Friday, March 30, 2007

Why (high school) Chemistry Rots









Why do I despise high school chemistry? Because it's described in the antiquated terms of early 20th century science.

I'm talking about you, Avogadro constant.

I was tutoring my son this week when I came to a realization - we don't need the Avogadro constant anymore.

It was useful before the existence of the atoms and molecules were established. But in 2007, we know about matter at the atomic and molecular scale, so we should stop replacing the concrete picture of subatomic particles, atoms and molecules with the (in)convenient ideas implied when we talk about moles of material.

The Avogadro constant is really just a bad approximation of one divided by the mass of the proton. It's a bad approximation because instead of using the actual mass of the proton to calculate the constant, the accepted value is one twelfth the mass of a carbon 12 atom. The error comes about for several reasons. For one thing, there are twelve particles in the nucleus of carbon 12, but only half are protons, the other half are neutrons (which are heavier than protons, leading to a small over estimate). There are also six electrons floating around a normal (that is, neutral) carbon 12 atom, leading to another error from over estimating.

All of these things stick together to form one atom, which leads to yet another error. The binding energy that holds atoms together reduces the mass of carbon 12 by a lot more than the added mass of heavier neutrons and the extra electrons.

Put all these things together, and one divided by Avogadro's number is nearly equal to the mass of a proton in grams. How annoying is that?

Why do I hate the Avogadro constant? Well kids, I have loads of reasons. But here's three.

-- If we use proton mass in chemistry calculations instead of the Avogadro constant, then you could lighten your load of constants that you need to know by one at least. Sure, I'll have to memorize or look up the mass of the proton now, but I have to look that up on occasion anyway. I hate memorizing stuff, so this is a big deal to me. As a bonus, you can forget about the ideal gas constant (R) too. We only had to make that one up to atone for inventing the Avogadro constant in the first place.

-- Instead of struggling to remember the abstraction of moles, we could just think of the actual constituents of molecules in balancing chemical equations, leading to a more clear understanding of what's going on in chemistry. For example, Wikipedia says 'A mole is much like "a dozen" in that both units can describe any set of elementary objects . . .' In other words, using the Avogadro constant in chemistry makes as much sense as going to Dunkin Donuts a and asking for a twelfth of a dozen donuts when you only want to buy one, or one and a twelfth dozen when you want 13 (which can also be written 1.0833333333 dozen donuts).

-- The ideal gas law would make a lot more sense. What we're really talking about in the ideal gas law is particles bouncing off of the walls of a container, so PV=nRT is really PV=NkT, where 'N' is the number of particles in the container, and 'n' is the number of 6.0221415x10^23 sized batches of particles in the container. 'N' is much more sensible than 'n', and takes a LOT less oxygen to describe.

My boss argued with the third point by essentially paraphrasing this Wikipedia entry about rationale behind moles -

Moles are useful in chemical calculations, because they enable the calculation of yields and other values when dealing with particles of different mass.

Number of particles is a more useful unit in chemistry than mass or weight, because reactions take place between atoms (for example, two hydrogen atoms and one oxygen atom make one molecule of water) that have very different weights (one oxygen atom weighs almost 16 times as much as a hydrogen atom). However, the raw numbers of atoms in a reaction are not convenient, because they are very large; for example, just one mL of water contains over 3×10^22 (or 30,000,000,000,000,000,000,000) molecules.


I don't get it, why would chemists be upset by 3×10^22 (or 30,000,000,000,000,000,000,000), when a number approximately equal to 6.022^23 (or 602,200,000,000,000,000,000,000) is not a problem? Just round to three significant digits and use exponential notation, for crying out load.

In fact, using moles actually forces us to talk about the number of a number of particles. I'd rather just talk about the number of particles.

Here's the bottom line: all you chemists using the Avogadro constant, hitch up your belts and move along from the science of the early 1900's to the science of the late 1910's and beyond by ditching that crazy constant.

Then, perhaps, students can start learning about chemistry as it happens for real.

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Wednesday, March 28, 2007

The Look of Science

I’m sitting in an the Chicago airport right now waiting for a connecting flight to St. Louis - home of the National Science Teacher’s Association national meeting this year (of course this won’t be posted until I’m cozy in my hotel and have wireless). Anyway, my colleague just nudged me and pointed out how easy it is to tell who else is headed to this conference. Science teachers tend to have a certain look - or more accurately one of a few types of looks...

I wonder, do most groups have a characteristic look? I mean, if I were more attuned to the music culture would I be able to pick out fellow travels heading toward [insert name of big music fest here]? Or the nurses or architects headed toward their respective meetings?

It’s interesting to think about how we surround ourselves with people that resemble us. Or maybe it’s that we change ourselves to resemble the people that surround us. Or maybe our careers AND our looks both reflect our values.

I know scientists have studied how people judge the attractiveness of others and found that people tend to find attractive the people that look like themselves or like those they grew up with. Maybe when we see people that resemble us (or those we grew up around) being successful in a particular type of career that makes us more confident/comfortable in those areas.

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Tuesday, March 27, 2007

Expanding prices even more

Anyone that drives anywhere is familiar with paying MORE for gas in the summer. I learned last night that most of us are paying MORE than MORE in the summer, thanks to physics (and lack of regulations in the gasoline industry).

This week I've been experimenting with homemade thermometers. To make one you fill a bottle with room temperature water, add a few drops of dark food coloring and a straw, and seal the straw in place with some clay. The water level in the straw will change in proportion to the temperature of the thermometer's surroundings.

Heat is related to the motion of atoms. The molecules in warm water move faster than those in cold water. This increased motion causes warm water to expand, thereby raising the water level in the straw.

What does this have to do with gas prices???

Well, as Jamie Court pointed out in American Public Media's Marketplace, gas pumps charge us by the gallon, which is a unit of volume. And gas, like water, expands when it gets warm.

Gas companies account for temperature-induced changes in volume when they buy gas from oil companies, but they don't account for it when they sell it to us (except in Hawaii).

This means that a gallon of gas in the summer has less energy than a gallon during a colder time of year. In warmer areas, he figures, people pay on average 3 centers more than the advertised price of a gallon for a standard gallon's worth of energy. This overcharging costs Americans about $1.7 billion every year.

Of course you get the good end of the deal if you live in a colder climate. Unless you live in Canada, where they temperature-regulate gas pumps.

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Friday, March 23, 2007

Pretty Physics Picture of the Week


This is an optomechanical resonator, which basically means that the oscillations from light that the structure absorbs can cause it to vibrate. According the authors of the article, Tal Carmon and Kerry J. Vahala of the California Institute of Technology, published in Physical Review Letters, the color bands represent distortion of a micrometre-sized silica sphere mounted at the top of a tiny pillar.

I haven't found anything in the paper to say what the oscillating sphere might be used for, but tiny oscillators are important for all kinds of devices, including the CPU at the heart of your PC, communication systems, and measuring instruments. But I'm only posting this today because it looks cool.
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Thursday, March 22, 2007

Laces Optional

So I'm at the gym last night (don't act so surprised. I go on occasion...) flipping through the channels on the mini-TV attached to the treadmill. I stop on CSI Bones. It was Bones. Anyway, I'm half paying attention when I hear one of the characters say physicist. It takes me a moment to process the context-

Character 1 is commenting on Character 2's bad taste in men and backs up his point by listing her previous boyfriends: the man who cut off his brother's head, the cult recruiter, and the physicist who couldn't tie his own shoes.

Nice.

(10 pts to anyone that can explain to me why the one ex cut off his brother's head...)
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Tuesday, March 20, 2007

A Nickel for your Thoughts

Waste has been used by creative minds around the country to produce unique works of art, foundations for golf courses, fuel for buses, and countless other wonders. So, to all of you creative minds I challenge this - find a good use for 15,300 tons of nickel.

The U.S. Department of Energy is seeking input from industry representatives on the safe disposition of approximately 15,300 tons of nickel scrap recovered from uranium enrichment process equipment...(press release)

Okay, maybe we should leave that one to the experts. But talking about uranium enrichment and putting waste to good(?) use reminds me of a story.

In Obsessive Genius, author Barbara Goldsmith talks about the early days of radiation treatment when radium bromide was inserted directly into tissue with needles or in small pellets. Eventually a gold filter was added, making the treatment more viable. She tells this story:

Instead of disposing of the gold filter after each use as instructed, one laboratory worker took the gold and forged it into a wedding ring for his fiance.

Eventually she had to have her ring finger amputated.

I hope he bought her a very big diamond after that.
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Thursday, March 15, 2007

Kewl Physics Cartoon

I love this cartoon. Click the image to see the rest of the panels.

But beware, if you're confused about centripetal and centrifugal forces, this isn't going to make it much clearer. On the other hand, once you come to terms with fictional forces arising from certain coordinate transformations, you'll laugh your head off.

I think I got up on the ultra-nerdy side of the bed today.
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Wednesday, March 14, 2007

Happy Birthday Albert!

I want to add my bit to the remembrance of Einstein's Birthday. To celebrate, here's my favorite Einstein joke:

Albert's standup routine
"I just flew in from outer space,
and, boy, are my arms shorter!"
bah-dum-dum-ching
I'm here all week, folks.
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Happy Pi Day and Happy Birthday to Einstein

March 14 is Pi day (3.14), as I'm sure you all know. And 1:59 is the most Pi minute of Pi day (3.14159). And, of course the 27th second of the 59th minute of the first hour (and 13th hour in the typical US time convention) is the most Pi second (3.1415927) of Pi day.

In celebration of the occassion, here's the Pi joke I used to torment my son when he first started learning about geometry.

"Pi r squared? That's crazy, Pi r round, crackers r squared!"

But even more importantly, it's Albert Einstein's 128th birthday. Here's a poem I wrote last year in honor of the greatest physicist of the modern age.

Young Albert E. and the Miracle Year
By James Riordon

Listen my friends, and shortly you'll hear
Why 1905 was a miracle year
For that was the time that a young patent clerk
By the name Albert Einstein did incredible work.

Now this is a story that comes in three parts
And the beginning, of course, is the best place to start.
But how it begins, I confess I don't know
So I made up a lie, and here's how it goes.

One day Al was walking and stopped to look down
At a puddle that spread in his way on the ground
As he studied the muck and the mud, Albert found
That his mind wandered back to the motion of Brown.

A small bit of dust or pollen or fluff
Would dance in the water, if 'twas tiny enough.
Some thought that the motions were signs of life
But old Reverend Brown had proved that's not right.

"The way the dust jiggles and wiggles and writhes,"
Al said, "it's no wonder some think it's alive."
He sat and he pondered and grasped for some notion,
What could possibly lead to this Brownian motion?

Well, he thought and he thought and he thought a bit more,
He thought 'til the thoughts made his thinking parts sore.
And with a little statistics and persistence galore,
He thought of an answer not thought of before.

"It's molecules," cried Albert, "too small to see
That are bumping the bits, that's what it must be.
And if water has molecules then so has that tree
And this rock and that bird, and yes, you and me!"

Well molecules and atoms at last were confirmed,
And solid state texts were rewritten or burned.
'Twas a wondrous discovery, though not without peer,
And it's hardly enough for a miracle year.

Now photons, like atoms, were once speculation,
Since light comes in waves with well known undulations.
But when light fell on metals and started a current,
Though the theories were clear, the experiments weren't.

Turn up the brightness and more electrons emerge,
While it's the color of light makes their energy surge.
How could this be? Albert knew it was wrong
If light was a wave as we'd thought all along.

He thought and he thought and he thought a bit more,
He thought 'til the thoughts made his thinking parts sore.
With a little deduction and persistence galore,
He thought of an answer not thought of before.

Light is sometimes a wave, that much is true,
But at other times it's a particle too.
And the same goes for atoms and marbles and pigs-
It just hard to tell when things get too big.

'Twas a wondrous discovery, and now he was near.
Yes, it's almost enough for a miracle year.

One day he was dreaming and thought if he might
Travel as fast as his photons of light.
What strange things would happen, what wonders there'd be
If he could approach the speed of light: c.

He thought and he thought and he thought a bit more,
He thought 'til the thoughts made his thinking parts sore.

With a little deduction and persistence galore,
He thought of an answer, not thought of before.

Now light speed is constant, experiment showed,
If you move quickly or move very slow.
But if light speed is constant, it's time that must change.
The answer's the answer no matter how strange.

This one little notion, while modest enough,
Led to a whole bunch of powerful stuff.
From time dilation to lengths that contract
To the source of the sunshine and cloud chamber tracks.

And perhaps Al's most famous discovery of all
Is the simple equation that most folks recall.
E=mc^2 made the fact plain
That energy and matter are one and the same.

And now there you have it, the case is quite clear
Why 1905 was a miracle year.
For in five famous papers and less than twelve months
Einstein came up with some fabulous stuff.

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Monday, March 12, 2007

Meeting Moments

Hopefully you've were able to keep up with us last week over at the Physics Meetings blog, there's some good stuff there - singing physicists, a big blue bear, the latest in quantum computing, and more.

Here are some of my favorite moments from the APS March Meeting:

"Ring of Fire"...well almost

From the physics sing-a-long


Why YOU should wear a bike helmet

From "Thursday Night Football Physics with Tim Gay"


How do you get a lead brick through airport security?

From "Thursday Night Football Physics with Tim Gay"


Want more? Visit the Physics Meetings blog!

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Monday, March 05, 2007

Physics Conference Blogging


We're all in Denver this week at the largest physics meeting of the year - the American Physical Society's March meeting.

Why is it called the APS March meeting? To distinguish it from the APS April meeting, which takes places in April (except the year that the April meeting took place in May and the year the March meeting took place in February). I keep telling them that they need a better name.

SpaceKendra, PhysicsBabe, and I ( Buzz Skyline) will primarily be posting over at our meeting blog - PhysicsMeetings.blogspot.com.

Although the names of the meetings don't tell you much, the March and April meetings cover very different topics.

The March meeting is chock full of materials science, nanotech, semiconductors, energy and biophysics (just to scratch the surface of the 7000 presentations here).

The April meeting includes more astrophysics, gravitational waves, and particle physics.

Drop by PhysicsMeetings.blogspot.com, and we'll let you know what fun and exciting stuff we're up to.
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Friday, March 02, 2007

That's amore

At the end of the day on Saturday, go outside and face east. Then throw your coat in the trash and get into the fountain. Okay, just kidding about those last two instructions. Seriously though, if you are on the eastern side of the US (or in various parts of Europe, Africa, and Asia) go outside just before sunset and look east.

As the sun sets and the moon rises there will be a total lunar eclipse - meaning that the moon will move through the Earth's shadow.

What will this look like to us? Well, if the moon is in the Earth's shadow then light from the sun won't be able to reach the moon. The moon doesn't generate any light of its own; it glows at night because it is reflecting sunlight. If sunlight doesn't reach the moon it will look black.

But there is a catch. As light from the sun travels through the Earth's atmosphere it scatters. Some of this scattered light will reach the moon even during a total lunar eclipse. This light will be mostly red and orange (for the same reason the sky is blue) and so the moon will have a reddish glow during the eclipse.

If that's not a good enough reason to go outside and look east, I don't know what is.

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Thursday, March 01, 2007

Rock the vote

I just read about the Seven Wonders of Illinois contest at Cosmic Variance and I have to add a plug for Fermilab. (Take it from an IL native, Fermilab is one of our seven wonders!) Go to the seven wonders site today - March 1 - and nominate the lab...it only takes a couple of minutes and you don't have to be an Illinois resident. Today is your last chance!
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