National Chemistry Week repost: elements.

Still swamped, but National Chemistry Week must go on. Here’s a post from the archives about one of the basic concepts of chemistry, what defines an element.

As far as chemists are concerned, the world is made up of atoms and various assemblies and modifications thereof. Those atoms and modifications of atoms are, in turn, made up of protons, neutrons, and electrons. Protons have a +1 charge and a mass of 1.0073 amu [1]. Neutrons have zero charge and a mass of 1.0087 amu. And electrons have a -1 charge and a mass of 5.49 x 10-4 amu. Various combinations of these three will give you atoms, radicals, and ions [2]. Protons and neutrons hang out together in the nucleus of your atom (or radical or ion), while electrons can be thought of as zipping around the nucleus [3].

An element is defined by the number of protons in the nucleus. The element oxygen has 8 protons in the nuclei of its atoms. Any atom (or radical or ion) that has exactly 8 protons is an oxygen atom, and all oxygen atoms (or radicals or ions) have exactly 8 protons. It doesn’t matter how many electrons there are zipping around the nucleus; that determines the net charge. It doesn’t matter how many neutrons there are in the nucleus; that determines the atomic mass (and which isotope of oxygen you have). The number of protons in the nucleus is all that counts when you’re determining the element you’re dealing with.

Lots of compounds (like water) are made up of more than one element (here, hydrogen atoms and oxygen atoms in a ratio of 2:1). Elements, however, have molecules that are made up of a single kind of atom — elemental hydrogen is H2, while elemental oxygen comes in two forms, O2 and O3 (ozone). Most textbooks will define an element as a substance that can’t be broken down into simpler substances. (This means that chemists must view protons, neutrons, and electrons not as substances, but as the building blocks from which substances are made.)
_____
[1] The abbreviations “amu” stands for atomic mass unit. 1 amu = 1.66056 x 10 -27 kg.

[2] Ions are nuclei (or multinuclear assemblies) where the total number of protons does not equal the total number of electrons — meaning they have a net-positive or net-negative charge. For example, Cl has one more electron zipping around the Cl nucleus than there are protons in that nucleus.

A radical is a nucleus (or a multinuclear assembly) with an unpaired electron that’s “looking for action” (i.e., is generally highly reactive). For example Cl. has the same number of protons and electrons (i.e., a neutral charge), but one of its 17 electrons is not paired, and thus the radical is “looking” for an opportunity to react with something else that will provide an electron to pair with.

Not to get too anthropomorphic or anything …

[3] Strictly speaking, you really shouldn’t think of electrons as having a well-defined location until you go looking for them with a “measurement event”. But as far as anyone can tell, they probably don’t stray too far from the positive charge concentrated in the nucleus.

National Chemistry Week repost: How does salt melt snails?

It should be noted that for some of us, nearly the whole world comes to us through the lens of chemistry, every week of the year. Here’s another post from the back-catalogue that brings my chemical sensibilities to the garden:

In light of our recent snail eradication project:

Why does salt “melt” snails and slugs? (And how do people manage to prepare escargot without ending up with a big pot of goo?)

To answer this question, let us consider the snail as seen by the chemist:

Snail1.jpg

Continue reading

National Chemistry Week repost: Periodic table of wow!

In honor of National Chemistry Week, another post from the archives:

I suspect I’m late to the party on this one, but I just had occasion to check out The Periodic Table of Videos produced at the University of Nottingham. It’s a collection of 118 short videos (ranging in length from approximately one to ten minutes each), one for each of the elements currently in the Periodic Table of the Elements.

I did not watch all 118 of them, but the ones that I did watch covered, among other things:

Continue reading

Holy mole-y, it’s National Chemistry Week!

Your humble blogger is swamped with work, but National Chemistry Week (October 17-23) waits for no overworked academic. So, let me offer a nugget from deep in the archives about why I dig chemistry.

What’s so great about chemistry? Of course, if you’re a kid, chemistry has the allure of magic — something might explode! (For those averse to permanent damage, there are plenty of cool chemistry activities that are much safer than whatever my brother did with his store-bought chemistry set to scorch the hell out of our parents’ card table.) But I suspect its real charm for students, at least when it’s taught right, is that it’s a science that looks for the “whys” pretty early in the game. In general, introductory chemistry doesn’t involve much memorization (whether of equations, as in physics, or of Linnaean taxonomy, cell organelles, phases of mitosis, or any of the other important details one has to remember in a biology class). Rather, you learn how to use the Periodic Table almost like a decoder ring to figure out why various substances behave the way they do. From the very beginning, the chemistry student is thinking not just in terms of facts, but in terms of rationalizing those facts. For every weird exception you learn to a regular pattern, the challenge is to understand why it breaks the pattern.

In this chemical universe the student enters, things start to make sense in a way that everyday life hardly ever does. It can be downright seductive. But of course, the orderly chemical universe to which the student is exposed is the product of much labor in laboratories. What happens in the labs can seem chaotic rather than orderly, and sometimes it is only the determination of the chemists to find the underlying order that keeps the going back to the bench to tame the chaos. Needless to say, finding the order in chaos can be seductive, too.

While chemistry often gets props for being a practical subject to pursue (where “practical” usually means leading to gainful employment, and the contrast class is something like philosophy), a lot of the people I know who went into chemistry were led by their hearts more than their heads. Chemistry just felt like the right way to engage with the world.

Primo Levi expressed this as well as anyone else has. Writing about his experiences as a chemistry student in Italy during the rise of Fascism on the eve of World War II, he said he felt

That the nobility of Man, acquired in a hundred centuries of trial and error, lay in making himself the conquerer of matter, and that I had enrolled in chemistry because I wanted to maintain faithful to that nobility. That conquering matter is to understand it, and understanding matter is necessary to understanding the universe and ourselves: and that therefore Mendeleev’s Periodic Table, which just during those weeks we were laboriously learning to unravel, was poetry, loftier and more solemn than all the poetry we had swallowed doen in liceo; and come to think of it, it even rhymed! …

[T]he chemistry and physics on which we fed, besides being in themselves nourishments vital in themselves, were the antidotes to Fascism … because they were clear and distinct and verifiable at every step, and not a tissue of lies and emptiness like the radio and newspapers

(The Periodic Table, pp. 45-46.)

Why does it choke me up to see Levi want to conquer matter by understanding it, or to see that his motivation to understand matter is a desire to understand the universe and himself? Coming at a science like this, you can see why a couple centuries ago it was called natural philosophy. As nuts and bolts as the work of a chemist can be — and Levi was for most of his career a chemist who took on problems in different industrial labs, including an IG-Farben lab while he was a prisoner at Auschwitz — the drive here is to understand the substance of reality, to get at knowledge we can be sure of and can hold in common with others. Wanting something like this — to understand of the universe we’re in and how we fit into it, to share our experience with our fellow human beings — feels like the most human of impulses. Science is not the show-offy acting out of the maladjusted braniac, but the labor of the human spirit.

Maybe if more of that got across to science students, and to the public at large, cultivating scientific literacy wouldn’t seem so much like taking a dose of castor oil.

Friday Sprog Blogging: the glorious return of the science fair!

At least, the Free-Ride offspring’s elementary school thinks it has money in the budget for a science fair this Spring. Sure, I know that grown-up science is frequently constrained by a rapidly changing funding landscape, but I’m not sure that including this element of scientific activity is what will catch a kid’s imagination.

Anyway, I asked the sprogs to jot down their current thoughts on what they might want to do for the science fair this year. Here’s what they gave me.

The elder Free-Ride offspring (now in sixth grade) hasn’t really latched on to one idea yet. The current list of options reads as follows (with my commentary in square brackets):

  • Which food does Snow like best? [We definitely need to read up on the rules about observational studies of domestic animals in science fairs. As well, this kernel of a project idea requires some careful thinking about controls.]
  • Snails or slugs: which are more efficient? [Efficient at what, wonders Dr. Free-Ride.]
  • Which is more viscous, honey or syrup? [I reckon we’d need a few more substances in the comparison. Plus some exploration of what it is about each substance that makes it more or less viscous.]
  • Trick people’s palates! [Intriguing! But also cryptic. Is this going to be about food chemistry, or tastebuds, or psychology?]
  • How heat affects bunny naps. [Again, we need to get right with the rules on animal observational studies. And we may be running out of really warm days to use as data points.]

The younger Free-Ride offspring (now in fourth grade) has been gravitating toward an idea inspired by a family camping trip at Lassen Volcanic National Park:

Working with sulfur.

Found in Sulfur Works, Bumpass Hell, & Devil’s Kitchen [all sites at Lassen].

What do you have to do to make sulfur smell like rotten eggs?

Can we find sulfur in foods we have in the house (besides eggs)? How could we get the sulfur out?

What happens if we put wet soil and trapped steam (don’t know how) in a bowl, then put sulfur soil (ground sulfur to a powder) on the top layer?

This could be really interesting … but I’m wondering now if our kitchen is going to need a fume hood.

Stay tuned.

Friday Sprog Blogging: Kids Day at SLAC 2010 and the saga of Mr. Marshmallow Man.

The younger Free-Ride offspring reports on one of the workshops at Kids Day @ SLAC 2010:

Dr. Free-Ride: Tell me the story with Mr. Marshmallow Man.

Mr. Marshmallow Man

Younger offspring: Mr. Marshmallow Man got put into a vacuum chamber, and it was also kind of like a time machine, ’cause when they put him in, he was, like, porking out on all these marshmallows. Except, he wasn’t eating himself. And then, the time flew fast and he turned eighty. Then he porked out some more. And then, time flew more fast, and then he turned a hundred, and then his head fell off and I came to his funeral. (In a dramatically sad voice) I’ll never forget you, Mr. Marshmallow Man!

Dr. Free-Ride: OK, but can you tell me what was happening in terms of the balloon in the vacuum? What actually happened?

Continue reading

Friday Sprog Blogging: Kids Day at SLAC 2010 hazards and mitigations.

Longtime friend of the Free-Rides LO has been instrumental in hooking the Free-Ride offspring up with Kids Day @ SLAC. Finally the year has come when the younger Free-Ride offspring meets the age requirements to join the elder Free-Ride offspring. As is our practice, we prepared by reviewing the safety information:

Dr. Free-Ride: So, we’re talking about Kids Day @ SLAC. I’m showing you the logo for this year’s Kids Day @ SLAC. There seems to be some sort of — I don’t know if that’s a laser beam or something. Looks interesting. But, the part we need to discuss has to do with the safety information. “All children must wear long pants, Kids Day T-shirts” — which you guys will get from LO and put on when you get there — “closed-toe shoes, no jewelry, and long hair must be pulled back. Please review the hazards and mitigation information on the workshops.” Younger offspring, let’s look at workshop B.

Continue reading

Friday Sprog Blogging: please stand by.

Dr. Free-Ride is pinned down in committee meetings for a while.

There will be a conversation with the Free-Ride offspring posted later today. In the meantime, here are whiteboard traces of a science-y conversation the sprogs had recently with Dr. Free-Ride’s better half.

On our whiteboard

Yeah, I find the “sand” thing worrisome, too.

Practical chemical engineering.

It’s day two of my training course, and as I contemplate my mug of decaf, I am suddenly flashing back to a question that was rumored to be part of the chemical engineering qualifying exam in my chemistry graduate program. As it’s an intriguing problem, I thought I’d share it here:

In the dead of winter, a professor sends his grad student out into the cold to fetch him a hot beverage from the cafe. “Coffee with two creams, and make sure it’s HOT when it gets to me!” the professor barks.

Shivering from fear as much as cold, the grad student procures a 12-ounce styrofoam cup of hot coffee and two little containers (maybe 20 mL each) of half and half at the cafe. To maximize the temperature of the coffee when it is delivered to the prof, should he add the half and half to the coffee before he walks it through the cold or after?

Feel free to work together on this problem, and please show your work in the comments.

Workplace safety: use your BRAAAINNS!!

I’ve just gotten back from a conference, and I was blaming the travel and time zones for the fact that I feel like this:

sbzombies_misc1.png

However, from the looks of things, it seems there is some kind of zombie epidemic on ScienceBlogs today. (I suppose this means I need to talk to the IT guys about internet security issues, if I got zombified through my browsing. Assuming they’re still taking help tickets from zombies. I wonder if being a zombie with tenure makes a difference …)
Anyway, in the meantime I thought it might be useful to break out the workplace safety talk for new students. While I can’t find the original filmstrip* to link to it, mine skews heavily towards what chemistry students need to know. However, you should feel free to shamble into the comments with that tasty brain of yours and add additional tips for safe conduct in your own field of study.

Continue reading