This introductory physical chemistry course examines the connections between molecular properties and the behavior of macroscopic chemical systems.
Video 1.2 - Benchmarking Thermoliteracy
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From the course by University of Minnesota
Statistical Molecular Thermodynamics
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From the lesson
Module 1
This module includes philosophical observations on why it's valuable to have a broadly disseminated appreciation of thermodynamics, as well as some drive-by examples of thermodynamics in action, with the intent being to illustrate up front the practical utility of the science, and to provide students with an idea of precisely what they will indeed be able to do themselves upon completion of the course materials (e.g., predictions of pressure changes, temperature changes, and directions of spontaneous reactions). The other primary goal for this week is to summarize the quantized levels available to atoms and molecules in which energy can be stored. For those who have previously taken a course in elementary quantum mechanics, this will be a review. For others, there will be no requirement to follow precisely how the energy levels are derived--simply learning the final results that derive from quantum mechanics will inform our progress moving forward. Homework problems will provide you the opportunity to demonstrate mastery in the application of the above concepts.
Meet the Instructors
Dr. Christopher J. CramerDistinguished McKnight and University Teaching Professor of Chemistry and Chemical Physics
Chemistry
In the last video, I tried to kind of give you a sort of a big picture view of
the thermite reaction. And we talked about how the thermite
reaction was an analog for building a house.
It was a large scale process and when we have enough tools, we'll be able to
understand those large scale processes. Actually I'd like to maybe take an even
bigger picture of you and ask the question.
Why no thermodynamics? What's so useful about thermodynamics?
And I'll call this video, Benchmarking Thermoliteracy.
So, you're taking thermodynamics, right? And this is a course that enjoys a
certain reputation in higher education. So, if you remember your Dante, even
though I'm a chemist, I like to know a little something about classical
literature, you might be familiar with, lasciate ogne speranza, voi ch'entrate.
That's what inscribed over the gates of hell in Inferno, abandon hope all ye who
enter here. But, thermodynamics is worth studying,
even though it may be complicated, because it's such a powerful and useful
tool in chemistry, in physics, and all the physical sciences.
The first Nobel Prize in chemistry, in 1901, was awarded to Jacobus Henricus
van't Hoff, whose picture graces this slide.
And it was awarded for his contributions to understanding chemical equilibrium.
Some of you may actually recognize van't Hoff's name.
He's also quite well known for being the first to suggest tetrahedral carbon atoms
in organic chemistry. But his Nobel prize is for
thermodynamics. So, what's a thermodynamic principle that
you may even have encountered in prior work.
Here's an example of things that people will often look at in a course on
thermodynamics. Phase diagrams.
So, a phase diagram and the one that's showing here for carbon dioxide, tells
you, given a temperature, that's on the x axis, given a pressure shown on the y
axis, you can read across, and find within this diagram, what phase of matter
will carbon dioxide be. And so, if we pick a particular point
here, for instance, this is liquid carbon dioxide.
If we go down here to atmospheric pressure, which is about one bar, and we
go to a normal temperature. Our room temperature, which looks like
its right about here. It's a gas we know that.
It's one atmosphere. Carbon monoxide is a gas.
And then we know that it actually comes out as dry ice, as a solid.
It goes directly to the solid state when you get close enough.
This is all very interesting. But some people look at phase diagrams
and might say, yeah, I'm glad somebody knows that.
Ho-hum. However, understanding the phase diagram
for carbon dioxide is critical to actually using carbon dioxide for an
economically important process, and that is, dry cleaning.
So, it turns out that fluid carbon dioxide, whether as a liquid or a so
called supercritical fluid, and we'll learn a little bit more about
supercritical fluids in the not too distant future that fluid is useful for
removing dirt from clothing, for example. And the virtue of carbon dioxide as a
solvent in dry cleaning is that it can replace much less environmentally benign
fluids that would, otherwise, be used. Typically, say a chlorinated hydrocarbon
solvent. So, it was a chemist who actually
developed the use of fluid carbon dioxide for the dry cleaning process.
And actually we've got a picture of him here.
His name's Joe DeSimone. At the time that this picture was taken,
he was giving a talk at the University of Minnesota in 2003 and his affiliation
then was with the University of North Carolina.
And he was talking about CO2 technology, that is, how could you use knowledge of
supercritical or fluid CO2 in order to do a number of processes, with dry cleaning
being one of the most most economically important examples.
So, there's some thermodynamics in action in a very every day task.
I'd like to tell you another story about thermodynamics.
And in this case, I'm going to contrast that with a quote often attributed to PT
Barnum, most historians think it should actually go to someone named Hannum.
Maybe you know this quote, there's a sucker born every minute.
So, in 1979, there was an entrepreneur. His name was Joe Newman.
And, Mister Newman claimed to have invented an energy machine.
And in particular, the virtue of this machine was, no matter how much energy
you put in, you would get more energy out, you would create energy.
So, certainly this was something that was worth investing in.
It does turn out that the first law of thermodynamics, and we'll be discussing
the laws of thermodynamics, says, perpetual motion machines are not
allowed, which is another way of saying, you can't get more energy out than you
put in. And, the United States patent office
adopts a similar philosophy. So, in the 1980s, it turns out that
elected officials spent a lot of tax money trying to decide which of these two
mutually contradictory statements, I have a machine that creates more energy than
you put into it, or the first law of thermodynamics, could be true.
So, in 1911, the US Patent Office adopted a policy, and it says if you claim to
have patented a perpetual motion machine, you need actually to deposit it with the
patent office for at least a year. And they will look at it and if they
decide it is a perpetual motion machine, and they never have, then they'll give
you a patent. But Newman filed suit against the Patent
Office, and claimed that his energy machine wasn't really a perpetual motion
device, and so that regulation did not apply.
A judge who was appointed to hear the case, Judge Thomas Penfield Jackson,
decided he did not have enough knowledge of thermodynamics himself.
So, he appointed a special master, a former commissioner of patents, William
Schuyler, to investigate the machine. And to the surprise of the court,
Schuyler's report came back and said, no question about it, Newman's energy
machine, it's fabulous. Output of energy is greater than input.
The judge was not entirely persuaded, so he taught himself a bit of Physics.
God bless. eight months later, he decided that
Schuyler's report had to be erroneous. And in support of his position, he cited
the laws of thermodynamics. So, those aren't laws on the statute
books, but they're pretty important laws. he advised that the National Institute of
Standards and Technology in the United States could look at the machine.
But Newman's attorneys refused. And media attention to the case led to a
United States member of Congress, Representative Bob Livingston, a
Republican from Louisiana, hearing media reports and deciding that Newman was
clearly being unfairly treated. An abuse of power by the patent office.
And together with six members of congress, he sought a private relief bill
that would force the patent office to issue a patent to Newman.
So, congress did what it does in the United States, it held hearings.
And an expert from the Nat-, National Bureau of Standards, that's what NIST was
called back in those days John Lyons, testified before the committee and he
said various things. But, fundamentally, it came down to, you
can't get more energy out than goes in, and that's the first law of
thermodynamics. Newman was next to testify, and
unperturbed by the NBS expert, he cited Schuyler's report and he did what a
salesman does. He sold the device to members of the
Senate panel. And one of the members of that panel was
Senator John Glenn, shown here in the in an astronaut's outfit.
Those of you who remember John Glenn will remember he was an astronaut.
Democrat from Ohio, brought a little bit or reason to the proceedings but not
actually as a physical scientist. And in particular, Senator Glenn asked
Newman if he had known William Schuyler before he'd been appointed by the court
as a special master. And Newman was a bit flustered and said
he thinks they met once before but it was unlikely Schuyler would remember that.
At which point, Glenn pointed out it was, in fact, Schuyler's patent law firm that
had represented Newman to the patent office for the original filing.
And at that point, all the senators began sliding back from the table, sound of
chairs sliding, and that's the end of this story.
So, it's a bit unfortunate from my perspective that these senators in the
United States Congress were mostly lawyers and not really swayed by a
violation of the First Law of Thermodynamics but they certainly did
understand conflict of interest and that's what ended this case.
Clearly more scientific literacy, if you will, thermodynamic literacy within
society at large would be a welcome contribution.
So, let me talk about my goals for this course and what I hope are your goals for
the course as well. Lets learn how the Universe really works,
and that is what thermodynamics does. It provides us a set of tools to make
predictions about how the Universe works. And I hope to provide you with some of
those tools. We won't have time to develop all of them
perhaps, but at least some fundamental and useful ones.
A subgoal is to end up smarter than most politicians, and of course, the more
difficult goal here admittedly at first, but that's enough snarkiness.
In this video, let me tell you about what the course is going to look like.
So, there will video lectures, just like these and for many of the lectures there
will be self assessments embedded within them.
And when you take these self assessments, you will be able to click on a little
button, explanation, that will tell you why the correct answer to the self
assessment is what is is and we'll see that in maybe two videos from now.
I will also have some additional demonstrations, so if you were drawn into
the course by that wonderful thermite reaction, hopefully there will be one or
two others that are equally as exciting. And there will be a few that maybe won't
necessarily explode or catch fire, but are still pretty interesting and
illustrate key thermodynamic concepts. So we'll solve those throughout the
course as well. Every week, at the end of the week, there
will be a homework assignment. And those will be available two weeks
ahead and one week past the individual week in question, after which, they'll be
graded. They're ten questions each, and each of
the questions is worth ten points, so each homework will be worth 100 points,
and there will be eight of them, one for each of the eight weeks when content will
be presented within the course. There will be a final exam at the end of
the course and that exam will be worth 200 points.
And passing in this course will constitute 60% or more of the possible
1,000 points. So, that's 600 points or more.
And that brings us to the end of the thermal literacy video as well as
explaining what the course is going to look like.
In the next lecture that we see, we're going to address a critical physical
phenomenon that's going to let us derive some of the tools that we're going to use
in computing thermochemical quantities. And that is the quantization of energy
that describes how energy is stored in microscopically small systems.
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