textex
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Registered: 29-3-2011
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Exams coming up
Hiya,
i got a chemistry exam coming up in a few days, and i got a feeling i might have to talk abit of the chemicals properties of water. I feel pretty well
prepared, but its always nice to have something to impress the censor with. And my book doesent really go very far out on the properties of water. So
i wondered if anyone have a few links they feel like throwing out?
Especially on the formation and structure of hydrates.
Thanks in advance!
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Adas
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Search for such things as superheated or supercooled water. Pretty interesting, I think. You can also mention so-called "methane hydrate" http://en.wikipedia.org/wiki/Methane_clathrate
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JibbyDee
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I read this page:
http://dl.clackamas.edu/ch105-03/examples1.htm
that compares the solubility of various compounds in water with their solubility in carbon tetrachloride. You should mention that water has the
unusual property of its liquid phase being more dense than its solid phase due to hydrogen bonding exhibited by liquid water molecules. The property
is why lakes "freeze over" forming an insulative blanket of ice on the top of lakes which is what allows the aquatic lifeforms in it to survive cold
winters. It is also the reason pipes often burst when the temperature gets so cold that the water inside them freezes and why ice cubes float instead
of sink.
To impress them, you could talk about hydrogels:
http://www.biomaterials.org/week/bio17.cfm
they're basically water insoluble polymers that form a molecular cage which entraps water so you end up with a substance that is actually 99% liquid
but in many ways mimics the properties of a solid.
[Edited on 10-12-2011 by JibbyDee]
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francis
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Hi,
You should check out Peter Wothers' show "Just Add Water": he does a bunch of excellent demonstrations while explaining the various properties of
water.
He highlights some very cool features of the molecule.
http://fora.tv/2009/08/18/Peter_Wothers_Just_Add_Water
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