edition of Comstock turned out to be either the atomic mass, or exactly half of it. (They hadn't realized at the time that hydrogen was diatomic.)
In those days, the valence number of an element was its combining power--originally the largest number of atoms of oxygen that could form a compound with the element. (Recall that valence numbers were in use more than 50 years before the electron was discovered.) Of course, we now understand that the valence number is a direct result of the electron configuration. A lingering effect is that we still call the electrons associated with the highest principal quantum number "valence electrons".
ChemProf wrote to me:
>And Dave, as far as the ionic bond issue, we are talking past each other, I think. This is a chemist/physicist thing. I look at sodium and say: this is the ultimate metal. It wants to get rid of that extra electron any way it can, so by the time it forms NaCl, it has already given up that electron to water or oxygen, or whatever it can find. Metals form positive ions and non-metals form negative ions or covalent bonds. Of course that's a simplification, since metals can form coordination compounds, but there they are just accepting electrons not contributing their own.
>However, the physicist reads this and says, "yes, but WHY?"
Yeah, although of course, you and I both know “why” in a way: i.e., we both have a decent understanding of what goes on in the limiting cases (I’m glad that what you wrote does fit my own understanding!). What bothers me is how to get a smooth interpolation between those two extreme cases. As far as I know, this does not actually matter in practice: i.e., bonds seem to be either pure covalent (e.g., O2), covalent with some ionic character (many organic bonds), or strongly ionic.
You and I both know how to think about those cases (you better than I, of course), and it just is not a problem.
What about the case that is truly right in between – half covalent, half ionic, so to speak.
I guess the answer is it just does not happen, at least not often enough to be bothered about. And, if it does come up, do molecular orbitals, and all that.
So, in that sense, yeah, I guess I am saying, "yes, but WHY?" And, probably, the proper answer is “We chemists don’t need an answer to that question – sounds like one of those crazy things physicists insist on calculating.”
All the best,
Dave
"And, probably, the proper answer is “We chemists don’t need an answer to that question – sounds like one of those crazy things physicists insist on calculating.”"
Yep! Although a more accurate answer is that being ionic is like being pregnant -- you either are or you aren't. If you aren't, then you still have a polar covalent bond, right up until the electron transfers and then it is ionic.
Just realized I have an example for you, with numbers and everything! If you solve the quantum for HF, you find that the bonding orbital is 97% one of F's 2p orbitals and 3% the 1s orbital from H. But it is still considered a polar covalent bond, just a strongly polar one.
Reading parts of this thread reminded me of a website I had stumbled across once. http://www.vandammeacademy.com/store/default.htm
It is a private school selling a DVD of their physics class lectures. It looked interesting but was so obscenely expensive that I passed on it.
Their approach is to teach physics from a historical perspective and how each new discovery is built upon previous discoveries. It seemed worthwhile, but I couldn't swallow the cost ($1,000+) or their strong sales pitch.
Anonymous wrote:
> Reading parts of this thread reminded me of a website I had stumbled across once. http://www.vandammeacademy.com/store/default.htm
> It is a private school selling a DVD of their physics class lectures. It looked interesting but was so obscenely expensive that I passed on it.
> Their approach is to teach physics from a historical perspective and how each new discovery is built upon previous discoveries. It seemed worthwhile, but I couldn't swallow the cost ($1,000+) or their strong sales pitch.
I just stumbled upon this comment that I had missed on an older thread, but I feel I need to add an important caveat:
I know a great deal about the guy who put this together: he is a “physicist” (I use quotes because he is not a Ph.D. and has not done any legit research I know of) who thinks he has disproved Einstein’s general theory of relativity.
Without going into details, let me say that he is wrong, horribly, hilariously wrong – he has no idea what he is talking about.
I will not use words such as “fraud,” “crackpot,” etc., because I have reason to believe he is litigious.
If anyone knows about the Ayn Rand cult, he is deeply involved in this, including, I am told, the cult leader’s “research” disproving the Big Bang! I’m not attacking Rand herself (who died decades ago), but there does happen to be one group of her present-day followers who are truly bizarre, and this guy is a key figure in that group.
I would no more rely on this fellow for serious information about science than upon Deepak Chopra or Bill Nye the Science Guy (who was recently interviewed on CNN as a serious expert on global warming – Nye made a fool of himself, of course).
The VanDamme Academy sounds good until you dig deeper, and then… well, this group really does have a reputation for litigiousness.
So, I’ll just say:
Caveat emptor.
Dave
Post a Comment