Wednesday, Jan. 9, 2019
4 Non Blondes "What's Up"
(4:48), Tash Sultana "Jungle"
(up to about 7:10)
Information about this class and course requirements
1. We started class today with a quick look at
the Course Information
handout. You
should read through that information carefully on your own and
let me know if you have any questions or concerns (please let
me know also if you find any errors or typos).
A textbook is not required for this class. If you want a
different and more complete coverage of weather and climate than
you'll get in class, you're welcome to borrow one of the instructor copies of introductory
level textbooks that I have in my office. Just let me
know. Otherwise you should be able to do perfectly well in
the class by reading the online notes. You should read the
online notes even if you are in class.
A packet of photocopied ClassNotes is "required." The
notes will save you a lot of time writing and drawing in
class. You can buy the ClassNotes at the ASUA Bookstore
located in the Student Union. Last fall I also started
putting the ClassNotes
online. I'm able to use color in the online version,
the photocopied version is black and white (we'll add the color in
class).
Attendance isn't required and isn't taken in this class. The
expectation is that if you don't attend class you will read the
online notes and keep up that way. In the end many students
aren't able to do this and their grade suffers as a result.
2. Writing is
an important part of this class and is described in more detail
on the Writing Requirements
handout. Please have
a careful look at that also and let me know if you have any
questions.
The first half of your writing grade is an
experiment report. You only need to do one of three
different experiments, so think about which of them (listed on the
handout) you might like to do. I'll probably bring a signup
sheet to class on Friday. I may also try to bring some
Experiment #1 materials to class then also. Materials for
the other two experiments will be handed out at roughly 3-week
intervals.
The so-called One Side of One Page (1S1P) reports make up the second
part of your writing grade. Topics will appear
periodically during the semester on the class webpage. As
you write reports you will earn points (the exact number of points
will depend on the topic and the quality of your report).
Your goal should be to earn 45 1S1P pts, the maximum number
allowed, by the end of the semester.
You'll be allowed to revise and raise your grade on the first
draft of your experiment report. So you should be able to
earn a pretty high score on that. And, unless you
procrastinate, you can just keep on writing 1S1P reports until
you've earned 45 points. There's no reason not to earn a
high writing grade. The writing grade gets averaged in with
your quiz scores and, as the example below shows, can have a
significant and beneficial effect on your overall grade.
Grade example
Your final grade in this class will depend on your quiz scores,
how much extra credit you earn (from optional take home and in
class assignments), your writing grade, and (perhaps) your score
on the final exam. A sample grade report from the 8:00 -
9:15 am Tue/Thu section of the Spring 2018 class is shown below
(most of the numbers are class averages).
Doe_J
quiz scores
[Practice Quiz] 59%
quiz1 71%
quiz2 72%
quiz3 70%
quiz4 77%
writing scores
writing scores: 32.0 (expt/book report) + 45.0 (1S1P pts)
writing grade: 96.3%
2.5 EC points (3 pts possible)
extra
credit earned on optional assignments
overall
averages (prior to the Final Exam)
average (no quiz scores dropped): (71 + 72 + 70 + 77 + 96.3)/5 +
2.5 = 79.8%
average (lowest quiz score dropped): (71 + 72 + 77 + 96.3)/4 + 2.5
= 80.8%
Final exam score: 77.5%
Overall grade:
80.8% x 0.8 + 77.5% x 0.2 = 80.8% (B)
The 4 quiz grades are shown at the top.
A score of 32 points (out of 40) on the experiment report
and 45 1S1P points resulted in a writing percentage grade of
96.3%. There's no good reason not to end up with a writing
score close to 100% (or even greater than 100%)
Students that did turn in the Optional
Assignments earned on average 2.5 pts of extra credit during the
semester. You will have the opportunity to earn at least 3
extra credit points.
The overall average without any quiz scores dropped is
shown next. The result, 79.8%, is less than 90.0%, so the
average student last fall did have to take the final exam
The second average (with the lowest score dropped) is a little
higher, 80.8%.
If you do well on the final exam it will count 40% of
your overall grade (trying to maximize the benefit it can
have). If you don't do so well on the final it only counts
20% (minimizing the damage it can cause). In this example
the final exam score (77.5%) was lower than the 80.8% value, so
the final exam only counted 20%. The overall grade was was
80.8% a B.
Here's the amazing thing: even
with C grades on each of the quizzes and a C on the Final Exam you
could well end up with a B in the class. That is possible
when you have a high writing grade and also have some extra credit
points.
"Chapter 1" - the earth's atmosphere
We did cover a little course material on this
first day of class so that you can get an idea of how that will
work (I'll try to not cover any new material on the last day of
class in May).
If we were using a book
we'd start in Chapter 1 and here's some of what we would be
looking at
We will come back to the first item, the composition of the
atmosphere, today.
Here's something to try.
As you leave the building after class look around, take a deep
breath of fresh air.
Could you see the air?
Air is mostly clear, transparent, and invisible. Most
gases are invisible. Sometimes the air looks foggy,
hazy, or smoggy. In those cases you are probably
"seeing" something else such as small water droplets or ice
crystals (fog) or small particles of dust or smoke (haze and
smog). The particles themselves may be too small to be
seen with the naked eye (just like air molecules) but are
visible because they scatter (redirect) light.
Scattering of light is a pretty important concept and
we will learn more about it soon. Air molecules scatter
light so air isn't really invisible. If you shine a
bright light through enough air (for example sunlight shining
through the atmosphere), the air (the sky) appears blue.
This is a little more complicated form of scattering of
sunlight by air molecules. We'll come back to this later
as well.
Could you
smell the air?
I don't think you can smell or taste air (air containing
nitrogen, oxygen, water vapor, argon and carbon
dioxide). But there are also lots of other odors you can
sometimes smell (freshly cut grass, hamburgers on a grill,
etc). I don't consider these normal constituents of
the atmosphere.
You can probably also smell certain pollutants. I
suspect our sense of smell is sensitive enough for us to
detect certain air pollutants even when their concentration
is very small (probably a good thing because many of them
are poisonous).
Natural gas (methane) used in hot water
heaters, some stoves, and furnaces is odorless. A
chemical (mercaptan) is added to natural gas so that you can
smell it and know when there is a leak before it builds up
to a concentration that could cause an explosion.
It is harder to answer this question.
We're always in contact with air. Maybe we've grown so
accustomed to it we aren't aware of how it feels. We can
certainly feel whether the air is hot or cold, but that probably
has more to do with energy flowing between us and our
surroundings. And we can feel wind.
In a couple of weeks we will learn that air pressure is pressing
on every square inch of our bodies with 12 or 13 pounds of
force. If that were to change suddenly I'm pretty sure
we'd feel it and it would probably be very painful.
2 objectives for today:
1. You should be able to list the 5 most abundant gases in air
and say something (maybe more than one thing) about
each of them
2. You should be able to say something about dew
point temperature
1. The 5 most abundant gases in our atmosphere
Let's start with the most abundant gas in the atmosphere. I
poured some of that material (in liquid form) into a Styrofoam
cup. Here's a photo I took back in my office.
You can see the liquid, it's
clear, it looks like water. Probably a lot of you
knew this was nitrogen (liquid nitrogen).
Liquid nitrogen is very cold and begins to boil
(evaporate) at -321o
F.
The most abundant gas in the earth's atmosphere is
nitrogen. We'll use liquid nitrogen in several class
demonstration this semester mostly because it is so
cold.
Nitrogen was discovered in 1772 by Daniel Rutherford (a
Scottish botanist). Atmospheric nitrogen is relatively
unreactive and is sometimes used to replace air in packaged
foods to preserve freshness. You don't really need to
worry about remembering details like this.
Oxygen is the second most abundant gas in the
atmosphere. Oxygen is the most abundant element (by
mass) in the earth's crust, in ocean water, and in the human
body. In liquid form it also becomes visible.
Some photographs of liquid oxygen (O2)
are shown above
(it
boils at -297o F).
It has a (very faint) pale blue color (I
was pretty disappointed when I first saw it because I had
heard it was blue and imagined it was a deeper more vivid
blue). When
heated (such as in an automobile engine) the oxygen
and nitrogen in air react to form compounds such as
nitric oxide (NO), nitrogen dioxide (NO2),
and nitrous oxide (N2O). Together as
a group these are called oxides of nitrogen; the first
two are air pollutants, the last is a greenhouse
gas. I'd
love to bring some liquid oxygen to class and
it's probably available on campus but you
probably need to be careful with it because it
is reactive.
I recently learned that liquid ozone (O3)
does have a nice deep blue color.
Liquid ozone (source
of this photograph).
Sorry I don't
have any liquid ozone which is probably a good
thing because it's also very (probably
dangerously) reactive. Ozone gas is also
poisonous.
Here is a complete
list of the 5 most abundant gases in air. And a note about the figures you'll find in these
online notes. They may differ somewhat from
those drawn in class. I often redraw them after class, or
use neater versions from a previous semester for improved clarity
(and so I can get the notes online more quickly).
With a little practice you should be able to start
with a blank sheet of paper and reproduce the list above.
Water vapor and argon are the 3rd and 4th most abundant
gases in the atmosphere. A 2% water vapor concentration is
listed above but it can vary from near 0% to as high as 3% or
4%. Water vapor is, in many locations, the 3rd most abundant
gas in air. In Tucson most of the year, the air is dry
enough that argon is in 3rd position and water vapor is 4th.
Water vapor and carbon dioxide are circled because they are
greenhouse gases.
Water vapor, a gas, is invisible. Water is the only
compound that exists naturally in solid, liquid, and gaseous
phases in the atmosphere.
Argon is an unreactive noble gas (helium, neon, krypton, xenon, and radon are also inert gases).
Here's a
picture of solid argon ("argon ice"). It melts
at melts
at -309o F and
boils at -302o F;
it's doing both in this picture. (image source).
Here's a little more
explanation (from Wikipedia)
of why noble gases are so unreactive. You can gloss over
all these additional details if you want to, none of this was covered in class.
The noble gases have full valence electron shells. Valence electrons are the outermost electrons of an atom and are
normally the only electrons that participate in chemical bonding. Atoms
with full valence electron shells are extremely stable and
therefore do not tend to form chemical bonds and have little
tendency to gain or lose electrons (take electrons from or
give electrons to atoms of different materials).
Noble gases are often used used in "neon signs"; argon
produces a blue color. The colors produced by Argon (Ar),
Helium (He), Kryton (Kr), Neon (Ne) and Xenon (Xe), which are
also noble gases, are shown above (source
of the images). An electric current is
traveling through and heating the gas in the tube causing it to
emit light. You're seeing the light emitted by the gas
itself. The inert gases don't react with the metal
electrodes in the bulbs.
Fluorescent bulbs (including energy saving CFLs) often also
contain mercury vapor (which means you should properly dispose
of them when they burn out). The mercury vapor in CFL
bulbs emits ultraviolet light that strikes a phosphor coating on
the inside of the bulb causing it to fluoresce (emit visible
light). Different colors are emitted depending on the
particular type of phosphor used in the bulb.
This is solid carbon dioxide, better known as
dry ice. It doesn't melt, it sublimes. Sublimation
is a solid to gas phase change, evaporation is a liquid to gas
change. (
source of the
image above).
The concentration of carbon dioxide in air is much smaller
than the other gases (it's about 0.04% but you don't need to
remember the actual value). That doesn't mean it isn't
important. We'll spend a lot of time this semester talking
about water vapor and also carbon dioxide. Water vapor and
carbon dioxide are the two best known and most important
greenhouse gases. The greenhouse effect warms the
earth. Concentrations of greenhouse gases such as carbon
dioxide are increasing and there is concern this will strengthen
the greenhouse effect and cause global warming. That's a
topic we'll look at during the semester.
If we were using a textbook we'd probably find something like
the following table near the beginning of the book ( I found this
table a few years ago in a Wikipedia
article about the earth's atmosphere ).
I like our list of the 5 most abundant gases better. It's
much more manageable. There is almost too much information
in a chart like this, you might be overwhelmed and not remember
much. Also unless you are familiar with the units on the
numbers they might be confusing. And notice you don't find
water vapor in 3rd or 4th position near the top of the
chart. That's because this is a list of the gases in dry
air. Unless you're very attentive, you might miss that fact
and might not see water vapor way which is included at the bottom
of the chart.
If you click on the link above to the Wikipedia article on the
earth's atmosphere, you'll find that the list above has been
replaced with a shorter simpler list (much more like the one we
created in class).
2. Dew point temperature
Water plays many important roles in the
atmosphere. One of them is the formation of clouds, storms,
and precipitation. Meteorologists are very interested in
knowing and keeping track of how much water vapor is in the
air. One of the variables they use is the dew point
temperature. The value of the dew point gives you an idea of
how much water vapor is actually in the air. A high dew
point value means a higher the water vapor concentration.
The chart below gives a rough equivalence between
dew point temperature and percentage concentration of water
vapor in the air.
Note that for every 20 F increase in dew
point temperature, the amount of water vapor in the air
roughly doubles.
Air temperature will always be equal to or warmer than the
dew point temperature. Experiencing 80o F dew points would be
very unpleasant and possibly life threatening because your
body might not be able to cool itself ( the air
temperature would probably be in the 90s or maybe even
warmer). You could get
heatstroke and die.
Click here
to see current dew point temperatures across the U.S. Here's
a
link concerning unusually high, even record setting dew
point temperatures.
