Chemistry Is The Central Science

(Xenos/9553) Theoretically no difference, in practice condensed water will be...

Xenos@rss.iscabbs.com — Sat, 11 Feb 2012 09:57:00 -0600

Theoretically no difference, in practice condensed water will be completely
pure H2O (assuming you're condensing into a clean container), whereas ice is
unlikely to be completely pure, so melted water will have other substances
dissolved in it.

(Swinia/9552) That reminds me of a question I wonder about ... so the blue col...

Swinia@rss.iscabbs.com — Fri, 10 Feb 2012 08:02:00 -0600


That reminds me of a question I wonder about ... so the blue color of glaciers
is caused by the reduction of dissolved gas within the ice under
compression...what's the relative dissolved gas content of glacial ice vs.
"normal" ice at ATP?

(Lochner/9551) At the moment of condensation and/or melting, the kinetic energy...

Lochner@rss.iscabbs.com — Mon, 06 Feb 2012 06:50:00 -0600


At the moment of condensation and/or melting, the kinetic energy of the water
molecules would be difference, which in turn could affect their propensity to
react with other substances.  The condensed water should be at a higher
temperature and thus more prone to reaction than the melted ice.

Beyond that... I dunno.

(Vlad Tepes/9550) is there a structural or other difference between water condense...

Vlad Tepes@rss.iscabbs.com — Mon, 06 Feb 2012 05:28:00 -0600

is there a structural or other difference between water condensed from vapour
and water thawed from ice?

(Lochner/9549) Yeah I figured it out. The salt disassociates into Na and Cl io...

Lochner@rss.iscabbs.com — Thu, 02 Feb 2012 16:59:00 -0600


Yeah I figured it out.  The salt disassociates into Na and Cl ions, resulting
in twice as many moles of material as sugar, which doesn't disassociate.

(DrSteve/9548) Except addition of sugar does next to nothing to adjust the fp o...

DrSteve@rss.iscabbs.com — Thu, 02 Feb 2012 16:32:00 -0600

Except addition of sugar does next to nothing to adjust the fp or mp of
water...ionic salts on the other hand...

(Xenos/9547) Your logic seems sound to me :-)

Xenos@rss.iscabbs.com — Fri, 27 Jan 2012 12:14:00 -0600

Your logic seems sound to me :-)

(Lochner/9546) Sanity check.

Lochner@rss.iscabbs.com — Fri, 27 Jan 2012 06:40:00 -0600


Sanity check.

Freezing point is a colligative property, meaning that it's affected only by
the number of solute particles, not the type.

In other words, if I add 100 NaCl particles to water, and I add 100 sugar
molecules to water, the change in freezing point will be the same for both.

However, if I add 100 grams of NaCl versus 100 grams of sugar, it'll be
difference between sugar is heavier and 100 grams of NaCl contains more
particles than 100 grams of sugar.

So, if I'm told that two solutions both have a concentration of 0.10 molaliy
(0.1 moles of solute per gram of water), that means both solutions contain the
same number of solute particles (one-tenth of a mole) and thus will change
freezing point the same amount.

(Xenos/9544) I don't but if you find one, please post it :-) I started record...

Xenos@rss.iscabbs.com — Thu, 05 Jan 2012 09:54:00 -0600

I don't but if you find one, please post it :-) I started recording a few a
couple of years ago for my students, but I ran out of steam. The University of
Nottingham has the Periodic Table of Videos (just Google). They're videos, but
you could probably just listen to them and get most of the key ideas. Oh also
if you want a nice readable book for general background, try The Disappearing
Spoon. It's available as an eBook so you can carry it about.

(Lochner/9543) For reasons that aren't important, I need to take General Chemis...

Lochner@rss.iscabbs.com — Wed, 04 Jan 2012 10:19:00 -0600


For reasons that aren't important, I need to take General Chemistry II.  I took
General Chemistry I in 1994 as an 18 year old, and I got a C in it.  I
understood it just fine, I just didn't study.  Frankly, I don't remember any of
it.

I've got about 10 days before Chem II begins and the best time for me to brush
up on Chem I concepts is during my commute, which is a total of anywhere from
90 minutes to two hours per day.

Can anybody recommend a podcast, audiobook, or other audio material which would
be appropriate to refresh my memory on this stuff?

(Xenos/9542) Question: Explain what is meant by the term 'salt'.

Xenos@rss.iscabbs.com — Tue, 25 Oct 2011 13:05:00 -0500

Question: Explain what is meant by the term 'salt'.
Student answer: A substance that is a base.

I give up.

(Xenos/9541) It has :-) The trouble is that you need to mix stuff with the c...

Xenos@rss.iscabbs.com — Mon, 29 Aug 2011 09:07:00 -0500

It has :-)  The trouble is that you need to mix stuff with the cat urine, and
getting to the source of the smell, if it's soaked into fabrics and you can't
wash said fabrics (e.g. because it's a mattress), is virtually impossible.
That said, alowing a concentrated solution of sodium bicarbonate to soak into
the affected area will probably catch the worst of it.

(Vlad Tepes/9540) with all the technology available, how come chemistry hasn't com...

Vlad Tepes@rss.iscabbs.com — Wed, 17 Aug 2011 21:30:00 -0500

with all the technology available, how come chemistry hasn't come up with an
effective treatment for neutralising cat odour?

(Mama K/9539) Wrong company, DrSteve.

Mama K@rss.iscabbs.com — Sat, 13 Aug 2011 04:42:00 -0500

Wrong company, DrSteve.

Got word that the company purchases cultured human skin cells on which to do
the in vitro testing.  (Can't remember if I posted that or not, and had already
started typing when I realized I couldn't remember.)  Hopefully this will stop
the cries of "but where are the embryos coming from?!?!?"

(DrSteve/9538) Mama K - I am going to go out on a limb and say the company you ...

DrSteve@rss.iscabbs.com — Fri, 12 Aug 2011 18:48:00 -0500

Mama K - I am going to go out on a limb and say the company you sell for is
Avon, they were the first of all the cosmetic companies to cease any animal
testing.  Not only does this mean live animals, it also meant dead animals and
even sausage casing was not allowed (often used in the industry to measure
"penetration" of various products).  Avon uses either human cadaver materials
or gene arrays.  They do however, have humans test their products after a lot
of review work.  Of course the labr ats fairly often mix stuff up and try it
unofficially anyway.
How do I know?  I used to work at their global R&D site in NY in New Technology
- Physical Sciences...our partner group was "biological" ie. skin science.

(Mama K/9537) For those of y'all playing along at home, here's the latest emai...

Mama K@rss.iscabbs.com — Mon, 08 Aug 2011 18:24:00 -0500

For those of y'all playing along at home, here's the latest email from the
Sales Director:

"Hi ladies! Here's the last of the info that should give you sufficient info to
answer the questions your customers may have regarding in vitro testing on some
of the ingredients in our new nighttime complex.

Manufactured skin cells that the company actually purchases is what the
ingredients are tested on in a glass or plastic test tubes. And that's it : )
They do this rather than testing on panelists."

Which is what I told her via email 5 days ago.

(Aztech/9536) If I had to guess, it's an issue of air/propane mixture where th...

Aztech@rss.iscabbs.com — Mon, 08 Aug 2011 18:13:00 -0500

If I had to guess, it's an issue of air/propane mixture where the propane is
hot enough to ignite.

If you've turned on the burner (and their sparker, or whatever causes ignition)
before you have a buildup of gas, it probably burns the gas as soon as it
shoots out.  This may not have the optimal burn ratio.

But if you turn on the gas first, by the time you hit the burner switch,
there's some gas built up, which has had a chance to mix with air, and you get
a good burn.


Think about it like turning the wick up or down on a kerosene lamp:  if you
turn it too low, the vaporizing kerosene isn't mixing well with the air before
igniting, so you get a tiny flame.  Turning the wick up, you get more vaporized
kerosene (well, lamp oil), and a bigger flame.

Though, remember, air/fuel ratios can go too high and too low:  without any
air, fuel won't burn.  Without any fuel, air won't burn.  And if you're not in
a sweet spot, you'll get a lot of smoke b/c of inefficient burning (well, with
a lamp...not sure what that parallel would be for a propane grill).

(Kena/9535) Okay, so, really, this is more a chemical engineering question t...

Kena@rss.iscabbs.com — Mon, 08 Aug 2011 17:36:00 -0500

Okay, so, really, this is more a chemical engineering question than a chemistRY
question, but this is the lucky forum to receive my question, regardless.  I've
got a grill -- propane.  Got the spiffy little propane bottle off to the side.
The same kind of grill you see a zillion of at Sears or Home Depot or wherever.
If you do it the way you're supposed to, everything works fine:
- All dials set to "off."
- Turn on propane tank.
- Turn on burners.

If, however, I goof (as I did when I originally got the stove), and do this:
- All dials set to "off."
- Turn on burner(s).
- Turn on propane.
Well, then, it sucks.  Like, is barely even on.  I did this again for the first
time in a couple of years yesterday -- same problem.

What in the Hell is the difference between the two?

(Mama K/9534) Just received an email from the Sales Director.....editing sligh...

Mama K@rss.iscabbs.com — Fri, 05 Aug 2011 12:01:00 -0500

Just received an email from the Sales Director.....editing slightly to remove
company name.

"To those of you on the call Wed night, just wanted you to know that, per your
questions and the discussion we had ref: the "In Vitro testing" comment about
our newest Timewise Nighttime product, I did call (Company) Medical Relations.
Her answer was simply this: The product was tested on "isolated skin cells from
live human beings."  I then asked her wehere these skin cells came from, like
people just volunteer to donate their skin or something?? She didn't know how
to answer that so she forwarded my question to the research dept. They will
call me back within 24-48 business hours.

Ladies, I know with all of my heart that (Company) would never do anything
harmful or immoral, I do understand, however, that we need to have a clear
answer in our minds to our questions so that we can give clear answers to our
very educated customers: )
"

*sighs*

(Mama K/9533) Aztech> You nailed it. "...activates collagen production....co...

Mama K@rss.iscabbs.com — Fri, 05 Aug 2011 10:09:00 -0500

Aztech>  You nailed it.  "...activates collagen production....controlling the
activity of damage signals in the skin....targets the skin matrix.....restores
the skin barrier.....quiet the message signals so less damage gets through to
cells in the first place..."  Other ingredients included in the benefits claims
are pomegranate sterol, chestnut seed extract, cotton seed extract, and acai
berry extract.  The last two, plus the palmitoyl tetrapeptide-7, are included
in the fighting free radicals section.

I talked to the Sales Director last night, and asked if she'd recieved the
email I sent her.  She said she had, but 1) didn't understand any of it, and 2)
wanted the exact language used by the company for whom we sell to explain it to
others.

(Aztech/9532) I'd think the Ames test results ("Hey, it won't mutate you or di...

Aztech@rss.iscabbs.com — Thu, 04 Aug 2011 20:47:00 -0500

I'd think the Ames test results ("Hey, it won't mutate you or directly give you
cancer!") wouldn't stand up to marketing.

If I had to guess, it's some sort of skin cell culture.  What were the claims
of the product?  Did it say something about collagen or skin elasticity?

If it did say something about "prevents damage from free radicals and
sunlight", then maybe it *is* based on Ames testing.  But if it's anything
else, I think it'd have to be mammalian tissue of some sort....

(SledgeHammer/9531) Many animal cell culture lines come from tumor cells; probably t...

SledgeHammer@rss.iscabbs.com — Thu, 04 Aug 2011 16:30:00 -0500

Many animal cell culture lines come from tumor cells; probably the most
commonly employed (and nearly virulent in its spread in labs, interestingly
enough) is HeLa, named for Henrietta Lacks. She's been dead for almost 60
years, but her cells live on.

Another popular line is CHO, Chinese hamster ovary cells. There are also large
numbers of insect cell culture lines (Sf9, Sf21, etc. from armyworms).

Anyway- while there are certainly many lines of mammalian cell cultures
(including just growing one's own skin in sterile culture to cover burned
areas- no stem cells required), the "in vitro testing" to which they allude
could be something as old and reliable as the Ames mutagenicity test. In short,
the Ames test uses a strain of bacteria that can live on sugars in vitro; but
they are put on a medium with a specific sugar they can't live on. The medium
also contains a chemical under test; if this chemical is a mutagen, the number
of mutations occurring in the bacterium will increase. There is a chance that
mutation will allow that organism to live on that specific sugar.

So, in one fell swoop, a single Petri plate allows one to replace hundreds-
maybe thousands- of lab animals, sacrificing little more than an autoclave run
and a few trillion bacteria.

(Xenos/9530) As I understand it, all of the above. Different companies (ther...

Xenos@rss.iscabbs.com — Thu, 04 Aug 2011 13:43:00 -0500

As I understand it, all of the above.  Different companies (there are companies
that specialise just in testing, but some of the larger cosmetic companies do
some of it in-house) have different procedures.  Also different products
require different types of test, depending on what they're supposed to do.  It
could involve cultured skin cells, or it could be wholly synthetic 'skin':
otherwise known by the catchy title of 'human epithelial tissue equivalents' or
just 'human skin equivalents'.

In any case, it certainly is nothing do with embryos.  Of course many people in
the world are idiots and would prefer to believe that scientists are creating
mutant, two-headed fairies at the bottom of the garden than anything, you know,
scientific.  So you may be fighting a losing battle.

(Mama K/9529) Ok, science types, I need some help. I sell skin care and cosme...

Mama K@rss.iscabbs.com — Thu, 04 Aug 2011 06:37:00 -0500

Ok, science types, I need some help.  I sell skin care and cosmetics for a
living.  Last night, on a training call, we received some information on a new
product that has just been released.  While the trainer was reading the product
claims and benefits, she read the phrase "Based on in vitro testing."

Well, not all of us salesfolk are the brightest bulbs in the box.  A few
immediately started freaking out thinking that the product had been tested on
embryos, on embryonic stem cells, etc.  (The company I represent was a pioneer
in the industry in refusing to test on ANIMALS, but these people think they're
suddenly going to start testing on embryos??)  I tried explaining, while on the
call, the difference between in vitro and in vivo testing, but did not have
much luck.

I emailed some information to the trainer for her to pass along as she sees
fit.  However, I couldn't find a definitive answer to one question that the
gals on the call kept asking.  I'm hoping you good people can help me out here.
 The in vitro testing of cosmetics products (and/or ingredients in said
products) that is done.....where do the cells come from that the tests are run
on?  I found one reference to cultured human skin cells being used, with those
cells being grown from skin removed during plastic surgery.  I found another
reference to the dermis and hypodermis of animals being used to culture skin
cells.

Can any of y'all offer any wisdom or insight?

(Secretary/9528) Here are notable items from conference participant tweets:

Secretary@rss.iscabbs.com — Tue, 26 Jul 2011 11:09:00 -0500


Here are notable items from conference participant tweets:

"LOL. The first author of the Modern Chemistry textbook was Charles E. DULL.
#fitting" - @DesertDiver

1991 - Lee Marek...BooM - http://www.youtube.com/watch?v=S2lxnymEBUk

(Giraffe/9527) That joke is really iNane.

Giraffe@rss.iscabbs.com — Tue, 26 Jul 2011 10:49:00 -0500

That joke is really iNane.

(Secretary/9526) And now... for the first post in this forum since December 21, 2...

Secretary@rss.iscabbs.com — Tue, 26 Jul 2011 10:29:00 -0500


And now... for the first post in this forum since December 21, 2010:

Chemistry humor (work safe):

http://i.imgur.com/N0EGB.jpg




The biennial ChemEd conference is now taking place at Western Michigan
University in Kalamazoo.  It is a conference for high school chemistry teachers
from all across the United States and Canada.  This is the first time it has
ever been held anywhere in Michigan.  Follow what some attendees are doing at:

http://twitter.com/#!/search/%23ChemEd2011

(Nightspawn/9525) Thanks!

Nightspawn@rss.iscabbs.com — Tue, 21 Dec 2010 13:55:00 -0600

Thanks!

(SledgeHammer/9524) I worked with cesium for this one DARPA project. What a pain to ...

SledgeHammer@rss.iscabbs.com — Tue, 21 Dec 2010 13:45:00 -0600

I worked with cesium for this one DARPA project. What a pain to work with; it
came in a sealed ampule, and it would liquefy as you held it in your hand. Also
worked with rubidium (and the usuals- lithium, sodium, potassium) for that
project.

(Swinia/9523) Sodium was the first to come to mind, personally.

Swinia@rss.iscabbs.com — Tue, 21 Dec 2010 13:45:00 -0600


Sodium was the first to come to mind, personally.

(Aztech/9522) Xenos> According to some sources (pubs.usgs.gov/of/2004/1432/20...

Aztech@rss.iscabbs.com — Tue, 21 Dec 2010 13:39:00 -0600

Xenos>  According to some sources (pubs.usgs.gov/of/2004/1432/2004-1432.pdf),
cesium ignites in air.

Whether it's a violent oxide reaction or reacting with humidity, I don't know.

But elemental cesium isn't as common as sodium or potassium metal in labs, so I
don't know of anyone who's worked with it directly.


I do remember visiting friends of mine who were in hard-core inorganic chem
labs in grad school, and watching them transfer stuff like odd metal-Cp
compounds that would have a flame at the end of the gas-tight syringe as they
worked.  Wacky crap  :)

Then again, they get scared looks on their faces when I talk about the
neurotoxic or teratogenic stuff I work with in biochem, so....the devil you
know.

(Xenos/9521) Like Aztech said, the one that reacts spontaneously is white pho...

Xenos@rss.iscabbs.com — Tue, 21 Dec 2010 06:03:00 -0600

Like Aztech said, the one that reacts spontaneously is white phosphorous.  It
will burst into flame in air, although sometimes if you have a big chunk of it
sometimes it'll form an oxide layer on the surface and sit there reasonably
happily for a while.  If you chip a splinter off though it'll go up nicely (did
that once, it set the floor on fire, heh).

Nitrogen triiodide reacts extremely explosively when exposed to minor shocks.
It's not the air directly, it's vibrations, but it only takes the gentlest
breeze to set that off.  It's bloody loud too.  A ball of it one millimetre
cubed will leave your ears ringing.

The alkali metals react violently with water and very rapidly with oxygen.  I
doubt any of them would explode in air, unless it was very humid air.  I've
seen sodium and potassium explode in contact with water.

(Aztech/9520) Or are you referring to stuff like the alkali metals (especially...

Aztech@rss.iscabbs.com — Mon, 20 Dec 2010 23:50:00 -0600

Or are you referring to stuff like the alkali metals (especially the higher MW
ones like rubidium) which rapidly oxidize in open air, or white phosphorus?

(SledgeHammer/9519) You mean spontaneously? Or with an ignition source? Almost any f...

SledgeHammer@rss.iscabbs.com — Mon, 20 Dec 2010 22:19:00 -0600

You mean spontaneously? Or with an ignition source? Almost any flammable solid
will give a nice kabang provided it is divided sufficiently finely, and given
an ignition source. Aluminum powder that's milled as fine as it gets (ball
milled, German black grade) is one of the best; we had a grumpy coot of an
explosives chemist- one of the best in the world- threaten to blow the place up
once or twice with a bucket of German black in the HVAC system.

(Nightspawn/9518) What chemicals/elements react explosively with air? I could hav...

Nightspawn@rss.iscabbs.com — Mon, 20 Dec 2010 20:52:00 -0600

What chemicals/elements react explosively with air?  I could have sworn my
chemistry teacher back in high school talked about some...

(Danix/9517) DHMO can kill you!

Danix@rss.iscabbs.com — Wed, 06 Oct 2010 23:48:00 -0500

DHMO can kill you!

(SledgeHammer/9516) The MSDS for compressed breathing air from Sigma used to carry t...

SledgeHammer@rss.iscabbs.com — Wed, 06 Oct 2010 20:09:00 -0500

The MSDS for compressed breathing air from Sigma used to carry the typical
warning for accidental inhalation. The other one was HPLC-grade water. They
were treating breathing air and ultra-pure water as if they were chlorine and
acetone for the purposes of exposure.

(Aztech/9515) Xenos: I just pulled up the MSDS on sodium chloride from Sigma-...

Aztech@rss.iscabbs.com — Wed, 06 Oct 2010 18:52:00 -0500

Xenos:  I just pulled up the MSDS on sodium chloride from Sigma-Aldrich,
product number S3014.  Now, I'm in Canada, and it's listing the division in
Oakville ON as the company.


But in Section 2 on page 1, under "Potential Health Effects":

Inhalation:  May be harmful if inhaled.  May cause respiratory tract irritation
Skin:  May be harmful if absorbed through skin.  May cause skin irritation
Eyes:  May cause eye irritation
Ingestion:  May be harmful if swallowed


It may be asinine, but I ain't makin' it up!

(Giraffe/9514) It's all about concentrations. There are very few toxins that ca...

Giraffe@rss.iscabbs.com — Wed, 06 Oct 2010 17:51:00 -0500

It's all about concentrations. There are very few toxins that can't be
tolerated at some level of dilution.

(Xenos/9513) One of the other chemistry teachers says there are three things ...

Xenos@rss.iscabbs.com — Wed, 06 Oct 2010 17:18:00 -0500

One of the other chemistry teachers says there are three things that smell like
almonds, methyl benzoate, hydrogen cyanide, and almonds.  If you're not sure,
send someone else into the room first ;-)

(Danix/9512) why? it smells like sour almondssssssssssss...

Danix@rss.iscabbs.com — Wed, 06 Oct 2010 17:16:00 -0500

why? it smells like sour almondssssssssssss...

(Xenos/9511) Yeah... actually sodium chloride has no such designation. Becau...

Xenos@rss.iscabbs.com — Wed, 06 Oct 2010 17:01:00 -0500

Yeah... actually sodium chloride has no such designation.  Because that would
be silly.  Such things are mainly urban legends :-)  Only volatile chemicals
CAN have anything 'by inhalation'.

Still after some discussion with a couple of other chemists we decided that a
gentle one-off sniff of something so labelled would be perfectly safe.  It
really applies to persistent exposure.

Hydrogen cyanide... I don't think I'll take any chances ;-)

(SledgeHammer/9510) The LCt50 of hydrogen cyanide is 2500 to 5000 mg min/m^3. That w...

SledgeHammer@rss.iscabbs.com — Tue, 05 Oct 2010 20:51:00 -0500

The LCt50 of hydrogen cyanide is 2500 to 5000 mg min/m^3. That works out to 2.5
to 5 mg per liter. Given that a liter of air weighs ~1.2 grams, that's a fairly
high concentration. Just a whiff won't kill you.

The cyanide that you did inhale would be metabolized and removed quickly. Now,
something like phosgene or another vesicant? Forget about it.

(Aztech/9509) Depends on what it is: I think sodium chloride has the "harmful...

Aztech@rss.iscabbs.com — Tue, 05 Oct 2010 20:42:00 -0500

Depends on what it is:  I think sodium chloride has the "harmful by inhalation"
designation, since you shouldn't snort it.

I'd still err on the side of caution.

(Xenos/9508) If something says 'harmful by inhalation' do you think it's prob...

Xenos@rss.iscabbs.com — Tue, 05 Oct 2010 14:10:00 -0500

If something says 'harmful by inhalation' do you think it's probably ok to
suggest someone simply smell it?

Going by the chemicals that have that classification it seems so to me.  The
ones that are nasty are (logically) labelled 'toxic by inhalation' or 'very
toxic by inhalation' (that'd be cyandide ;-)

(Xenos/9507) Not if they have ions in them with partially-filled d sub-shells...

Xenos@rss.iscabbs.com — Wed, 15 Sep 2010 15:32:00 -0500

Not if they have ions in them with partially-filled d sub-shells :-)

(SledgeHammer/9506) That's how useful they are. All those years in academia and indu...

SledgeHammer@rss.iscabbs.com — Tue, 14 Sep 2010 20:58:00 -0500

That's how useful they are. All those years in academia and industry, and the
only time the subject of orbitals and electron density ever came up was during
a discussion as to why so many crystalline compounds were white.

(Aztech/9505) Well, by definition, nodal planes are areas of zero electron den...

Aztech@rss.iscabbs.com — Tue, 14 Sep 2010 19:08:00 -0500

Well, by definition, nodal planes are areas of zero electron density.  I
remember a segment in quantum P chem where we had to add together wavefunction
(?) data for a series of mostly aromatic N-heterocycles of various sizes. 
There were areas in the electron clouds above and below the plane of the ring
where there was zero probability of having an electron, and how moving from one
side of the nodal plane would switch the sign of the density, thereby having an
effect on how something would bond to it.

Do I remember the term "nodal plane" in high school chemistry?  No.  But it's
also been almost 20 years since I took high school chem, so my memory might be
faulty.  I do remember going through how p and d orbitals did have areas of no
electron density.

(Xenos/9504) That's interesting, I don't remember specifically covering nodal...

Xenos@rss.iscabbs.com — Tue, 14 Sep 2010 17:07:00 -0500

That's interesting, I don't remember specifically covering nodal planes in my
degree course... (nodes, yes).  What's the relevance?  Presumably they have an
impact on the type of bonding?

(SledgeHammer/9503) I suspect it has little to no use beyond that of satisfying the ...

SledgeHammer@rss.iscabbs.com — Tue, 14 Sep 2010 17:06:00 -0500

I suspect it has little to no use beyond that of satisfying the author of the
textbook. He probably put nodal planes in a paper that failed peer review, so
now he feels compelled to include it in some textbook chapter. It has the same
utility as adding up the temperature of stars as per Richard Feynman in his
excoriation of textbooks.

(SledgeHammer/9501) Yep. It's 8. She has an online chemistry thing; got the answer w...

SledgeHammer@rss.iscabbs.com — Sun, 12 Sep 2010 23:56:00 -0500

Yep. It's 8. She has an online chemistry thing; got the answer wrong the first
time, but (after figuring the same thing- 4 ways, two planes each) 8 is the
correct answer.

(Aztech/9500) Eight?

Aztech@rss.iscabbs.com — Sun, 12 Sep 2010 10:35:00 -0500

Eight?

The 5 d orbitals are xy, xz, yz, z^2, and x^2-y^2.  All but z^2 are four-lobed,
with nodal planes between adjacent pairs of lobes.  Think of it like a compass
rose:  N E S W being where the lobes are located, and the diagonals SW-NE and
NW-SE being the nodal planes.  So, 4x2 = 8.

The z^2 orbital is a dumbbell with a torus:  think of an hourglass with a donut
around the narrow point.  While there are points and areas within this orbital
that have zero electron density, there are no nodal *planes* you can draw
through the entire orbital.  Therefore, 8+0=8.

(SledgeHammer/9499) My neice is taking baby chem, and asked me about nodal planes. B...

SledgeHammer@rss.iscabbs.com — Sat, 11 Sep 2010 23:41:00 -0500

My neice is taking baby chem, and asked me about nodal planes. Being an
analytical kind of guy, I have just about zero interest for atomic orbitals,
and never even HEARD of "nodal planes" until today.

The question is: how many nodal planes are present in a complete set of 3d
orbitals. She thought it would be 2 or 4, but it's neither. The list of
possible answers is 5, 3, 20, 8, 10, and 16. Any help?

(Egregious/9498) Hm, maybe I judged too soon.

Egregious@rss.iscabbs.com — Mon, 21 Dec 2009 14:24:00 -0600


Hm, maybe I judged too soon.

A kilogram of a good battery has about 40 watt-hours per kilogram, or
40 * 3600 = 140 Kilojoules.

To take 1 kg of a 1-J/K/g material from 0C to 100C is 100 Kilojoules.

So for an electric car in winter, it could keep a significant amount of
energy stored in the inside of the car and the engine while still hooked
up to the power grid.  On the downside, there's a lot of places you need
to warm up if you start cold, or even if you aren't insulated well.

(SledgeHammer/9497) Sorry- didn't mean to go unitless, the physical scientist's equi...

SledgeHammer@rss.iscabbs.com — Fri, 18 Dec 2009 15:28:00 -0600

Sorry- didn't mean to go unitless, the physical scientist's equivalent of the
dream where you go to work without your pants. That should be J/K/g. The
highest heat capacity of any substance is hydrogen gas, at 14.3 J/K/g. I seem
to recall some types of nuclear reactors using hydrogen gas as the heat
exchange medium. May as well make it radioactive AND explosives.

(Egregious/9496) wow, that's pretty crappy compared to a battery, which isn't sta...

Egregious@rss.iscabbs.com — Fri, 18 Dec 2009 15:16:00 -0600

wow, that's pretty crappy compared to a battery, which isn't starting out
as the epitome of energy density anyway

(SledgeHammer/9495) IIRC, heat capacties of ceramics are under 1 J/g, or about 1/5 t...

SledgeHammer@rss.iscabbs.com — Fri, 18 Dec 2009 14:54:00 -0600

IIRC, heat capacties of ceramics are under 1 J/g, or about 1/5 that of liquid
water. Just pulling a number out of thin air- titanium carbide, at about 0.83
to 0.85 J/g. Not all that good.

(Egregious/9494) What's the heat capacity of the ceramic used in space heaters?

Egregious@rss.iscabbs.com — Fri, 18 Dec 2009 11:48:00 -0600

What's the heat capacity of the ceramic used in space heaters?

I'm thinking how much thermal energy could be safely stored in, say, 1kg of
material in an electric car hooked up to the power grid, before driving away.

(Xenos/9493) Ah well, in that case, you're welcome :-)

Xenos@rss.iscabbs.com — Thu, 15 Oct 2009 16:08:00 -0500

Ah well, in that case, you're welcome :-)
(What's so wrong with smilie faces?)

(Vodomin/9492) On the grounds that I would have to pack myself up in a UFO shap...

Vodomin@rss.iscabbs.com — Thu, 15 Oct 2009 16:00:00 -0500

On the grounds that I would have to pack myself up in a UFO shaped balloon and
launch myself into the atmosphere if I did send someone a smilie face of that
nature, no . . .  you don't get a smilie face.

That said, I do greatly appreciate your suggestions!  I need to look the links
up still when I get home.  Also, I received a few suggestions by mail.  I
appreciate those as well.

(Xenos/9491) Man, I write a whole page of experiments, with helpful links, an...

Xenos@rss.iscabbs.com — Thu, 15 Oct 2009 15:44:00 -0500

Man, I write a whole page of experiments, with helpful links, and I don't even
get a smilie face?  ;-)

(Egregious/9490) fire and explosions are always cool

Egregious@rss.iscabbs.com — Thu, 15 Oct 2009 15:18:00 -0500

fire and explosions are always cool

(Vodomin/9489) Thanks for the suggestions.

Vodomin@rss.iscabbs.com — Thu, 15 Oct 2009 15:15:00 -0500

Thanks for the suggestions.

(SledgeHammer/9488) And glow sticks. Separate the two components, add A to B. They c...

SledgeHammer@rss.iscabbs.com — Thu, 15 Oct 2009 14:05:00 -0500

And glow sticks. Separate the two components, add A to B. They come in colors
other than green, too.

(Xenos/9487) I have many :-)

Xenos@rss.iscabbs.com — Thu, 15 Oct 2009 13:51:00 -0500

I have many :-)

1) Mix cornflower with a little water and some food colouring.  Alien blood -
it goes solid when you hit it!

2) Mix PVA glue with borax (you should be able to get it, it's used in cleaning
supplies).  If you add lots of borax and a little custard powder (and food
colouring), you'll get bouncy balls (erm, bouncy brains? ;-)  If you use less,
then icky slime, ewwwww!

3) You can make witch's fireballs by 'snapping' orange peel into a candle
flame.  See:
www.thenakedscientists.com/HTML/content/kitchenscience/exp/fruit-fireballs/
(totally work safe despite the name, honest)

4) Do the magic relighting-wand by adding a little dried yeast to some hydrogen
peroxide.  Put a glowing taper into the gas that's produced (it's oxygen) and
it will relight, ooooh :-)

5) If you do get hold of solid CO2, make sure you add some indicator to the
water before you plop the CO2 in, and watch the magic colour-changing bubbling
potion!  (If you can't get universal indicator, make some cabbage indicator,
see: http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm

6) Magic writing would be something else for the kids to do themselves.  Plain
old lemon juice should work just fine, or bicarb, or more here:
www.thenakedscientists.com/HTML/content/kitchenscience/food/exp/invisible-inks/

Erm, well, that should keep them busy for the evening I'd imagine :-)

(Vodomin/9486) I understand and can explain a lot of kitchen chemistry (from a ...

Vodomin@rss.iscabbs.com — Thu, 15 Oct 2009 10:19:00 -0500

I understand and can explain a lot of kitchen chemistry (from a laymen's
perspective).   I'd really like to do something for the neighborhood kids for
halloween.  I want to put together a halloween story with 3 or 4 chemistry
experiments worked in (as sort of magic).  I'll figure out the story.  I had
considered a pH indicator experiment, something with dry ice (always a pleaser)
and maybe some hot ice (which I've seen but never done).

Does anyone have any suggestions?

It would have to involve materials I can get local or VERY EASILY online.

(Xenos/9485) The biggest AS subject at my school is officially Chemistry, and...

Xenos@rss.iscabbs.com — Sat, 05 Sep 2009 17:15:00 -0500

The biggest AS subject at my school is officially Chemistry, and since I'm Head
of Chemistry, go me! ;-)

('AS' is the level that comes after basic high school qualifications, roughly
equivalent to what you guys would call 11th grade.  Until that point, science
is a compulsory subject for all students, but after that they can drop it - so
for a science to be the biggest subject is an achievement :-)

(Xenos/9484) If it's phase imaged, it might indicate that the molecule is fle...

Xenos@rss.iscabbs.com — Tue, 01 Sep 2009 14:44:00 -0500

If it's phase imaged, it might indicate that the molecule is flexing more at
the ends...

(Darkhaven/9483) so, per this story:

Darkhaven@rss.iscabbs.com — Tue, 01 Sep 2009 09:49:00 -0500

so, per this story:
http://www.dailymail.co.uk/sciencetech/article-1209726/Single-molecule-million-
times-smaller-grain-sand-pictured-time.html
of ibm imaging pentacene, why do you see the bonds and not the actual atoms?
and what is making the ends 'brighter'?

(Xenos/9482) Thanks for the sulfanilamide from aniline suggestion SledgeHamme...

Xenos@rss.iscabbs.com — Fri, 28 Aug 2009 07:02:00 -0500

Thanks for the sulfanilamide from aniline suggestion SledgeHammer, that looks
quite promising and I found a complete prac method on the net :-)
http://www.chem.missouri.edu/Chem2140/Sulfanilamide.pdf

(Xenos/9481) I can't make explosives :-) Well, I COULD, but I'm not going to...

Xenos@rss.iscabbs.com — Tue, 25 Aug 2009 19:23:00 -0500

I can't make explosives :-)  Well, I COULD, but I'm not going to, because I
want to keep my job and I also fear losing a limb due to careless teenagers not
paying attention to what they're doing.  Mind you, my labs ARE grotty and could
do with demolishing ;-)

(SledgeHammer/9480) Sulfanilamide from aniline. If feeling adventurous (and, there i...

SledgeHammer@rss.iscabbs.com — Tue, 25 Aug 2009 16:13:00 -0500

Sulfanilamide from aniline. If feeling adventurous (and, there in the UK,
liable to be arrested), isolation of glycerol followed by nitrification. Highly
recommended: Phokion Naoum's text on the subject.