This is a question for a chemistry major or instructor?

Question

I am taking a chemistry class towards my BSN and the instructor posed a question to us before the end of class last week and it was: What is the correlation between the boiling point of water and the properties of a bullet proof vest? I have searched on yahoo and found something about intermolecular changes but I want an expert on the subject to help me out it was not an assignment but I just want to impress the instructor with the correct answer. Thanks in advance.

Answer 1

Gervald is right

Kevlar is a polymer of terephthalic acid and p-phenylene diamine:

NH2-Ph-NH2 + HOOC-Ph-COOH (in H2SO4) -->

--(NHCO-Ph-CONH-Ph--)--

The hydrogen bonding between the chains is SO strong that after the polymer is precipitated from the sulfuric acid is can NEVER be dissolved again (IN ANYTHING!!).

So what your teacher is alluding to is H-bonding forces.

Intermolecular H-Bonding in a small molecule like water and the incredibly strong intermolecular H-bonding between the chains of the polymer chains in kevlar.

Answer 2

The correlation is the strength of the forces. Water has hydrogen bonding, which is very strong, and makes water have an incredibly high boiling point for the size of the molecule. Kevlar also has strong forces (it's a composite material) which makes it difficult to get a bullet through!

Answer 3

pretty much i agree with gervald

Water has hydrogen bonding. Water itself is a hydrogen bonded to an oxygen bonded to another hydrogen.....but then each of these water molecules are bonded to eachother through hydrogen bonding.

The Hydrogen from one molecule weakly bonds to the oxygen of another water molecule. Bond i guess is the right word to use, but "interaction" might be better.

This basically makes your glass of water "stronger" than it should be...hmm....trying to think of how to say this and then relate it to teh kevlar.

Had there been no hydrogen bonding, water would boil at a lower temperature.....

So the liquid water absorbs a lot of energy before it goes through a phase change to a gas.


Basically what kevlar does is that it absorbs energy. IF you got shot while wearing a t-shirt or set on fire, your shirt absorbs some of teh energy of the bullet...or hte fire.....but not much and its basically worthless.

Kevlar can absorb that energy and dissipate it before the bullet goes through...or the fire can break up the molecular bonds. Kevlar also has Hydrogen bonding taking place.
Here is a picture
http://en.wikipedia.org/wiki/Kevlar

Just remember when you cut something or break something, you are breaking molecular bonds. You're applying enough energy for the bonds to break. You're not ripping up a molecule itself, but ripping up its connection to the next molecule.

Short answer is that there is hydrogen bonding taking place that adds strength to the material.

Answer 4

Organic Chemistry is only required for majors that deal heavily with chemistry or life sciences. Chemistry is often one of the required science courses for ANY A.A. or B.A. Chemistry is almost always required for any science or engineering B.S.