Help Me to Help You Learn
Please submit your questions, comments, and suggestions using the form at the bottom of any page in the course website. All of the forms are really the same one, so wherever you are at our site, if a question occurs to you, send it along. I will try either to incorporate your question into class material or answer it directly in class.
Student contributions appear here in most-recent-first order. Names of contributors will not be included UNLESS you tell me specifically in your message to show your name with your contribution.
If I have time, I will respond briefly -- in italics, like this -- to your questions, or mention when or in what context we might treat them in class.
(NOTE: My web editor sometimes changes font sizes willy-nilly, so I often "select all" and reset the font sizes to make them all the same. But if I do that on this page, I will lose all the subscripts [as in CO2)] that I tediously wrote. So it's easier just to leave the variable size fonts.)
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February 15:
I do not understand the first law of thermodynamics and how it relates the law of conservation of energy. Can you explain.
There is really nothing to explain. The first law IS the law of conservation of energy.
From Wikipedia:
The law of conservation of energy states that the total energy of any isolated system (for which energy and matter transfer through the system boundary are not possible) is constant; energy can be transformed from one form to another, but can be neither created nor destroyed.
Remember what a law is:
From "What is Science" at One Culture:
I am not saying that a law is a pattern that nature must obey. I am saying that a law is a pattern that, when we judge by the data, nature appears to obey. Stating a law is much like asking whether nature always does things in the manner we have noticed. If so, that is useful information. (http://oneculture-reflections.blogspot.com).
February 11:
Reality check please. As I understand it, elements (Na & Cl) are different than compounds (NaCl) because the former can't be taken apart, or otherwise messed with and the latter can be both put together and taken apart. But, if the elements were put together from H and He by stars, with enough energy they should be able to be taken apart. Or am I missing something? Is this a more difficult, but similar situation to nuclear fission of heavier, more unstable elements? Or not? Would E=MC^2 be involved in both cases?
In stars, elements can fuse to form larger elements, and in nuclear reactors, elements can undergo fission into smaller elements. But the energies needed to start fission are enormous compared to the energies needed to start chemical processes. Fission is a nuclear process, sometimes mis-named "nuclear chemistry", but it's not chemistry at all. It entails breaking nuclei, while real chemistry entails breaking only the much weaker chemical bonds that involve electrons, not nuclei.
February 9:
Is it true that matter is never destroyed? It just gets turned into another form?
It's safer to say that matter and energy are never destroyed. Both can change forms (mechanical energy to electrical energy in hydroelectric power generation, two gaseous chemicals reacting to form a solid (ammonia gas and HCl gas combining to form a "snow" of ammonium chloride crystals). In addition, matter and energy are interconvertible (nuclear energy entails conversion of the mass of a fuel to heat energy). But in all processes we know of, the total of mass and energy of the starting materials is the same as the total mass and energy of the products. In most common chemical reactions, the conversion of mass into energy is so tiny that it appears that mass itself is conserved. But for example, if the chemical reaction gives off heat, an undetectably small amount of mass becomes energy.
February 8:
Can it be said that Chemistry is the "heart and soul" of Physics?
Not in the same sense as I said that structure-function relationships are the heart and soul of chemistry. What I meant is that there relationships are the gold that chemists are trying to mine in order to understand matter, which is their overall subject. Chemistry is not central to physics; it is one area of applications of physics, an also an area of applications of mathematics. Chemistry is sometimes called the "central science" because of its many areas of application, including biology and geology.
Heat and pressure affect the volume of a gas. What about a current of electricity?
A gas is a poor conductor of electricity, but if the voltage is high enough, atoms or molecules of gas can pass electricity between two electrodes. The result will be emission of light at the wavelengths characteristic of the gaseous substance. The gas will be heated as a result, which would increase the pressure, but this would have to be done in a glass tube, so volume would not change.
Carbon is in group 14 of the periodic table. It has 4 electrons in it outer shell and is highly reactive. Below C in group 14 is Silicon. It does not seem to be as reactive as C. Why?
Hard to answer in brief. C is far more versatile in forming molecules, but both C and Si are very stable at room temperature and require heat or reactive chemicals to be drawn into combining with other elements (unlike Na, which reacts violently with water or moisture in the air with no heating needed). Si forms boring network solids, such as silicon dioxide, which resist further reaction. C can bond to itself and other 2nd-row elements (through single, double, and triple bonds), so it forms a myriad of compounds. The number of outer-shell electrons tells you something about how electron sharing might happen, but little about relative reactivity. Depends a lot on what they are reacting with.
February 7:
Q: How do you tell the difference between a chemist and a plumber?
A: Ask them to pronounce "unionized".
January 26:
Free app for Android (and probably iPhone) app for following the sky. The screen shot was from the beginning of the class showing Venus in the SE.
SkySafari is available for Android phones at Google Play and for iPhone at the Apple App Store. The free versions are enough to get you started learning your way around the sky, and to see you need any additional features.
January 25: In the example of combining hydrogen and oxygen from the atomic weights, I understand the ratio of 4 to 32, but you extend the ratio to 4:32:36.
Why the third number 36?
I edited that passage a bit to mention also the mass of the water produced (36), and I hope that makes it clearer. The ration 4:32:36 is the ratio of masses of the one H2 molecule (2): 2 O2 molecules (32); and 2 H2O molecules (36). Note that mass is conserved in all chemical reactions: 4+32=36.
January 22: There is a saying- Red sky at night, sailors delight; red sky at morn, sailors take warn. Which in my limited experience sailing tended to be true. Why does this same color predict such different outcomes at the different times?
Read this page. Especially note the short paragraphs that follow each of the two red-sky pictures at the end of the article.
January 20: This is a silly point but since my favorite number is shared by Hank of Crash Course I wonder why you don't use it when talking about moles, etc. Plus, your million billion billion is 10^24 which is not quite right, of course.
Anyway, here is 6.022 x 10^23.
Yes! The mole (official unit name is mol) is roughly 6 followed by 23 zeros, which is about 40% less than a million billion billion (the number 1 followed by 24 zeros). For our purposes, that's close enough, and a bit easier to say (and maybe a little easier to imagine) than 6.022 x 10^23. Point taken. Perhaps I am thinking too much about the students who have had practically no education in chemistry or even science, and need to make sure I make better connections with those who have had a little or a lot.
January 18: I don’t know where—or even if—this will fit in this OLLI chemistry course, but… I’d like to understand “handedness.” I understand that handedness relates to how a crystal deflects polarized light, but why are some crystals “levo” and others “dextro”? Do all crystals have both a levo and a dextro form? If not, what determines which form a crystal takes? And I gather one form can be more pharmacologically effective than its “twin.”
For 30+ years I have been taking levothyroxine (have never heard that there is a dextrothyroxine). I don’t know if levothyroxine’s handedness governs its ability to get where it must go in my body, or allows it to “dock” with some cell in my body to achieve proper thyroid function. Do considerations of handedness occur elsewhere in chemistry? If this is too big a “bite" for this course, can you recommend any reasonably clear reading for a layman who last studied chemistry 64 years ago?
Later in the course, we'll discuss the handedness of molecules. Look for the short story "Technical Error", by Arthur C. Clarke
January 18: Perhaps you share information some time about the chemistry of rapid Covid tests and how they are chemically different from or similar to that of pregnancy tests.
I plan to introduce you to some of the methods that make up these kinds of tests. They are quite complex tests, but some of the underlying works of them are pretty simple.
Here is a video explanation of what's going on in the "rapid" or "lateral flow" COVID-19 test.
January 18: Once again, I don't really understand that poem!!
We'll talk about it.
January 18: A 'background' question. While looking at this page, on the edges of the page, I see magnified grains ? of ? is it salt or??
I like the pun. I have no information about the page background. Probably it is a salt, but there are many salts. Does not look very pure if it's a colorless salt like sodium chloride (table salt). Question: If Himalayan is so all-fired pure, why is it pink? Pure table salt is colorless, so there must be some impurity there.
January 18: What was the cloud chamber (trying?) to show us and why?
We will examine those mysterious tracks very carefully.
January 17: Feeling overwhelmed...I am guessing (hoping??) that the nature of the beast is that we have to know about all these little bits, "at once" until they can begin to make sense "together?"
I hope some pieces will begin to fit together right away.
January 17: At some point I would be interested in talking about how heat pumps work, if that is appropriate for this course.
Very appropriate for later in the course. Will do.
January 16: Is there a chemical explanation for the formation of the ice disc that has formed in the Presumpscot River in Westbrook?
January 16: Curiosity question from class 1-You showed a picture of snow flakes on your deck. The snow flake crystals appeared to be in clumps with bare spaces between rather than homogenously spread. Is there some physical force at play to explain that distribution?
Randomness. It had just begun snowing, and not for long enough to cover the surface.
January 16: Gale: recognize that people come to this class with varying backgrounds. Mine is at "zero." I struggle with anything beyond atoms (your 4 versions of portraying these helps a lot--I am a visual learner first and foremost.), so when people ask about isotopes I am really lost!
Just be calm. We have only met for two hours. If you were already comfortable with your command of chemistry after two hours, that would be some kind of miracle. We'll start building things more systematically at Class #2.
And you might learn something useful from this video, "The Biggest Myth in Education".
Student Contributions Before Class #1
January 11: The periodic table is very old. In the new world with discovery of small particles, sub-particles and variations in particles, are there new half elements or sort-of elements that would fit between the main elements on the periodic table?
In a word, no. Hope you'll see why as the course progresses.
January 9: Is there a reason why the periodic table is organized the way it is?
Oh, yes, and good theoretical models of atomic behavior to suggest that the standard organization fits reality well.
January 6: What are some other ways by which we could format the periodic table?
Not many, without losing the sense it makes.
January 5: The Xenon haiku is pretty straightforward IF you are reading "The Hail Mary Project" by Andy Weir. He is gobsmacked to find that the aliens he encounters near Tau Ceti make their ship out of a metal compound of Xenon. Here is one of Brady's videos about Xenon with Prof. Poliakoff: https://youtu.be/M71wqjf4SuE
Andy Weir is pretty great credible sciFi author.
Poliakoff refers to xenon reacting with metals. Fluorine is not a metal. And a metal compound of xenon would not be metallic. To my knowledge, all known xenon compounds are gases, which are not so great as building materials.
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